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Journal Cover Aerospace and Electronic Systems, IEEE Transactions on
  [SJR: 1.151]   [H-I: 103]   [237 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0018-9251
   Published by IEEE Homepage  [191 journals]
  • IEEE Aerospace and Electronic Systems Society
    • Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • PUMA: An Improved Realization of MODE for DOA Estimation
    • Authors: Cheng Qian;Lei Huang;Mingyang Cao;Junhao Xie;Hing Cheung So;
      Pages: 2128 - 2139
      Abstract: The method of direction estimation (MODE) offers appealing advantages such as asymptotic efficiency with mild computational complexity and excellent performance in handling coherent signals, which are not shared by conventional subspace-based methods. However, the MODE employs additional assumption and constraints on the symmetry of the root polynomial coefficients, which might cause severe performance degradation in the scenario of low signal-to-noise ratio/small sample size, since any estimation error will be enlarged twice due to the symmetry. Moreover, the standard realization for MODE does not have a closed-form solution for updating its estimates. In this paper, the optimization problem of MODE is proved to be equivalent to that of the principal-eigenvector utiliztion for modal analysis (PUMA) algorithm. We show that PUMA which has closed-form solution, that does not rely on any additional assumption and constraint on the coefficients, is a better surrogate than MODE for minimizing the same cost function. Extensive simulation results are carried out to support our standpoint.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • A Robust Translational Motion Compensation Method for ISAR Imaging Based
           on Keystone Transform and Fractional Fourier Transform Under Low SNR
           Environment
    • Authors: Dong Li;Muyang Zhan;Hongqing Liu;Yong Liao;Guisheng Liao;
      Pages: 2140 - 2156
      Abstract: In this work, a parametric-based approach is proposed to perform joint range alignment and phase adjustment based on the intention of fully exploiting the energy of all the scatterers in the moving target and the two-dimensional coherent accumulation gain of both range and azimuth compressions. To that end, first, translational motion is modeled as a polynomial signal, and inspired by the fact that all the scatterers in the moving target experience the same translational range history, the phase difference operation and keystone transform (KT) are utilized to transform the energy of all the scatterers into one range cell. Second, by the virtue of the fractional Fourier transform (FrFT), the energy of all the scatterers is coherently accumulated into a peak point, and from which the polynomial coefficients can be obtained accurately. With the estimated polynomial coefficients, the dechirp operation and KT are applied jointly to compensate range misalignment and phase error. The analysis of the proposed method shows that it is of low computational complexity due to avoiding multidimensional search and improves the output SNR providing satisfactory low SNR performance. The experimental results are provided to demonstrate the performance of the proposed method compared with the state-of-the-art algorithms.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • New Electrical Power Supply System for All-Electric Propulsion Spacecraft
    • Authors: Ming Fu;Donglai Zhang;Tiecai Li;
      Pages: 2157 - 2166
      Abstract: This paper proposes a novel electrical power supply system architecture (power conditioning and processing unit, PCPU) for high-power all-electric propulsion spacecraft platform with high-voltage power bus (HVBUS) powering thrusters and regulated power bus (VBUS) powering onboard payloads, respectively. The design principle of function modules in PCPU has been analyzed. Besides, the test on electrical characteristic of VBUS and HVBUS in prototyped system proves the stable and reliable work of buses in PCPU.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • PI and PWM Sliding Mode Control of POESLL Converter
    • Authors: Hadi Nasiri Jazi;Alireza Goudarzian;Rohallah Pourbagher;Sayed Yaser Derakhshandeh;
      Pages: 2167 - 2177
      Abstract: The positive output elementary superlift-Luo converter (POESLLC) is a type of dc/dc converter. This dc/dc converter has an attractive advantage of a high voltage transfer gain as compared with other conventional dc/dc converters. Because of the voltage and load variations and also switching operation, the dynamic and static performances of the POESLLC are nonlinear and time varying. In order to achieve an excellent performance, a nonlinear controller is required. In this paper, a robust and fast response controller for voltage regulation of a POESLLC is presented. A proportional integral and pulse width modulation sliding mode controller are combined to control a third-order POESLLC. The proposed controller can be applied in the continuous conduction mode. Some simulations and experimental results are presented to show the effectiveness of the developed controller in different operating conditions. Furthermore, it will be shown that the developed controller is successful in suppressing the steady-state error of the output voltage of the POESLLC as well as the number of reduction of sensors.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Transmit Signal Design in Colocated MIMO Radar Without Covariance Matrix
