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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 121 journals)
Showing 1 - 30 of 30 Journals sorted by number of followers
AIAA Journal     Hybrid Journal   (Followers: 1188)
SpaceNews     Free   (Followers: 826)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 772)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 609)
Acta Astronautica     Hybrid Journal   (Followers: 493)
Advances in Space Research     Full-text available via subscription   (Followers: 458)
Aviation Week     Full-text available via subscription   (Followers: 436)
Aerospace Science and Technology     Hybrid Journal   (Followers: 428)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 384)
Journal of Aircraft     Hybrid Journal   (Followers: 335)
Control Systems     Hybrid Journal   (Followers: 314)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 278)
Journal of Navigation     Hybrid Journal   (Followers: 277)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 258)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 204)
Space Science International     Open Access   (Followers: 198)
Space Science Reviews     Hybrid Journal   (Followers: 97)
International Journal of Aerospace Engineering     Open Access   (Followers: 82)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 80)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 69)
Advances in Aerospace Engineering     Open Access   (Followers: 69)
Propulsion and Power Research     Open Access   (Followers: 68)
Aerospace     Open Access   (Followers: 60)
Space Safety Magazine     Free   (Followers: 51)
Space Research Today     Full-text available via subscription   (Followers: 48)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 46)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 40)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 39)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 37)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 34)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 34)
International Journal of Aerospace Sciences     Open Access   (Followers: 32)
Journal of Aeronautics & Aerospace Engineering     Open Access   (Followers: 31)
Space Policy     Hybrid Journal   (Followers: 30)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 29)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 27)
Journal of Space Weather and Space Climate     Open Access   (Followers: 27)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 24)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 24)
Artificial Satellites     Open Access   (Followers: 23)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 23)
Annual of Navigation     Open Access   (Followers: 22)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 22)
Chinese Journal of Aeronautics     Open Access   (Followers: 21)
Nonlinear Dynamics     Hybrid Journal   (Followers: 20)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 19)
Aerospace Scientific Journal     Open Access   (Followers: 18)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 18)
Journal of Aerodynamics     Open Access   (Followers: 18)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 17)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 17)
Aviation     Open Access   (Followers: 17)
International Journal of Space Structures     Full-text available via subscription   (Followers: 17)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
Fatigue of Aircraft Structures     Open Access   (Followers: 15)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 13)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 12)
Aeronautical Journal, The     Hybrid Journal   (Followers: 12)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 12)
Journal of Airline and Airport Management     Open Access   (Followers: 12)
Elsevier Astrodynamics Series     Full-text available via subscription   (Followers: 12)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 11)
Air Force Magazine     Full-text available via subscription   (Followers: 11)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 11)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 11)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 10)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 10)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 9)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 9)
Journal of Aeronautical Materials     Open Access   (Followers: 9)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 9)
Population Space and Place     Hybrid Journal   (Followers: 9)
International Journal of Aviation Management     Hybrid Journal   (Followers: 9)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 8)
Air Medical Journal     Hybrid Journal   (Followers: 8)
Advances in Aerospace Science and Technology     Open Access   (Followers: 8)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 7)
Journal of Aerospace Technology and Management     Open Access   (Followers: 7)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 7)
RocketSTEM     Free   (Followers: 6)
New Space     Hybrid Journal   (Followers: 6)
Aerospace Systems     Hybrid Journal   (Followers: 6)
International Journal of Turbo and Jet-Engines     Hybrid Journal   (Followers: 6)
Unmanned Systems     Hybrid Journal   (Followers: 5)
Civil Aviation High Technologies     Open Access   (Followers: 5)
Cosmic Research     Hybrid Journal   (Followers: 5)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 5)
Aviation Advances & Maintenance     Open Access   (Followers: 5)
Astrodynamics     Hybrid Journal   (Followers: 4)
Life Sciences in Space Research     Hybrid Journal   (Followers: 4)
Space and Polity     Hybrid Journal   (Followers: 4)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 4)
Aerospace technic and technology     Open Access   (Followers: 3)
Investigación Pecuaria     Open Access   (Followers: 3)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
ASTRA Proceedings     Open Access   (Followers: 3)
npj Microgravity     Open Access   (Followers: 3)
Journal of Astrobiology & Outreach     Open Access   (Followers: 3)
Journal of Spatial Science     Hybrid Journal   (Followers: 3)
Journal of KONBiN     Open Access   (Followers: 3)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Ciencia y Poder Aéreo     Open Access   (Followers: 2)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 2)
Microgravity Science and Technology     Hybrid Journal   (Followers: 2)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
MAD - Magazine of Aviation Development     Open Access   (Followers: 2)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 2)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Mekanika : Jurnal Teknik Mesin i     Open Access   (Followers: 1)
Technical Soaring     Full-text available via subscription   (Followers: 1)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 1)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 1)
Transport and Aerospace Engineering     Open Access   (Followers: 1)
Open Aerospace Engineering Journal     Open Access   (Followers: 1)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 1)
Perspectives of Earth and Space Scientists i     Open Access  

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Similar Journals
Journal Cover
IEEE Transactions on Aerospace and Electronic Systems
Journal Prestige (SJR): 0.611
Citation Impact (citeScore): 3
Number of Followers: 384  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0018-9251
Published by IEEE Homepage  [229 journals]
  • IEEE Aerospace and Electronic Systems Society
    • Abstract: Provides a listing of current staff, committee members and society officers.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • From the Editor-in-Chief FEBRUARY 2021
    • Authors: Lyudmila Mihaylova;Gokhan Inalhan;
      Pages: 3 - 4
      Abstract: Presents the editorial for this issue of the publication.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • A Parallel Retrodiction Algorithm for Large-Scale Multitarget Tracking
    • Authors: Siu Lun Yeung;Sean Tager;Paul Wilson;Ratnasingham Tharmarasa;Wes Armour;Jeyarajan Thiyagalingam;
      Pages: 5 - 21
      Abstract: Kalman filter-based retrodiction plays an indispensable role in modern multitarget tracking and retrodiction (MTTR) algorithms. To this end, the Rauch–Tung–Striebel (RTS) smoother is a widely used Kalman filter-based target state smoother. With a large number of targets, MTTR algorithms, particularly with large window sizes, become very computationally intensive. If not addressed, these algorithms will not meet the requirements for tracking a large number of targets in real time. A natural approach is to parallelize these algorithms to render them useful, particularly in the context of emerging multicore platforms. However, this is nontrivial, as the governing mathematical framework of the RTS smoother, namely the dependencies between complex computations, prevents any form of parallelization. Although the MTTR component can naively be parallelized ignoring the smoothing component, the overall benefit, as we demonstrate in this article, is a fraction of the best possible benefits. In this article, by carefully reformulating the underlying mathematical framework that is necessary for retrodiction, we propose a novel, easily parallelizable RTS smoother. The proposed parallelized RTS smoother we outline in this article has best data reuse and enables the overall MTTR problem to be parallelized more efficiently. We demonstrate this on a state-of-the-art multicore processor platform using the shared-memory parallelism. Our results show that the parallel MTTR solution, which includes gating, assignment, tracking, and retrodiction, can offer nearly 150 times speed up against a fully sequential version. With excellent computational performance, our proposed RTS smoother enables very large window sizes with little or no impact on the overall performance.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Image Registration for 3-D Interferometric-ISAR Imaging Through
           Joint-Channel Phase Difference Functions
    • Authors: Byung-Soo Kang;Keewoong Lee;Kyung-Tae Kim;
      Pages: 22 - 38
      Abstract: To perform 3-D inverse synthetic aperture radar (ISAR) imaging through interferometric processing, all ISAR images should be correctly registered such that the same scatterer appears at the same position along both the range and Doppler directions. However, this condition generally does not hold in most situations because different radar view angles introduce additional angular motion errors that must be compensated. Hence, we herein propose a new ISAR registration method based on joint-channel phase difference (JC-PD) operations. From the result of the JC-PD function, JC-PD profiles are obtained, in which the locations and phases of the maximum peak contain constant and time-varying angular motions, respectively. Using our proposed method, correct ISAR registrations can be achieved in both the range and Doppler directions. In particular, compared to conventional Doppler registration methods, time-varying angular motions are more accurately compensated without the problem of cross-term phase interference. Through simulations and experiments, we verified that the proposed method yielded accurate ISAR registration results; hence, an excellent 3-D target reconstruction through interferometric ISAR imaging was demonstrated.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Constrained Robust Model Reference Adaptive Control of a Tilt-Rotor
           Quadcopter Pulling an Unmodeled Cart
    • Authors: Robert B. Anderson;Julius A. Marshall;Andrea L’Afflitto;
      Pages: 39 - 54
      Abstract: This article presents an innovative control architecture for tilt-rotor quadcopters with H-configuration transporting unknown, sling payloads. This control architecture leverages on a thorough analysis of the aircraft's equation of motion, which reveals gyroscopic effects that were not fully characterized and were disregarded while synthesizing control algorithms in prior publications. Furthermore, the proposed control architecture employs barrier Lyapunov functions and a novel robust model reference adaptive control law to guarantee a priori user-defined constraints on both the trajectory tracking error and the control input, despite poor information on the aircraft's inertial properties and the presence of unknown, unsteady payloads. Flight tests involving a quadcopter pulling an unmodeled cart by means of a thin rope of unknown length, which is slack at the beginning of the mission, verify the effectiveness of the theoretical results.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Fast Protection Levels for Fault Detection With an Application to Advanced
           RAIM
    • Authors: Juan Blanch;Todd Walter;
      Pages: 55 - 65
      Abstract: Fault detection algorithms (such as advanced RAIM) developed for aviation can be applied in situations where the probabilities of fault are arbitrarily high. However, with large probabilities, the user receiver needs to protect against a large number of fault modes (which results from the combination of simultaneous independent faults). In baseline ARAIM algorithms, the user receiver must compute a fault-tolerant position solution for each fault mode (computed using the subset of the available measurements that would not be affected by the fault mode), or at least its error covariance. After showing how to use a solution separation algorithm without computing the fault-tolerant position solutions, we present a technique to obtain upper bounds on the subset error covariance for a given subset size. This upper bound does not require the computation of every subset error covariance and can be computed without additional matrix inversions. We evaluate the potential of this technique by applying it to ARAIM scenarios.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Single-Filter Finite Fault Detection and Exclusion Methodology for
           Real-Time Validation of Plug-and-Play Sensors
    • Authors: Juan Jurado;John Raquet;Christine M. Schubert Kabban;
      Pages: 66 - 75
      Abstract: All-source navigation has become increasingly relevant over the past decade with the development of viable alternative sensor technologies. However, as the number and type of sensors informing a system increases, so does the probability of corrupting the system with sensor modeling errors, signal interference, and undetected faults. Though the latter of these has been extensively researched, the majority of existing approaches have designed algorithms centered around the assumption of simultaneously redundant, synchronous sensors with well-understood measurement models, none of which are guaranteed for all-source systems. As part of an overall all-source assured or resilient navigation objective, this research contributes a key component—validation of sensors which have questionable sensor models, in a fault-agnostic and sensor-agnostic manner, and without compromising the ongoing navigation solution in the process. The proposed algorithm combines a residual-based test statistic with the partial update formulation of the Kalman–Schmidt filter to provide a reliable method for sensor model validation that protects the integrity of the navigation solution during the validation process, all using only a single existing filter. The performance of the proposed method is validated against traditional fault detection and exclusion methods (such as normalized solution separation and conventional residual sequence monitoring) using Monte–Carlo simulations in a 2D non-Global Positioning System navigation problem with a plug-and-play position sensor.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • CDMA-MIMO Radar With the Tansec Waveform
    • Authors: Gaston Solodky;Oren Longman;Shahar Villeval;Igal Bilik;
      Pages: 76 - 89
      Abstract: This work addresses code division multiple access (CDMA) implementation of automotive multiple-input multiple-output (MIMO) radars. The tansec frequency modulation (TSFM) is proposed as a single intracoding scheme for CDMA-MIMO radars. The properties of the TSFM coding family are analyzed and two novel codeword selection algorithms are proposed. The TSFM is compared to a variety of coding families by evaluating their autocorrelation and cross-correlation properties. The considered coding families are based on phase coding: Hadamard, Gold, optimal peak to sidelobe; and frequency coding: piecewise linear frequency modulated. Properties of the coding families are analyzed with a variety of novel criteria, which are especially useful for CDMA-MIMO radars. The performance of the CDMA-MIMO radar with different coding families is evaluated via simulations of practical multitarget automotive scenarios. It is shown that the frequency-based TSFM coding family outperforms the other considered coding families in terms of their cross-correlation properties.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Autonomous Recovery of a Fixed-Wing UAV Using a Line Suspended Between Two
           Multirotor UAVs
    • Authors: Mads Friis Bornebusch;Tor Arne Johansen;
      Pages: 90 - 104
      Abstract: This article presents an autonomous recovery system for fixed wing unmanned aerial vehicles (UAVs) which is using a line suspended between two multirotor UAVs to catch a line with a hook hanging from a fixed-wing UAV. This method of recovery is particularly suitable for recovery in space constrained areas such as on small ships. A control system is presented for the proposed recovery concept and the concept is validated through experiments. The results include 17 test runs to characterize control accuracy, followed by three successful recoveries. With the selected equipment and tuning values, the multirotors were able to track the fixed-wing UAV with a mean error of 0.8 m at the moment the catch would have happened in the 17 test runs. The margins for missing for the three recoveries were 1.0–2.1 m showing that this recovery method is robust.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Optimal Energy Utilization for a Solar-Powered Aircraft Using
           Sliding-Mode-Based Attitude Control
    • Authors: Vijay Shankar Dwivedi;Salahudden;Dipak K. Giri;Ajoy Kanti Ghosh;G. M. Kamath;
      Pages: 105 - 118
      Abstract: In this article, an energy optimal dynamic attitude for a solar-powered aircraft is determined and implemented using the finite-time sliding-mode approach. A nonlinear constrained optimization technique has been considered to determine the optimal attitude of the aircraft for given a geographical location, solar position, heading direction, and other flight conditions for clear sky conditions. The optimization is performed so as to travel in the fastest possible way from one location to another location without utilizing the battery power, provided the solar energy is sufficient for the flight. The gain in the velocity due to the attitude optimization is validated with the test flight results of solar unmanned aerial vehicle (UAV) Maraal, which demonstrate the efficacy of the approach proposed here. Computational fluid dynamics (CFD) simulation is carried out to estimate aerodynamic forces acting on the aircraft at different sideslip angles. The developed aircraft dynamics incorporates the nonlinearities associated with relatively large aileron and rudder deflections. To obtain the desired attitude, a sliding-mode-based control scheme is considered. A power rate reaching law is applied to avoid chattering in the controls. Finite-time stability of the closed-loop system is discussed and it is shown that the attitude angles reach the desired values in finite time.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Distributed Game Strategy for Formation Flying of Multiple Spacecraft With
           Disturbance Rejection
    • Authors: Jianqing Li;Sai Chen;Chaoyong Li;Feng Wang;
      Pages: 119 - 128
      Abstract: This article investigates a distributed game strategy for formation control of multispacecraft subjected to nonlinear dynamics and $J_2$ perturbations. In the proposed problem, each spacecraft is devoted to minimize its own performance cost using only local information, whereas the overall formation system attempts to seek an optimized decision based on communication topology. Therefore, in our scheme, the formation control problem can be treated using a Nash strategy. A worst case Nash strategy is proposed against the disturbance defined as a player, and we prove rigorously that an open-loop Nash equilibrium exists in the underlying problem. Then, a distributed terminal state observer is introduced to facilitate the local implementation of the proposed Nash strategy. Simulation results verified the performance of the proposed scheme.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Model-Based Robust Transient Control of Reusable Liquid-Propellant Rocket
           Engines
    • Authors: Sergio Pérez-Roca;Julien Marzat;Hélène Piet-Lahanier;Nicolas Langlois;Marco Galeotta;François Farago;Serge Le Gonidec;
      Pages: 129 - 144