           Optimization
    • Authors: Sadjad Imani;Mohammad Mahdi Nayebi;Seyed Ali Ghorashi;
      Pages: 2178 - 2186
      Abstract: In this paper, the problem of the waveform design for colocated multiple-input multiple-output (MIMO) radars is considered in two parts. In the first part, we design transmit waveform in order to approximate the desired beampattern with low number of samples in the transmitter. Unlike the traditional waveform design methods, in our solution, waveforms are designed for a specific number of samples. Also, the constant envelope constraint that is an important practical constraint is considered. In the second part, we jointly design the transmit waveform and receive filter by a sequential algorithm, considering a priori information of target and interference angle locations. We have evaluated the performance of the proposed algorithms via numerical simulations and shown that the proposed algorithm in the first part is able to approximate the desired beampattern with low number of samples. Also, our method in the second part achieves better signal-to-interference-plus-noise ratio performance compared with the existing active sensing array methods (e.g., phased-array and correlated MIMO radars).
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • High-Resolution Spaceborne SAR Processing Using the Decomposed Transfer
           Function
    • Authors: Knut Eldhuset;
      Pages: 2187 - 2198
      Abstract: In this paper, a new analytic decomposed transfer function (DTF) for spaceborne synthetic aperture radar processing is calculated using the stationary phase approximation and Taylor's series expansion. The DTF copes with large Doppler centroid variations and executes range cell migration correction, secondary range compression, azimuth compression, and higher order effects. A fourth-order (DTF4) and fifth-order (DTF5) algorithms have been implemented using segmented block processing. It is shown that the DTF4 yields high quality 3-look target responses at azimuth resolution 0.3 m and range resolution 0.5 m at low squint (yaw = 0.3°) for X-band. At higher squint (yaw = 7.5°) the DTF5 has to be used to obtain adequate image quality.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Two-Step Sequential Detection in Agile-Beam Radars: Performance and
           Tradeoffs
    • Authors: Emanuele Grossi;Marco Lops;Luca Venturino;
      Pages: 2199 - 2213
      Abstract: In this paper, we consider a surveillance radar equipped with an electronically scanned antenna and study the performance of a two-step sequential detection procedure, where, for each resolution cell, a second observation is taken if a reliable decision cannot be made after the first one. At the design stage, we optimize the available degrees of freedom (namely, dwell time and detection thresholds) so as to maximize the detection rate (DR), defined as the average number of detections from a target per unit of time, under a constraint on the false alarm rate (FAR), which is the average number of false alarms per unit of time from the inspected area. This is motived by the fact that DR and FAR, beside of being per se meaningful figures of merit for parameter tuning, allow a fair performance comparison among detection strategies with different scanning policies. Examples are presented to illustrate the effects of this design philosophy under the two relevant situations of a slowly fluctuating and a fast-fluctuating target response, also in the presence of clutter.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • SAR Ground Plane Mover Signatures for Nonzero Radar Ascent
    • Authors: David Alan Garren;
      Pages: 2214 - 2220
      Abstract: Recent spotlight synthetic aperture radar analyses predict the two-dimensional range migration signature smears induced by targets with arbitrary motion in the ground plane. These investigations were limited to a constant-velocity radar motion with level flight path. The current correspondence removes this constraint by including the radar trajectory ascent angle.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • A New Three-Dimensional Sliding Mode Guidance Law Variation With Finite
           Time Convergence
    • Authors: Hyo-Sang Shin;Antonios Tsourdos;Ke-Bo Li;
      Pages: 2221 - 2232