      Abstract: Reusable liquid-propellant rocket engines (LPREs) imply more demanding robustness requirements than expendable ones due to their extended capabilities. Therefore, the goal of this article was to develop a control loop adapted to all the operating phases of LPRE, including transients, and robust to internal parametric variations. First, thermo-fluid-dynamic simulators representative of the gas-generator-cycle engines were built. These simulators were subsequently translated into nonlinear state-space models. Based on these models, the continuous subphase of the start-up transient is controlled to track precomputed reference trajectories. Beyond the start-up, throttling scenarios are managed with end-state-tracking algorithm. Model predictive control has been applied in a linearised manner with robustness considerations to both scenarios, in which a set of hard state and control constraints must be respected. Tracking of pressure (thrust) and mixture-ratio operating points within the design envelope is achieved in simulation while respecting constraints. Robustness to variations in the predominant parameters, to external state perturbations, and to the possible impact of an observer on the loop, is demonstrated.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • On the Stability Analysis of Deep Neural Network Representations of an
           Optimal State Feedback
    • Authors: Dario Izzo;Dharmesh Tailor;Thomas Vasileiou;
      Pages: 145 - 154
      Abstract: Recent works have shown that the optimal state feedback for deterministic, nonlinear autonomous systems can be approximated by deep neural networks. In this article, we consider the stability of nonlinear systems controlled by such a network representation of the optimal feedback. First, we show that principal methods from stability theory readily applies. We then propose a novel method based on differential algebra techniques to study the robustness of a nominal trajectory with respect to perturbations of the initial conditions. It is, to the best of our knowledge, the first time that differential algebraic techniques are shown to allow for the high-order analysis of motion stability for a nonlinear system in general and for a neurocontrolled system in particular. We exemplify the proposed method in the 2-D case of the optimal control of a quadcopter and demonstrate it for different neural network architectures.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Tradespace Analysis of GNSS Space Segment Architectures
    • Authors: Filipe Pereira;Daniel Selva;
      Pages: 155 - 174
      Abstract: Global navigation satellite systems (GNSS) provide ubiquitous, continuous, and reliable positioning, navigation, and timing information around the world. However, GNSS space segment design decisions have been based on the precursor Global Positioning System, which was designed in the 1970s. This article revisits those early design decisions in view of major technological advancements and new GNSS environmental threats. The rich tradespace between user navigation error (UNE) performance and constellation deployment costs is explored and conclusions are complemented by sensitivity analysis and association rule mining. This article finds that constellations at an orbit altitude of ∼2 earth radii can outperform existing GNSS in terms of cost, robustness, and UNE. These insights should be taken into account when designing future generations of GNSS.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Recursive Extended Instrumental Variable Based LCMV Beamformers for Planar
           Radial Coprime Arrays Under Spatially Colored Noise
    • Authors: Jian-Qiang Lin;Shing-Chow Chan;
      Pages: 175 - 189
      Abstract: This article proposes a new recursive linearly constrained minimum variance (LCMV) beamformer based on the extended instrumental variable (EIV) method for planar radial coprime arrays (PRCAs) under spatially colored noise. The proposed recursive LCMV beamformer is able to deal with multiple constraints with high precision and low complexity and can be applicable to various array geometrical configurations. Taking advantage of the EIV vector, the proposed beamformer can effectively combat the additive color noise with unknown noise covariance matrix. We develop our recursive LCMV beamformer based on the square-root (SR) EIV algorithm due to its improved numerical stability than the conventional EIV-based algorithms. Furthermore, we studied a class of planar arrays called PRCAs, which consists of a set of linear coprime arrays arranged radially at various azimuth angles. The coprime array property is utilized to enlarge the array aperture leading to higher resolution and stronger interference rejection and it offers additional flexibility in the tradeoffs between array complexity and performance. Simulation results demonstrate that the proposed recursive SREIV-based LCMV beamformer outperforms the conventional QR decomposition based LCMV beamformers in the resolution and suppression of interferences under various scenarios. The PRCAs tested outperform the uniform rectangular arrays with the same number of elements. Moreover, better performance can be achieved with more linear subarrays at the expense of increased complexity.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Decentralized Automotive Radar Spectrum Allocation to Avoid Mutual
           Interference Using Reinforcement Learning
    • Authors: Pengfei Liu;Yimin Liu;Tianyao Huang;Yuxiang Lu;Xiqin Wang;
      Pages: 190 - 205
      Abstract: Nowadays, mutual interference among automotive radars has become a problem of wide concern. In this article, a decentralized spectrum allocation approach is presented to avoid mutual interference among automotive radars. Although decentralized spectrum allocation has been extensively studied in cognitive radio sensor networks, two challenges are observed for automotive sensors using radar. First, the allocation approach should be dynamic as all radars are mounted on moving vehicles. Second, each radar does not communicate with the others so it has quite limited information. A machine learning technique, reinforcement learning, is utilized because it can learn a decision-making policy in an unknown dynamic environment. As a single radar observation is incomplete, a long short-term memory recurrent network is used to aggregate radar observations through time so that each radar can learn to choose a frequency subband by combining both the present and past observations. Simulation experiments are conducted to compare the proposed approach with other common spectrum allocation methods such as the random and myopic policy, indicating that our approach outperforms the others.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Fuzzy-Logic-Based Robust Attitude Control of Networked Spacecraft via
           Event-Triggered Mechanism
    • Authors: Shidong Xu;Zhengtao Wei;Zheng Huang;Hao Wen;Dongping Jin;
      Pages: 206 - 226
      Abstract: This article studies the robust fuzzy attitude control strategy for the networked spacecraft consisting of physically independent modules that interact through network communication. The effects of inertia uncertainties, delayed feedback, actuator saturation, and external disturbances are simultaneously taken into account when designing the attitude control law. Based on aperiodic sampling, an adaptive event-triggered scheme avoiding Zeno phenomenon naturally is introduced to reduce the communication burden of network. By representing spacecraft kinematics and dynamics with Takagi–Sugeno fuzzy model, a robust fuzzy controller with $mathcal {L}_infty$-gain performance is newly developed to fulfill the attitude stabilization of networked spacecraft under complex constraints. Moreover, a novel Lyapunov functional is constructed to perform the stability analysis and controller synthesis of the resulting closed-loop system. The main results of this article are formulated in terms of linear matrix inequalities, which can be easily resolved by standard software. Finally, simulation results are presented to validate the effectiveness of the proposed attitude control strategy.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • A Comparative Performance Analysis of GPS L1 C/A, L5 Acquisition and
           Tracking Stages Under Polar and Equatorial Scintillations
    • Authors: Caner Savas;Gianluca Falco;Fabio Dovis;
      Pages: 227 - 244
      Abstract: This article provides a comparative performance analysis of different acquisition and tracking methods of GPS L1 C/A and GPS L5 signals testing their robustness to the presence of scintillations in the propagation environment. This article compares the different acquisition methods in terms of probabilities of detection/false alarm, peak-to-noise floor ratios for the acquired signal and execution time, assessing the performance loss in the presence of scintillations. Moreover, robust tracking architectures that are optimized to operate in a harsh ionospheric environment have been employed. The performance of the carrier tracking methods, namely, traditional phase-locked loop (PLL) and Kalman filter based-PLL, have been compared in terms of the standard deviation of Doppler estimation, phase error, phase lock indicator (PLI), and phase jitter. The article is based on real global navigation satellite systems (GNSS) signals affected by significant phase and amplitude scintillation effects, collected at the South African Antarctic research base (SANAE IV) and Brazilian Centro de Radioastronomia e Astrofisica Mackenzie (CRAAM) monitoring stations. Performance is assessed exploiting a fully software GNSS receiver, which implements the different architectures. The comparative analysis allows to choose the best setting of the acquisition and tracking parameters, in order to allow the operation of signal acquisition and tracking at a required performance level under scintillation conditions.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • INS/Odometer Land Navigation by Accurate Measurement Modeling and
           Multiple-Model Adaptive Estimation
    • Authors: Wei Ouyang;Yuanxin Wu;Hongyue Chen;
      Pages: 245 - 262
      Abstract: Land vehicle navigation based on the inertial navigation system (INS) and odometers (ODs) is a classical autonomous navigation application and has been extensively studied over the past several decades. In this article, we seriously analyze the error characteristics of the OD pulses and investigate three types of OD measurement models in the INS/OD integrated system. Specifically, in the pulse velocity model, a preliminary Kalman filter is designed to obtain an accurate vehicle velocity from the accumulated pulses; the pulse increment model is accordingly obtained by integrating the pulse velocity; a new pulse accumulation model is proposed by augmenting the traveled distance into the system state. The three types of measurements, along with the nonholonomic constraint, are implemented in the standard extended Kalman filter. In view of the motion-related pulse error characteristics, the multiple model adaptive estimation (MMAE) approach is exploited to further enhance the performance. Simulations and long-distance experiments are conducted to verify the feasibility and effectiveness of the proposed methods. It is shown that the standard pulse velocity measurement achieves superior performance, whereas the accumulated pulse measurement is most favorable with the MMAE enhancement.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • On the Feasibility of Orbit Determination From Gravity Gradient Invariants