      Abstract: This paper develops a new three-dimensional (3-D) guidance law which guarantees the interception of manoeuvring targets in a finite time. The new guidance law accepts the concept that nullifying the line-of-sight rate guarantees the interception of the target and its derivation is based on finite time sliding mode guidance. By using a 3-D kinematic equation set constructed in a rotating coordinate system, the proposed guidance law alleviates an issue of general 3-D guidance caused by the cross coupling effect between pitch and yaw planes. In theoretical analysis, finite time convergence of the new guidance law is proved and compared with that of a practical sliding mode guidance law. Characteristics such as energy consumption and convergence boundary layer are also theoretically analyzed. Simulation results demonstrate that the new guidance law effectively intercepts manoeuvring targets in a finite time and analysis results are valid.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Image Matting for Automatic Target Recognition
    • Authors: Hyun-Woong Cho;Young-Rae Cho;Woo-Jin Song;Byoung-Kwang Kim;
      Pages: 2233 - 2250
      Abstract: Features used in the classification of targets are generally based on the shape or gray-level information of the preprocessed target chip. Consequently, the performance of an automatic target recognition (ATR) system critically depends on the preprocessing result. In this paper, we propose to apply recent advances in image matting to address these challenges. First, a trimap is automatically generated in an adaptive manner to assign appropriate known foreground and background constraints. Then modified geometric clustering, which estimates the target center robustly, is performed on the estimated trimap. Then propagation-based matting is used to remove nontarget regions while retaining target information. The proposed framework is evaluated using visual examination, ATR performance comparison, and constraints dependency analysis. Our method has robust capabilities and outperforms conventional schemes.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Kalman-Gain Aided Particle PHD Filter for Multitarget Tracking
    • Authors: Abdullahi Daniyan;Yu Gong;Sangarapillai Lambotharan;Pengming Feng;Jonathon Chambers;
      Pages: 2251 - 2265
      Abstract: We propose an efficient sequential Monte Carlo probability hypothesis density (PHD) filter which employs the Kalman-gain approach during weight update to correct predicted particle states by minimizing the mean square error between the estimated measurement and the actual measurement received at a given time in order to arrive at a more accurate posterior. This technique identifies and selects those particles belonging to a particular target from a given PHD for state correction during weight computation. Besides the improved tracking accuracy, fewer particles are required in the proposed approach. Simulation results confirm the improved tracking performance when evaluated with different measures.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Analysis of Path-Length Effects in Multiloop Cross-Eye Jamming
    • Authors: Warren Paul du Plessis;
      Pages: 2266 - 2276
      Abstract: The effect of path-length differences on multiloop retrodirective cross-eye jammers is evaluated. It is shown that such jammers may act as beacons, and the conditions under which this occurs are investigated for two-loop jammers. The sensitivity of the two-loop cross-eye gain to path-length differences is also studied and is found to be small for small path-length differences, but to increase rapidly. The effect of the two-loop cross-eye jammer parameters on path-length effects is also considered.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Adaptive Dynamic Surface Control for a Hypersonic Aircraft Using Neural
           Networks
    • Authors: Jongho Shin;
      Pages: 2277 - 2289
      Abstract: A hypersonic aircraft dynamic model is highly nonlinear because its flight conditions are usually determined at high altitude and Mach number. Therefore, there always exist differences between the dynamical model and real system, and uncertainties during the flight, thus, leading significant degradation of control performance. To solve the performance degradation problem, this paper proposes neural networks-based adaptive velocity and altitude tracking controllers. In order for that, the hypersonic aircraft model is transformed into an uncertain feedback system, which has both matched and unmatched uncertainties, by differentiating the velocity and altitude with respect to time. Then, the overall tracking control system is designed systematically by introducing virtual control inputs and dynamic surface control. During the design process, an inverse of an input gain matrix is directly trained and adapted to remove the matched uncertainty and controller singularity problem simultaneously. In addition, several adaptive elements with saturation functions are added to handle all the matched and unmatched uncertainties. The proposed controller guarantees the uniformly ultimate boundedness of the tracking error by utilizing deadzoned errors. Finally, numerical simulations with the uncertain hypersonic aircraft are performed to demonstrate the effectiveness of the proposed approach.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Impedance-Dependent Wideband Digital Predistortion of Solid-State Radar
           Amplifiers
    • Authors: Zachary Dunn;Mark Yeary;Caleb Fulton;Rafael Rincon;
      Pages: 2290 - 2303
      Abstract: Spectral regrowth and waveform distortion caused by wideband signals input into active phased array antenna systems is the problem this paper addresses. The paper's unique contribution is the development of the impedance-dependent memory polynomial model, capable of solving nonlinear predistortion model parameters for a solid-state high power amplifier with varying load impedance resulting from active electronic beamsteering. Wideband load impedance mismatched tests demonstrate the effectiveness of this technique on a 2.7 GHz, 8 W amplifier.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Accuracy of Range-Based Cooperative Positioning: A Lower Bound Analysis
    • Authors: Liang Heng;Grace Xingxin Gao;
      Pages: 2304 - 2316
      Abstract: Accurate location information is essential for mobile systems such as wireless sensor networks. A location-aware sensor network generally includes two types of nodes: Sensors whose locations to be determined and anchors whose locations are known a priori. For range-based cooperative positioning, sensors' locations are deduced from anchor-to-sensor and sensor-to-sensor range measurements. Positioning accuracy depends on the network parameters such as network connectivity and size. This paper provides a generalized theory that quantitatively characterizes such a relation between network parameters and positioning accuracy. We use the average degree as a connectivity metric and use geometric dilution of precision (DOP) to quantify positioning accuracy. Under the assumption that nodes are randomly deployed, we prove a novel lower bound on expectation of average geometric DOP (LB-E-AGDOP) and derives a closed-form formula that relates LB-E-AGDOP to only three parameters: Average anchor degree, average sensor degree, and number of sensor nodes. The formula shows that positioning accuracy is approximately inversely proportional to the average degree, and a higher ratio of average anchor degree to average sensor degree yields better positioning accuracy. Furthermore, the paper shows a strong connection between LB-E-AGDOP and the best achievable accuracy. Finally, we demonstrate the theory via numerical simulations with three different random graph models.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Adaptive Auxiliary Particle Filter for Track-Before-Detect With Multiple
           Targets
    • Authors: Luis Úbeda-Medina;Ángel F. García-Fernández;Jesús Grajal;
      Pages: 2317 - 2330
      Abstract: A novel particle filter for multiple target tracking with track-before-detect measurement models is proposed. Particle filters efficiently perform target tracking under nonlinear or non-Gaussian models. However, their application to multiple target tracking suffers from the curse of dimensionality. We introduce an efficient particle filter for multiple target tracking which deals with the curse of dimensionality better than previously developed methods. The proposed algorithm is tested and compared to other multiple target tracking particle filters.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • The Multidimensional Cramér–Rao–Leibniz Lower Bound for Likelihood
           Functions With Parameter-Dependent Support
    • Authors: Qin Lu;Yaakov Bar-Shalom;Peter Willett;Francesco Palmieri;Fred Daum;
      Pages: 2331 - 2343
      Abstract: One regularity condition for the classical Cramér-Rao lower bound (CRLB) of an unbiased estimator to hold-that the support of the likelihood function (LF) should be independent of the parameter to be estimated-has recently been relaxed to the case of parameter-dependent support as long as the LF is continuous at the boundary of its support. For the case where the LF is not continuous on the boundary of its support, a new modified CRLB-designated the Cramér-Rao-Leibniz lower bound (CRLLB) as it relies on the Leibniz integral rule-has also been presented for the scalar parameter case. The present work derives the multidimensional CRLLB for the case of LF with parameter-dependent support by applying the general Leibniz integral rule to complete the framework of the CRLLB.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Capacity Statistics Evaluation for Next Generation Broadband MEO Satellite
           Systems
    • Authors: Charilaos I. Kourogiorgas;Nikolaos Lyras;Athanasios D. Panagopoulos;Daniele Tarchi;Alessandro Vanelli-Coralli;Alessandro Ugolini;Giulio Colavolpe;Pantelis-Daniel Arapoglou;
      Pages: 2344 - 2358