    • Authors: Xiucong Sun;Hao Zhang;Pei Chen;Chao Han;
      Pages: 263 - 277
      Abstract: The capability of full-tensor gravity gradients for spacecraft orbit determination has been demonstrated in recent studies. The advantages lie in its independence from ground-based systems and its immunity against spoofing attacks. A common practice is to use Earth rotation parameters and star sensor measurements to isolate the orientation contributions to gravity gradients, which implies that the orbit determination accuracy is affected by the quality of attitude data. This article investigates the feasibility of orbit determination using gravity gradient invariants instead of full-tensor gravity gradients in order to eliminate the necessity of attitude information for frame transformation. The orbit observability is first partially explained by formulating the geometric relationship between orbital elements and geocentric distance and latitude, the latter of which can be obtained from gravity gradient invariants. Then a covariance analysis technique based on the computation of a posterior Cramér-Rao lower bound is developed to assess the orbit determination accuracy. It is assumed that the gravity gradient biases due to bandwidth limitation have been calibrated. Simulations are carried out to analyze the effects of sampling rate, orbital inclination, orbital height, and gradiometer noise level. Results show that orbit determination from gravity gradient invariants has better position accuracy in the radial direction but has degraded accuracies in the along-track and cross-track directions compared to orbit determination using full-tensor gravity gradients. The covariance analysis technique is applied to real flight data from gravity field and steady-state ocean circulation explorer. Radial, along-track, and cross-track position accuracies of 1.8, 78, and 255 m have been achieved. Future study will deal with biases in actual measurements to fulfill real orbit determination.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • A Learning Gaussian Process Approach for Maneuvering Target Tracking and
           Smoothing
    • Authors: Waqas Aftab;Lyudmila Mihaylova;
      Pages: 278 - 292
      Abstract: Model-based approaches for target tracking and smoothing estimate the infinite number of possible target trajectories using a finite set of models. This article proposes a data-driven approach that represents the possible target trajectories using a distribution over an infinite number of functions. Recursive Gaussian process, and derivative-based Gaussian process approaches for target tracking, and smoothing are developed, with online training, and parameter learning. The performance evaluation over two highly maneuvering scenarios, shows that the proposed approach provides 80 and 62% performance improvement in the position, and 49 and 22% in the velocity estimation, respectively, as compared to the best model-based filter.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Adaptive Target Separation Detection
    • Authors: Yongchan Gao;Augusto Aubry;Antonio De Maio;Hongbing Ji;
      Pages: 293 - 309
      Abstract: This article considers target separation detection (TSD) in the presence of homogeneous Gaussian interference. The problem is formulated as a hypothesis test for two typical situations: 1) the use of a low range-resolution radar or fast-track update rate; 2) the use of a high-resolution radar or low-track update rate. At the design stage, TSD tests are devised according to the generalized likelihood ratio test criterion. The computation of each decision statistic requires the solution of a semidefinite programming problem obtained leveraging the relationship among linear matrix inequalities and nonnegative trigonometric polynomials. All the obtained decision rules ensure the bounded constant false alarm rate property. At the analysis stage, the performance of some benchmark detectors is given in terms of detection and false alarm probabilities. Finally, numerical examples are provided to show the performance of the proposed tests as compared with the benchmarks as well as the gain achievable over some counterparts devised to monitor a separation event.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Experimental Results and Posterior Cramér–Rao Bound Analysis of
           EKF-Based Radar SLAM With Odometer Bias Compensation
    • Authors: Hyukjung Lee;Joohwan Chun;Kyeongjin Jeon;
      Pages: 310 - 324
      Abstract: Radar mounted on a moving vehicle returns time-varying detections corresponding to unstable scattering points, unlike optical sensors, which produce relatively stable detections. We present an efficient extended Kalman filter-based simultaneous localization and mapping (EKF-SLAM) algorithm for radar, utilizing new techniques of clustering and sifting the time-varying detections. Velocity bias and yaw rate bias, which are inherent in any odometer are also estimated and compensated using the same EKF. For theoretical performance evaluation, the posterior Cramér–Rao bound (PCRB) for SLAM with odometer bias estimation is derived and compared with the root-mean-squared errors (RMSEs), with and without bias estimation. The simulation results show that the RMSE for SLAM with bias estimation is the closest to the PCRB. The proposed algorithm is also verified experimentally with field data. The comparison with the ground truth trajectory obtained from a differential global positioning system shows that the proposed algorithm yields an accurate trajectory estimate, even under large odometer bias. Also, the real-time capability of the proposed algorithm is verified.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Multiconstrained Real-Time Entry Guidance Using Deep Neural Networks
    • Authors: Lin Cheng;Fanghua Jiang;Zhenbo Wang;Junfeng Li;
      Pages: 325 - 340
      Abstract: In this article, an intelligent predictor–corrector entry guidance approach for lifting hypersonic vehicles is proposed to achieve real-time and safe control of entry flights by leveraging the deep neural network (DNN) and constraint management techniques. First, the entry trajectory planning problem is formulated as a univariate root-finding problem based on a compound bank angle corridor, and two constraint management algorithms are presented to enforce the satisfaction of both path and terminal constraints. Second, a DNN is developed to learn the mapping relationship between the flight states and ranges, and experiments are conducted to verify its high approximation accuracy. Based on the DNN-based range predictor, an intelligent, multiconstrained predictor–corrector guidance algorithm is developed to achieve real-time trajectory correction and lateral heading control with a determined number of bank reversals. Simulations are conducted through comparing with the state-of-the-art predictor-corrector algorithms, and the results demonstrate that the proposed DNN-based entry guidance can achieve the trajectory correction with an update frequency of 20 Hz and is capable of providing high-precision, safe, and robust entry guidance for hypersonic vehicles.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Control Verifications of Space Manipulators Using Ground Platforms
    • Authors: Lijun Zong;M. Reza Emami;
      Pages: 341 - 354
      Abstract: The article discusses dynamic requirements for designing ground manipulator platforms that can be utilized to verify the performance of controllers developed for space manipulators. Dimensional analysis is used to formalize the dynamic equivalence conditions and control scaling laws between a given space manipulator and the ground manipulator to be designed, such that the space manipulator and the designed ground manipulator are dynamically equivalent. Given that, unlike its space counterpart, the ground manipulator may not have the complete six degrees of freedom for its base and it must function under the gravity effects, as well as manufacturing imprecisions in building the ground manipulator, the sensitivity of dynamic equivalence conditions to the abovementioned factors is analyzed. Furthermore, an error compensation scheme based on the feedback linearization technique is developed to make the closed-loop ground manipulator have similar joint movements to those of the space manipulator under its controller. As a result, ground-based verification experiments can be performed for the controllers that will operate on the space manipulator. The design of a ground manipulator with the error compensation scheme for a specific space manipulator is illustrated through simulations, and it is shown how the performance of a PID controller for the space manipulator can be verified using the designed ground manipulator.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Experimental Analysis of Block-Sparsity-Based Spectrum Sensing Techniques
           for Cognitive Radar
    • Authors: Augusto Aubry;Vincenzo Carotenuto;Antonio De Maio;Mark A. Govoni;Alfonso Farina;
      Pages: 355 - 370
      Abstract: Due to increasing demands for spectral resources in both communication and radar systems, the radio frequency electromagnetic spectrum is becoming more and more crowded with interfering nuisances. In order to tackle the scarcity of available spectral intervals, in recent years a multitude of sensing algorithms have been developed for improving spectrum sharing. Among these, two-dimensional (2-D) spectrum sensing can be used to obtain space–frequency electromagnetic spectrum awareness. Specifically, this approach makes it possible to optimize the spectrum usage of certain spectrum portions whose occupancy varies both temporally and spatially. In this article, we evaluate the effectiveness of certain space–frequency map recovery algorithms relying on the use of commercially available hardware. To this end, we employ an inexpensive four-channel coherent receiver, using software-defined radio components, for emitter localization. Hence, after proper calibration of the receiving system, the acquired samples are used to evaluate the performance of different signal processing strategies which exploits the inherent block-sparsity of the overall profile. At the analysis stage, results reveal the effectiveness of such algorithms.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • A Sequential Target Existence Statistic for Joint Probabilistic Data
           Association