      Abstract: In this paper, the performance of a reference medium earth orbit (MEO) satellite constellation system operating at Ka-band and employing single links to ground is compared with next generation advanced systems in higher RF or optical bands employing multiple diversity links. The fill rate of existing MEO constellations offering broadband and trunking services in Ka-band is growing fast, rendering the search for additional spectrum of vital importance. Therefore, this paper reports on the results of a system study investigating the option of using Q/V-band, or even optical wavelengths, instead of Ka-band, to deliver substantially higher system capacity. The system study takes a holistic approach covering from atmospheric channel impairments to waveform optimization and system analysis for realistic assumptions. After proposing a sophisticated channel model to generate spatio-temporal time series of atmospheric attenuation, an optimization of the performance at physical layer is performed to derive the inputs necessary to the system analysis. Five different advanced high frequency RF and optical systems are compared in terms of outage capacity and availability for various locations of single ground stations, multiple ground stations (site diversity) and from multiple satellites (orbital diversity). For maximizing the realism of the comparison, similar on board satellite resources (mass, power) are assumed for all scenarios.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Visual-INS Using a Human Operator and Converted Measurements
    • Authors: Meir Pachter;Turner J. Montgomery;
      Pages: 2359 - 2371
      Abstract: A method for intermittently aiding an inertial navigation system (INS) is explored in which a ground feature of unknown position is optically tracked over a short measurement epoch-one then refers to Visual-INS. In contrast to current machine vision-based research trends, a human operator is entrusted with visually tracking the ground feature. Converted measurements of the feature position are generated from successive bearing measurements, and the estimated aircraft position. A linear regression algorithm is then applied to the converted measurements providing an estimate of the INS horizontal velocity components' errors and also accelerometer biases. At the completion of the measurement epoch, the INS is corrected by subtracting out the estimated velocity errors and using the estimated accelerometer biases. Aiding the INS in this manner provides a significant improvement in the accuracy of the INS-provided aircraft navigation state estimates when compared to those of a free/unaided INS. Applications for this autonomous navigation method include navigation in global positioning system denied environments and/or when the use of RF transmitting navigation aids is undesirable.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Regularized Difference Criterion for Computing Discriminants for
           Dimensionality Reduction
    • Authors: Alex J. Aved;Erik P. Blasch;Jing Peng;
      Pages: 2372 - 2384
      Abstract: Hyperspectral data classification has shown potential in many applications. However, a large number of spectral bands cause overfitting. Methods for reducing spectral bands, e.g., linear discriminant analysis, require matrix inversion. We propose a semidefinite programming for linear discriminants regularized difference (SLRD) criterion approach that does not require matrix inversion. The paper establishes a classification error bound and provides experimental results with ten methods over six hyperspectral datasets demonstrating the efficacy of the proposed SLRD technique.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • An Interactive Fuzzy Physical Programming for Solving Multiobjective Skip
           Entry Problem
    • Authors: Runqi Chai;Al Savvaris;Antonios Tsourdos;Yuanqing Xia;
      Pages: 2385 - 2398
      Abstract: The multicriteria trajectory planning for space manoeuvre vehicle (SMV) is recognized as a challenging problem. Because of the nonlinearity and uncertainty in the dynamic model and even the objectives, it is hard for decision makers to balance all of the preference indices without violating strict path and box constraints. In this paper, to provide the designer an effective method and solve the trajectory hopping problem, an interactive fuzzy physical programming algorithm is introduced. A new multiobjective SMV optimal control problem is formulated and parameterized using an adaptive technique. By using the density function, the oscillations of the trajectory can be captured effectively. In addition, an interactive decision-making strategy is applied to modify the current designer's preferences during optimization process. Two realistic decision-making scenarios are conducted by using the proposed algorithm; Simulation results indicated that without driving objective functions out of the tolerable region, the proposed approach can have better performance in terms of the satisfactory degree compared with other approaches like traditional weighted-sum method, goal programming and fuzzy goal programming. Also, the results can satisfy the current preferences given by the decision makers. Therefore, the method is potentially feasible for solving multicriteria SMV trajectory planning problems.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Robust LFM Target Detection in Wideband Sonar Systems
    • Authors: Dong-Hun Lee;Jong-Woo Shin;Dae-Won Do;Sang-Moon Choi;Hyoung-Nam Kim;
      Pages: 2399 - 2412