    • Authors: Phillip L. Ainsleigh;Tod E. Luginbuhl;Peter K. Willett;
      Pages: 371 - 381
      Abstract: A sequential probability ratio test (SPRT) is introduced as a track management (TM) mechanism for the joint probabilistic data association (JPDA) multitarget tracking algorithm. The SPRT is based on an approximate target likelihood ratio that is derived from the JPDA event and association probabilities. SPRT-based TM functions are defined and compared to the joint integrated probabilistic data association (JIPDA) algorithm, including a discussion of parameter tuning for both approaches. Simulation experiments are reported for multiple closely spaced constant-velocity targets over a range of values for detection probability and clutter density. The SPRT-based algorithm achieves performance similar to JIPDA for this data, but with fewer TM parameters and a more straightforward parameter-tuning process.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Ambiguity Function Analysis of Random Frequency and PRI Agile Signals
    • Authors: Xingwang Long;Kun Li;Jing Tian;Ju Wang;Siliang Wu;
      Pages: 382 - 396
      Abstract: Random frequency and pulse repetition interval (PRI) agile (RFPA) signals bring excellent performance of electronic counter-countermeasures to radar systems and have been received considerable attention in recent years. However, the research on their ambiguity function (AF) is not comprehensive. In this article, the analytical expressions of the AF expectation and variance are given. According to the expressions, the direct relationships between the key metrics of the AF and the waveform parameters of RFPA signals are specified. The results in this article are verified by Monte Carlo simulations and provide some insights into RFPA waveform design.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Rank Sum Nonparametric CFAR Detector in Nonhomogeneous Background
    • Authors: Xiangwei Meng;
      Pages: 397 - 403
      Abstract: The parametric CFAR detectors maintain a constant false alarm rate (CFAR) with an assumption of a known clutter distribution form. The representative ones of them are the cell-averaging (CA) CFAR, the greatest-of (GO) CFAR, and the ordered statistic (OS) CFAR, etc. In this work, we consider the rank sum (RS) nonparametric CFAR, which has an advantage that it can maintain CFAR even the distribution form of clutter becomes a different one. A closed form of the false alarm rate for the RS detector at clutter edges is derived, and a comparison of the performance of the RS detector in multiple targets situation and at clutter edges to that of the CA-CFAR, the GO-CFAR, and the OS-CFAR with noncoherent integration is made.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Decorrelation of Previously Communicated Information for an Interacting
           Multiple Model Filter
    • Authors: Duygu Acar;Umut Orguner;
      Pages: 404 - 422
      Abstract: In a sensor network compensation of the correlated information caused by previous communication is of utmost interest for distributed estimation. In this article, we investigate an information decorrelation approach that can be applied when using interacting multiple model filters in the sensor nodes for a family of jump Markov linear systems. Implementation issues that might arise while applying the decorrelation approach are addressed in detail. The investigated approach is compared with alternatives on simple distributed single maneuvering target tracking examples.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Antenna Selection for Target Tracking in Collocated MIMO Radar
    • Authors: Haowei Zhang;Junpeng Shi;Qiliang Zhang;Binfeng Zong;Junwei Xie;
      Pages: 423 - 436
      Abstract: How to utilize the limited antennas for tracking multiple targets plays a critical role in the collocated multiple-input multiple-output radar. A dynamic antenna selection strategy is proposed to address this problem. The basis of our strategy is to achieve the optimal antenna selection under the constraint of limited active antennas using the feedback information in the tracking recursion cycle, improving the worst case of estimate accuracy among multiple targets. Since the posterior Cramer–Rao lower bound quantifies the target tracking performance, it is derived and utilized as the optimization criterion. We then propose an efficient algorithm which integrates the convex relaxation technique with the local search to solve the problem. Simulation results show its superior performance compared with the random antenna selection strategy and the heuristic search algorithm. Moreover, the proposed strategy can provide the performance close to the exhaustive search method while maintaining reasonable runtime.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Measurement Extraction of Two Targets With Unequal and Unknown Intensities
           in an FPA
    • Authors: Andrew Finelli;Yaakov Bar-Shalom;Peter Willett;
      Pages: 437 - 447
      Abstract: This article extends previous work on location and intensity estimation for measurement extraction of targets in a focal plane array. Prior work has been done to extract single targets and two targets of equal intensity, whereas this work explores the case where two targets have unequal and unknown intensities. Here, we assume a Gaussian point spread function (PSF) with spread $sigma _{text{PSF}}$, but our approach could be applied to other PSF shapes. We present a maximum likelihood (ML) method for target extraction under resolved and unresolved assumptions. In the unresolved case, we estimate the parameters of a single target that represents the centroid of the two unresolved targets. We also present the Cramer–Rao lower bound (CRLB) of the estimation variances for both cases. Our simulation results show that resolved targets have their parameter vectors estimated efficiently (i.e., the variance meets the CRLB) when the targets are separated by $0.9sigma _{mathrm{PSF}}$, or about 1.8 pixel widths. We also find that estimation of the centroid parameters is efficient below a target separation of $0.65sigma _{{mathrm{PSF}}}$. Furthermore, we find that increased difference in the SNR of two targets causes the variances in the resolved scenario to be lower, and in the case of the unresolved scenario, to increase. We also derive and characterize a decision about target cardinality as a hypothesis testing problem, and develop a generalized likelihood ratio test to perform the decision making. The performance of this test is evaluated via Monte Carlo simulations, and matches well to theoretical predictions. Finally, we explore the effect of separation between targets, and individual target SNR on resolvability.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Maximum Likelihood and IRLS Based Moving Source Localization With
           Distributed Sensors
    • Authors: Xudong Zhang;Fangzhou Wang;Hongbin Li;Braham Himed;
      Pages: 448 - 461
      Abstract: In this article, we consider the problem of estimating the location and velocity of a moving source using a distributed passive radar sensor network. We first derive the maximum likelihood estimator (MLE) using direct sensor observations, when the source signal is unknown and modeled as a deterministic process. Since the MLE obtains the source location and velocity estimates through a search process over the parameter space and is quite computationally intensive, we also developed an efficient algorithm to solve the problem using a two-step approach. The first step finds the time difference of arrival (TDOA) and frequency difference of arrival (FDOA) estimates for each sensor with respect to a reference sensor by using a two-dimensional fast Fourier transform and interpolation, while the second step employs an iterative reweighted least square (IRLS) approach with a varying weighting matrix to determine the source location and velocity. To benchmark the performance of the proposed methods, a constrained Cramér–Rao bound (CRB) for the considered source localization problem is derived. Numerical results show that the IRLS approach has a lower signal-to-noise ratio threshold phenomenon compared with several recent TDOA/FDOA-based methods, especially when the source is considerably farther away from some sensors than others, creating a larger disparity in the quality of sensors observations.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Design of a Nonlinear Roll Mechanism for Airplanes Using Lie Brackets for
           High Alpha Operation
    • Authors: Ahmed M. Hassan;Haithem E. Taha;
      Pages: 462 - 475
      Abstract: A nonlinear controllability analysis for fixed-wing aircraft has been performed in an earlier effort by the authors, which revealed a novel roll mechanism due to a nonlinear interaction between elevator and aileron control inputs. In this effort, we perform a detailed investigation of this novel roll mechanism, called Lie Bracket Roll Augmentation (LIBRA). First, we show the nonlinear flight physics associated with the LIBRA mechanism. Second, using the Fliess functional expansion, we perform a theoretical study of the effectiveness (degree of controllability) of the LIBRA mechanism in comparison to the conventional mechanism (using ailerons only). Third, to simulate the airplane response to a LIBRA input, we cast the problem of executing the LIBRA mechanism as a nonholonomic motion planning problem. In such a problem, a Lie bracket input is applied to generate motion along an unactuated direction. A Lie bracket input represents a nonlinear interaction between two (or more) control inputs to steer the system along a direction that is not directly actuated by any of these inputs (or their linear combinations). In this language, the LIBRA mechanism is simply a Lie bracket interaction between the elevator and aileron control inputs. We modify existing nonholonomic motion planning algorithms for systems with drift to be more feasible for flight control applications with bounded controls. We show that the LIBRA novel roll mechanism is superior compared to the conventional one during stall, where the aileron sensitivity degrades. In particular, the novel roll mechanism can provide an order of magnitude enhancement in the rolling capability over the conventional roll mechanism near stall.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • On the Computation and Approximation of Outage Probability in Satellite
           Networks With Smart Gateway Diversity
    • Authors: Christos N. Efrem;Athanasios D. Panagopoulos;
      Pages: 476 - 484