      Abstract: Linear frequency modulation (LFM) signals have been widely used for target detection in active sonar systems due to their robustness to reverberation. However, LFM active sonar requires a large number of reference signals for detecting targets moving with unknown speeds. To obtain more accurate detection results, more reference signals are required, resulting in an increased computational burden and memory size. To cope up with this problem, we propose a new fast target detection method that is robust to the variation of unknown target speed. A large number of reference signals come into a single reference signal by aligning them with precalculated time-shifts, which is followed by a summation process. Both narrowband and wideband cases are considered. The proposed method secures a signal-to-noise ratio (SNR), approaching that of the optimal matched filter output, that is also robust to the variation of target speed and thus it is very useful for the practical use in antitorpedo torpedoes or supercavitating underwater missiles that need to equip low-complexity and robust signal processing systems. Moreover, a rough Doppler estimation is presented using the proposed replica design method. Performance analyses show that the proposed method provides output SNR close to the optimal performance and that the computational load is extremely reduced as compared to the conventional LFM target detection method.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Optimal Aircraft Planar Navigation in Static Threat Environments
    • Authors: Andrey V. Savkin;Hailong Huang;
      Pages: 2413 - 2426
      Abstract: We consider the problem of navigating a military aircraft in a threat environment to its final destination while minimizing the maximum threat level and the length of the aircraft path. The proposed method to construct optimal low-risk aircraft paths involves a simple geometric procedure and is very computationally efficient. The effectiveness of the developed algorithm is illustrated by a number of examples and comparisons with a fuzzy logic based algorithm.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Asynchronous Multirate Multisensor Data Fusion Over Unreliable
           Measurements With Correlated Noise
    • Authors: Lu Jiang;Liping Yan;Yuanqing Xia;Qiao Guo;Mengyin Fu;Kunfeng Lu;
      Pages: 2427 - 2437
      Abstract: In this paper, the problem of optimal state estimation is studied for fusion of asynchronous multirate multiscale sensors with unreliable measurements and correlated noise. The noise of different sensors is cross-correlated and coupled with the system noise of the previous step and the same time step. The system is described at the highest sampling rate with different sensors observing a single target independently with multiple sampling rates. An optimal state estimation algorithm based on iterative estimation of the white noise estimator is presented, which makes full use of the observation information effectively, overcomes the packet loss, data fault, unreliable factors, and improves the precision and the robustness of the system state estimation. A numerical example is used to illustrate the effectiveness of the presented algorithm.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • A Stand-Alone Approach for High-Sensitivity GNSS Receivers in
           Signal-Challenged Environment
    • Authors: Tiantong Ren;Mark G. Petovello;
      Pages: 2438 - 2448
      Abstract: To navigate in global navigation satellite systems (GNSS) signal-challenged environment, for example, foliage canopy, urban canyon, indoor, etc., high-sensitivity GNSS receivers are usually preferred for the improved acquisition and tracking capabilities. The core of high-sensitivity GNSS receiver design is to extend integration time coherently, which is optimal for improving post-signal-to-noise ratio, mitigating multipath and cross-correlation false locks, and avoiding squaring loss. In GNSS data channels, extending integration time coherently requires the navigation message data bit wipe-off. For stand-alone high-sensitivity GNSS receivers, bit wipe-off is usually achieved by using estimation algorithms (i.e., bit decoding) rather than accessing external networks (i.e., bit aiding). In this paper, the maximum-likelihood (ML) bit decoding is used to estimate the data bit values for bit wipe-off. Furthermore, the benefits of using advanced tracking algorithms-vector tracking and inertial navigation system (INS)-assisted tracking (i.e., ultratight coupling of GNSS/INS)-to improve ML bit decoding and navigation performance are analyzed. Two vehicular navigation tests are performed in dense foliage and an urban canyon environment. In the context of global positioning system L1 C/A signals, the field test results show that vector tracking and ultratight coupling can improve the successful decoding rate by up to 40% depending on signal strength. This paper also demonstrates how the signal power-based correlator selection method can address high bit error-rate problems when ML bit decoding is used for bit wipe-off in the signal-challenged environment. After implementing this algorithm, the position and velocity accuracy of the stand-alone high-sensitivity GNSS receiver has been improved about 50% after extending coherent integration time from 20 to 100 ms in the vehicular navigation tests.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Fast Detection of Compressively Sensed IR Targets Using Stochastically