      Abstract: The utilization of extremely high-frequency (EHF) bands can achieve very high throughput in satellite networks (SatNets). Nevertheless, the severe rain attenuation at EHF bands imposes strict limitations on the system availability. Smart gateway diversity (SGD) is considered indispensable in order to guarantee the required availability with reasonable cost. In this context, we examine a load-sharing SGD (LS-SGD) architecture, which has been recently proposed in the literature. For this diversity scheme, we define the system outage probability (SOP) using a rigorous probabilistic analysis based on the Poisson binomial distribution, and taking into consideration the traffic demand as well as the gateway (GW) capacity. Furthermore, we provide several methods for the exact and approximate calculation of SOP. As concerns the exact computation of SOP, a closed-form expression and an efficient algorithm based on a recursive formula are given, both with quadratic worst-case complexity in the number of GWs. Finally, the proposed approximation methods include well-known probability distributions (binomial, Poisson, normal) and a Chernoff bound. According to the numerical results, binomial and Poisson distributions are by far the most accurate approximation methods.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Infrared Target Detection in Cluttered Environments by Maximization of a
           
    • Authors: Bruce McIntosh;Shashanka Venkataramanan;Abhijit Mahalanobis;
      Pages: 485 - 496
      Abstract: Infrared target detection is a challenging computer vision problem which involves detecting small targets in heavily cluttered conditions while maintaining a low false alarm rate. We propose a network that optimizes a “target to clutter ratio”(TCR) metric defined as the ratio of the output energies produced by the network in response to targets and clutter. A TCR-network (TCRNet) is presented in which the filters of the first convolutional layer are composed of the eigenvectors most responsive to targets or to clutter. These vectors are analytically derived via a closed form optimization of the TCR metric. The remaining convolutional layers are trained using a novel cost function also designed to optimize the TCR criterion. We evaluate the performance of the TCRNet using a public domain medium wave infrared dataset released by the US Army's Night Vision Laboratories, and compare it to the state-of-the-art detectors such as Faster regions with convolutional neural networks (R-CNN) and Yolo-v3. The TCRNet demonstrates state-of-the-art results with greater than 30% improvement in probability of detection while reducing the false alarm rate by more than a factor of two when compared to these leading methods. Experimental results are shown for both day and night time images, and ablation studies are presented which demonstrate the contribution of the first layer eigenfilters, additional convolutional layers, and the benefit of the TCR cost function.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Compliant Force Sensor-Less Capture of an Object in Orbit
    • Authors: Angel Flores-Abad;Miguel A. García Terán;Israel U. Ponce;Manuel Nandayapa;
      Pages: 497 - 505
      Abstract: Space robots have been proposed to perform several tasks in orbit, such as repairing, refueling, and assembly. All those activities require the robot to interact with external objects in a safe and compliant form to avoid high impact forces that may damage the robot's components or the object to manipulate. Impedance controllers have demonstrated to be a suitable approach to perform similar tasks in ground. Therefore, implementing and analyzing impedance-based techniques in space is also worthy of study. Not only that, but also, methods that can reduce the number of components, weight and complexity should be considered. This article proposes the use of the disturbance observer for the design of an impedance controller to perform a safe capture of a target satellite by a space robot. First, the observer aids in the determination of the contact force between the servicer and the target. Later, once the almost perfect match between the actual and estimated contact force is demonstrated, the estimated force is used as input for an impedance controller with trajectory tracking. The advantages of estimating the contact force instead of measuring it are also discussed in the document. The design of the impedance control is performed such that the capturing process is compliant and safe, and, thus, it can help to advance toward an autonomous capture of space objects. A simulation experiment was set up to evaluate the performance of the proposed method. The results demonstrate that the contact force is bounded and behaves smoothly in a spring–mass–damper-like manner, imposing a stable contact between the robot's end effector and the servicer's capturing spot.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • A Hybrid Offline Optimization Method for Reconfiguration of Multi-UAV
           Formations
    • Authors: Bin Li;Jiangwei Zhang;Li Dai;Kok Lay Teo;Song Wang;
      Pages: 506 - 520
      Abstract: Formation reconfiguration of multiple unmanned aerial vehicles (UAVs) is a challenging problem. Mathematically, this problem is an optimal control problem subject to continuous state inequality constraints and terminal state equality constraints. The first challenge is that there are an infinite number of constraints to be satisfied for the continuous state inequality constraints, which makes the problem extremely difficult to be solved. The second challenge is that the control and state are usually both been discretized. This will result in noncontinuous control input. In addition, the discretized system may not always accurately approximate the original system. In this article, a hybrid offline optimization scheme is proposed to tackle these problems. Unlike the existing methods, the state variables are not required to be discretized and continuous control inputs can be obtained. In addition, the continuous state inequality constraints are tackled without increasing the total number of constraints. Simulation results show that the proposed hybrid optimization method outperforms the state-of-the-art method—the hybrid particle swarm optimization and genetic algorithm.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Comparison of Two Optimal Guidance Methods for the Long-Distance Orbital
           Pursuit-Evasion Game
    • Authors: Xin Zeng;Leping Yang;Yanwei Zhu;Fuyunxiang Yang;
      Pages: 521 - 539
      Abstract: The orbital pursuit-evasion game (OPE) is a topic of research that has been attracting increasing attention from scholars. However, most works based on the relative dynamics under a short-distance assumption is not applicable when the distance between two spacecrafts is too large. Accordingly, there should be two phases in the OPE, a long-distance OPE (LDOPE) as well as a short-distance one. This article concerns on the optimal guidance problem for the LDOPE. Two different models are introduced in this article to formulate the LDOPE, namely, the Cartesian model, and the spherical model. Then, to overcome the unacceptable solution computation time of traditional algorithms, such as the differential evolution (DE), a well-designed algorithm called “mixed global-local optimization strategy” (MGLOS), which consists of the global optimization phase, and the local optimization phase, is introduced in this article. The MGLOS is nearly two orders of magnitude more efficient than the DE. Moreover, simulations under different initial conditions demonstrate the robustness of the algorithm, and the accuracy, and efficiency of the Cartesian, and spherical models, respectively. Finally, the robustness of two models is analyzed by Monte Carlo simulation, which provides a quantified way to make a choice between two models depending on the measurement accuracy, and permitted maximum error.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Fault-Tolerant Finite-Time Controller for Attitude Tracking of Rigid
           Spacecraft Using Intermediate Quaternion
    • Authors: Daero Lee;
      Pages: 540 - 553
      Abstract: This article proposes a fault-tolerant finite-time controller for attitude tracking control of rigid spacecraft using intermediate quaternion in the presence of external disturbances, uncertain inertia parameter, and actuator faults. First, a novel nonsingular fast terminal sliding mode control law is derived using intermediate quaternion, free of singularity, ambiguity, and unwinding phenomenon. Second, a proposed controller is developed by combining the continuous nonsingular fast terminal sliding mode method with the finite-time disturbance observer. The key feature of the proposed control strategy is that it globally stabilizes the system in finite time, even in the presence of actuator faults, inertia uncertainty, and external disturbances. Simulation results are presented under actuator constraint to show the desirable properties and the superiority of the proposed controller compared to an asymptotic controller and nonsingular fast terminal sliding mode controller.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Long Coherent Integration in Passive Radar Systems Using Super-Resolution
           Sparse Bayesian Learning
    • Authors: Alexandra Filip-Dhaubhadel;Dmitriy Shutin;
      Pages: 554 - 572
      Abstract: Maximizing the coherent processing interval (CPI) is crucial when performing passive radar detection on weak signal reflections. In practice, however, the CPI is limited by the target movement. In this work, the extent of the range and Doppler migration effects occurring when using a long CPI to integrate the returns from an $L$-band digital aeronautical communication system (LDACS) based passive radar is studied. In particular, our simulations underline the extensive Doppler migration effect that arises even for nonaccelerating targets. To this end, the Keystone transform and fractional Fourier transform techniques are combined with the standard passive radar processing to enable the compensation of both range and Doppler migration effects. This nonmodel-based approach is, however, shown to have limitations, in particular for low signal-to-noise ratios and/or multitarget scenarios. To address these shortcomings, a novel model-based framework that allows to perform joint target detection and parameter estimation is developed. For this, a super-resolution sparse Bayesian learning approach is employed. This technique uses a multitarget observation model, which accurately accounts for the underlying range and Doppler migration effects and provides super-resolution estimation capabilities. This is particularly advantageous in the LDACS case since the narrow bandwidth generally limits the separation of closely spaced targets. The simulation experiments demonstrate the effectiveness of the algorithm and the advantages it provides when compared to the standard migration compensation approach.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Nested MIMO Radar: Coarrays, Tensor Modeling, and Angle Estimation
    • Authors: Junpeng Shi;Fangqing Wen;Tianpeng Liu;
      Pages: 573 - 585
      Abstract: This article addresses the problem of joint direction of departure (DOD) and direction of arrival (DOA) estimation with nested bistatic multiple input multiple output (MIMO) radar using tensor decomposition. We first employ the two-level nested transmit and receive arrays to develop the sum-difference coarray for constructing the Toeplitz and spatial smoothing matrices. We then generalize the three-way tensor model from DOD and DOA dimensions, and derive the optimized tensor by maximizing the number of detectable targets, where the existing COMFAC technique is exploited for angle estimation. We show that the proposed method can identify more targets and achieve better performance by enforcing the three-way structure information compared with the subspace-based algorithms. We also show that the conventional tensor model is just a special case. Finally, we derive the coarray Cramér–Rao Bound (CRB) for the nested MIMO radar, and also conduct a study for the conditions under which the CRB exists. Numerical simulations are provided to validate the theoretical analysis and demonstrate the performance improvement.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Attitude Coordination Control for Spacecraft With Disturbances and
           Event-Triggered Communication
    • Authors: Chenliang Wang;Lei Guo;Changyun Wen;Xiang Yu;Jian Huang;
      Pages: 586 - 596
      Abstract: In this article, a novel distributed attitude coordination control scheme is proposed for a group of rigid spacecraft with unknown disturbances. The communication topology is described by a general directed graph, and the leader's attitude is available to only a small fraction of followers. Different from existing attitude coordination control schemes, here an event-triggered communication strategy without Zeno phenomenon is designed, which avoids continuous communication between neighboring spacecraft and considerably reduces the communication burden. Moreover, a nonlinear observer is constructed for each follower, which enables us to estimate and compensate for a large class of disturbances exactly. The proposed scheme is able to ensure the boundedness of all closed-loop signals and steer the attitude tracking errors into an arbitrarily small residual set, regardless of the intermittent communication. Simulation results illustrate the effectiveness of the proposed scheme.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • GLRT-Based Adaptive Target Detection in FDA-MIMO Radar
    • Authors: Lan Lan;Angela Marino;Augusto Aubry;Antonio De Maio;Guisheng Liao;Jingwei Xu;Yuhong Zhang;
      Pages: 597 - 613
      Abstract: This article deals with the problem of adaptive target detection in the presence of homogeneous Gaussian interference with frequency diverse array multiple-input multiple-output radar. Adaptive detectors are devised according to the generalized likelihood ratio test criterion, where the position of the target within each range cell is assumed unknown. To obtain the maximum likelihood estimate of the target incremental range under the $H_1$ hypothesis, three different optimization strategies are pursued. They are, respectively, based on semidefinite programming, discrete grid search, and Newton method. At the analysis stage, a detection performance comparison is carried on among the new proposed adaptive detectors, benchmark, and mismatched receivers. Numerical results corroborate the effectiveness of the developed receivers.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Design and Implementation of High Reliability Electrical Power System for
           2U NutSat
    • Authors: Yu-Kai Chen;Yi-Chen Lai;Wen-Chi Lu;Albert Lin;
      Pages: 614 - 622
      Abstract: This article proposes the design and implementation of an electrical power system (EPS) for 2U CubeSat using a single-ended primary-inductor converter (SEPIC) along with the perturbed and observe method for the maximum power point tracking (MPPT). SEPIC converters have the advantages of input current continuity, voltage boosting and bucking, short-circuit protection, low-side driver, and noninverted input and output voltages. When the battery voltage is too low, by adding a low power consumption latching relay to develop a novel topology, the battery can be directly charged with solar panels without the MPPT algorithm and to improve the system reliability. In addition to the on-board computer subsystem, we can independently control whether to turn on the power according to the battery capacity and importance priority for each subsystem of CubeSat. The satellite is operated in outer space that the environment is wide temperature variation, vacuum, and high electromagnetic radiation. Therefore, the satellite was subjected to various types of tests, such as vacuum, thermal cycling, and radiation tests, to verify the system's capacity for enduring the aforementioned environmental changes. Finally, implementations and various tests were carried out to verify the viability and the accuracy, and reliability of the EPS of the satellite.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • A Distributed MIMO Radar With Joint Optimal Transmit and Receive Signal
           Combining
    • Authors: Satya Ganesh Dontamsetti;Ratnam V. Raja Kumar;
      Pages: 623 - 635
      Abstract: Multiple-input multiple-output (MIMO) radar systems are popular for their ability to mitigate the target radar cross section fluctuations and null Doppler. However, MIMO radar fundamentally suffers from a notable signal-to-noise ratio (SNR) loss compared to an ideal phased-array (PA) radar. In order to overcome this drawback, a distributed MIMO radar scheme with joint optimal transmit and receive signal combining method is proposed in this work. In view of the optimality, the proposed scheme outperforms the most popular combining methods of MIMO radar addressed in the literature. Also, the proposed scheme performs same as the ideal PA radar in case of the nonfluctuating target. In case of fluctuating targets, the proposed scheme outperforms PA radar at high SNR.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • An RCB-Like Steering Vector Estimation Method Based on Interference Matrix
           Reduction
    • Authors: Pan Zhang;Zhiwei Yang;Guisheng Liao;Gang Jing;Teng Ma;
      Pages: 636 - 646
      Abstract: To develop an adaptive beamformer against the signal of interest (SOI) steering vector mismatch, a robust Capon beamformer (RCB) like steering vector estimation method based on the interference matrix reduction is proposed. Different from the RCB and its modified versions that optimize the SOI steering vector with the Capon power estimator, this article designs an SOI power estimator to formulate the steering vector optimization problem with an uncertainty set constraint. In terms of that, the unknown SOI covariance matrix is needed to realize the SOI power estimator, an efficient interference matrix reconstruction way via SOI blocking and matrix eigen-transition is exploited to reduce the interference component from the sample covariance matrix. Herein, after solving the given steering vector optimization problem and adding the noise component to the aforesaid interference matrix, the weight vector of the derived algorithm is, thereby, computed using the estimated SOI steering vector and interference covariance matrix. The proposed method only requires the source number and prior direction of the SOI. The numerical simulations show that the proposed approach can outperform the compared ones with reduced complexity in the situation of various steering vector mismatches.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Nonlinear Filtering With a Polynomial Series of Gaussian Random Variables
    • Authors: Simone Servadio;Renato Zanetti;Brandon A. Jones;
      Pages: 647 - 658
      Abstract: Filters relying on the Gaussian approximation typically incorporate the measurement linearly, i.e., the value of the measurement is premultiplied by a matrix-valued gain in the state update. Nonlinear filters that relax the Gaussian assumption, on the other hand, typically approximate the distribution of the state with a finite sum of point masses or Gaussian distributions. In this work, the distribution of the state is approximated by a polynomial transformation of a Gaussian distribution, allowing for all moments, central and raw, to be rapidly computed in a closed form. Knowledge of the higher order moments is then employed to perform a polynomial measurement update, i.e., the value of the measurement enters the update function as a polynomial of arbitrary order. A filter employing a Gaussian approximation with linear update is, therefore, a special case of the proposed algorithm when both the order of the series and the order of the update are set to one: it reduces to the extended Kalman filter. At the cost of more computations, the new methodology guarantees performance better than the linear/Gaussian approach for nonlinear systems. This work employs monomial basis functions and Taylor series, developed in the differential algebra framework, but it is readily extendable to an orthogonal polynomial basis.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Explainability of Deep SAR ATR Through Feature Analysis
    • Authors: Carole Belloni;Alessio Balleri;Nabil Aouf;Jean-Marc Le Caillec;Thomas Merlet;
      Pages: 659 - 673
      Abstract: Understanding the decision-making process of deep learning networks is a key challenge that has rarely been investigated for synthetic aperture radar (SAR) images. In this article, a set of new analytical tools is proposed and applied to a convolutional neural network (CNN) handling automatic target recognition on two SAR datasets containing military targets. First, an analysis of the respective influence of target, shadow, and background areas on classification performance is carried out. The shadow appears to be the least used portion of the image affecting the decision process, compared to the target and clutter, respectively. Second, the location of the most influential features is determined with classification maps obtained by systematically hiding specific target parts and registering the associated classification rate relative to the images to be classified. The location of the image areas without which classification fails is target type and orientation specific. Nonetheless, a strong contribution of specific parts of the target, such as the target top and the areas facing the radar, is noticed. Finally, results show that features are increasingly activated along the CNN depth according to the target type and its orientation, even though target orientation is absent from the loss function.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Reexamining Low-Latitude Ionospheric Error Bounds: An SBAS Approach for
           Brazil
    • Authors: Leonardo Marini-Pereira;Sam P. Pullen;Alison de Oliveira Moraes;
      Pages: 674 - 689
      Abstract: The ionosphere in low-latitude regions is a major challenge for a satellite-based augmentation system (SBAS). The intense dynamics of this layer of the atmosphere in this part of the globe is one of the main reasons why Brazil discarded years ago the idea of deploying its own SBAS. In this article, we re-examine the ionospheric error bounds for a high-density ground station network in Brazil by updating previous work that assessed specific parameters for low latitudes, especially the ones related to the generation of the ionospheric error bounds expressed by the grid ionospheric vertical error (GIVE). Ionospheric delay maps and their respective GIVE values were generated by varying the functional model used in the interpolation of the grid points and the decorrelation parameter of the measurements for quiet and active days of the ionosphere. The resulting GIVE maps show values significantly higher than the bounds found in mid-latitudes and represent one of the main contributions of this article. An availability assessment for APV-I shows that the planar fit model with a spatial decorrelation standard deviation of 1 m provides the best availability for quiet days, while a quadratic fit with a decorrelation parameter of 2 m results in better availability for active days. Even though it would be possible to provide some service in quiet days within the area with a higher density of reference stations, the resulting availability is not ideal for a real SBAS when the ionosphere is more active.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Evaluation of Real-Time Predictive Spectrum Sharing for Cognitive Radar
    • Authors: Jacob A. Kovarskiy;Benjamin H. Kirk;Anthony F. Martone;Ram M. Narayanan;Kelly D. Sherbondy;
      Pages: 690 - 705
      Abstract: The growing demand for radio frequency (RF) spectrum access poses new challenges for next-generation radar systems. To operate in a crowded electromagnetic environment, radars must coexist with other RF emitters while maintaining system performance. This work evaluates the performance of a spectrum sharing cognitive radar system, which predicts and avoids RF interference (RFI) in real time. The system applies a cognitive perception-action cycle that senses RFI, learns RFI behavior over time, and adapts the radar's frequency band of operation. Through cognition, the system learns a stochastic model describing RF activity. This model allows the cognitive radar to predict RF activity in real time and share the spectrum with emitters, such as communication systems. A set of synthetic and measured interference signals are used to evaluate the performance of this predictive spectrum sharing scheme. This work assesses the impact of RFI on the cognitive radar's range profile with respect to variation in RF environment. The system demonstrates accurate avoidance of deterministic RFI with a degradation in spectrum sharing efficiency as variability over time increases.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Dynamic Discrete Pigeon-Inspired Optimization for Multi-UAV Cooperative
           Search-Attack Mission Planning
    • Authors: Haibin Duan;Jianxia Zhao;Yimin Deng;Yuhui Shi;Xilun Ding;
      Pages: 706 - 720
      Abstract: For multiple unmanned aerial vehicles (UAVs) performing aerial search-attack tasks, there is a tradeoff between maximizing total benefit and minimizing consumption under the validity of constraints. This article proposes a dynamic discrete pigeon-inspired optimization algorithm to handle cooperative search-attack mission planning for UAVs, which integrates the centralized task assignment and distributed path generation aspects of the problem. Besides, a solution acceptance strategy is proposed to avoid frequent task switching. To design a reasonable objective function, the probability map is constructed and updated by Bayes formula to guide the following search motion, and a response threshold sigmoid model is adopted for target allocation during executing attack. Moreover, the flyable trajectories are generated by B-spline curves based on the simplified waypoints. Finally, numerical experiments prove that the proposed methods can provide feasible solutions for multiple UAVs considering different scenarios, such as the absence or presence of threats and insufficient resources. The results also show that the solution acceptance strategy is effective to improve performance. Moreover, the extensible mission planning system also integrates with an interactive 3D visualization simulation module, where the multi-UAV coordinated flight processes are demonstrated dynamically.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Trigonometric Series-Based Smooth Flight Trajectory Generation
    • Authors: Haichao Hong;Patrick Piprek;Rubens Junqueira Magalhães Afonso;Florian Holzapfel;
      Pages: 721 - 728
      Abstract: In practical scenarios, flight trajectories shall be smooth to comply with the required curvature behavior. This article describes a trajectory generation method that is able to produce smooth control commands with an arbitrary order of smoothness. The system inputs are formulated analytically as trigonometric series in which the coefficients are to be determined by optimization. Effective implementations of the proposed method are presented. These include a numerical benchmark that shows how the order of the series shapes the results as well as the comparison with the optimal solution, and the unmanned aerial vehicle transition trajectory generation using a convex optimization framework integrated with the proposed design.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Fault-Tolerant Attitude Stabilization for Spacecraft With Low-Frequency
           Actuator Updates: An Integral-Type Event-Triggered Approach
    • Authors: Chengxi Zhang;Ming-Zhe Dai;Peng Dong;Henry Leung;Jihe Wang;
      Pages: 729 - 737
      Abstract: This article investigates the attitude stabilization control problem with low-frequency communication to actuators in the framework of sampled-data control. A novel event-triggered sampling control policy is proposed by employing an integral-type triggering function where the determination of all sampling times is by judging the properties of this function including the integration of measurement errors. Using the Lyapunov-based approach, we show that the stability of the closed-loop system can be guaranteed in the presence of external disturbance, inertia uncertainty, and actuator fault. Compared with conventional attitude control policies, the proposed algorithm significantly reduces the data-rate requirement in updating the actuator while providing high reliability and accurate performance for attitude stabilization. Compared with the traditional event-triggered sampling, the proposed policy is no longer by judging the instantaneous state of measurement errors, which reduces the sampling frequency and does not increase the computational burden. Numerical simulations are conducted to show a decent performance of the algorithm.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Golay Pairs Having Larger Swap Sets
    • Authors: Gregory E. Coxson;
      Pages: 738 - 743
      Abstract: Binary Golay pairs are examined with an interest in finding examples, in which members of the pair can be replaced with other codes sharing the same autocorrelation, but not due to negation and reversal. These are referred to as shared-autocorrelation (or shared-$rm ACS$) Golay pairs. Golay pairs can always formed from other Golay pairs by reversing and/or negating codes in those pairs; the discovery of other possibilities offers the promise of enhanced unpredictability by waveform diversity. A 1998 paper by Djokovic, which lists such pairs at lengths 32 and 40, is used as evidence that such pairs not only exist, but also likely exist in significant numbers. A common structure in these codes is determined, and conditions found for half-codes that can be employed to form larger examples. Furthermore, a necessary condition is found for code lengths allowing these shared-$rm ACS$ Golay pairs.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • Efficient Sensing for Compressive Estimation of Frequency of a Real
           Sinusoid
    • Authors: Hui Cao;Yiu Tong Chan;Hing Cheung So;
      Pages: 744 - 750
      Abstract: Linear least squares (LS) frequency estimators are popular because they are closed form and easy to implement. However, they are applicable to compressive frequency estimation only after reconstruction. This is because compressive sensing (CS) breaks up the temporal order of the original sinusoidal samples. This correspondence proposes an efficient sensing scheme to obtain CS samples. They are sums of the Nyquist rate samples of the signal. There is no need for matrix multiplications and the random modulator preintegrator. A modified LS estimator is able to estimate frequency directly from the CS samples without reconstruction. This estimator has accuracy that matches the theoretical lower bound, as shown by two examples.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
  • DecaWave Ultra-Wideband Warm-Up Error Correction
    • Authors: Juri Sidorenko;Volker Schatz;Norbert Scherer-Negenborn;Michael Arens;Urs Hugentobler;
      Pages: 751 - 760
      Abstract: In the field of indoor localization, ultra-wideband (UWB) technology is no longer dispensable. The market demands that the UWB hardware has to be cheap, precise, and accurate. These requirements lead to the popularity of the DecaWave UWB system. The great majority of the publications about this system deal with the correction of the signal power, hardware delay, or clock drift. It has traditionally been assumed that this error only appears at the beginning of the operation and is caused by the warm-up process of the crystal. In this article, we show that the warm-up error is influenced by the same error source as the signal power. To our knowledge, no scientific publication has explicitly examined the warm-up error before. This work aims to close this gap and, moreover, to present a solution, which does not require any external measuring equipment and only has to be carried out once. It is shown that the empirically obtained warm-up correction curve increases the accuracy for the two-way ranging significantly.
      PubDate: Feb. 2021
      Issue No: Vol. 57, No. 1 (2021)
       
 
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