           Trained Least Squares and Compressed Quadratic Correlation Filters
    • Authors: Brian Millikan;Aritra Dutta;Qiyu Sun;Hassan Foroosh;
      Pages: 2449 - 2461
      Abstract: Target detection of potential threats at night can be deployed on a costly infrared focal plane array with high resolution. Due to the compressibility of infrared image patches, the high resolution requirement could be reduced with target detection capability preserved. For this reason, a compressive midwave infrared imager (MWIR) with a low-resolution focal plane array has been developed. As the most probable coefficient indices of the support set of the infrared image patches could be learned from the training data, we develop stochastically trained least squares (STLS) for MWIR image reconstruction. Quadratic correlation filters (QCF) have been shown to be effective for target detection and there are several methods for designing a filter. Using the same measurement matrix as in STLS, we construct a compressed quadratic correlation filter (CQCF) employing filter designs for compressed infrared target detection. We apply CQCF to the U.S. Army Night Vision and Electronic Sensors Directorate dataset. Numerical simulations show that the recognition performance of our algorithm matches that of the standard full reconstruction methods, but at a fraction of the execution time.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Binary Frequency Shift Keying for Continuous Waveform Radar
    • Authors: Nadav Levanon;Itzik Izchak Cohen;
      Pages: 2462 - 2468
      Abstract: A new binary frequency-shift keying (BFSK) waveform is suggested for continuous wave radar. It provides ideal periodic autocorrelation (PAC) when processed by a matched filter, and perfect periodic cross-correlation (PCC) when processed by a mismatched filter. Ideal PAC implies a uniform sidelobe level, whose ratio to the PAC peak is equal to the inverse of the code length. Perfect PCC implies zero sidelobes. BFSK is relatively spectrum efficient. Design details and processing issues are discussed.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Solar Flare TDOA Navigation Method Using Direct and Reflected Light for
           Mars Exploration
    • Authors: Jin Liu;Jian-Cheng Fang;Gang Liu;Jin Wu;
      Pages: 2469 - 2484
      Abstract: In the capture period of deep space exploration, three traditional celestial navigation methods including the direction, velocity, and distance measurements cannot completely meet the requirement of navigation accuracy due to ephemeris errors. To solve this problem, considering the fact that some impulses exist in solar light irradiance profile due to solar flares, we propose the solar flare time difference of arrival (TDOA) measurement method, which exploits these impulses to measure the position of the spacecraft. As the time of arrival (TOA) of solar flare cannot be predicted, we cannot use the solar flare TOA directly. The Mars light irradiance variation is related to the solar one, as the Mars light is the solar light filtered by the Martian atmosphere absorption filter. Based on this theory, the solar flare TDOA measurement method using direct and reflected light is developed. In this method, two solar flare TOAs are obtained by the spacecraft. One is from the sun directly. The other is the corresponding TOA reflected by Mars. Their difference is the TDOA measurement. In addition, we also propose two alternative schemes. One uses the solar light instead of flare if solar flares do not occur in the capture period, and the other adopts Phobos as the reflected point instead of Mars to solve the Martian atmospheric absorption. The traditional direction measurement-based navigation method can provide highly accurate navigation information at the tangential direction in the capture period. However, its accuracy at the radial direction is very low. Fortunately, the solar flare TDOA measurement method offsets this problem. To get highly accurate navigation information, the solar flare TDOA measurement and the Mars direction measurement are coupled into the solar flare TDOA/Mars direction integrated navigation system. We present simulation results that demonstrate the feasibility and effectiveness of the solar flare TDOA measurement method. Compared to the traditional-direction measurement-based navigation method, the solar flare TDOA/Mars direction integrated navigation can provide higher positioning accuracy, especially the radial component.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • A Sparse Bayesian Learning Approach for Through-Wall Radar Imaging of
           Stationary Targets
    • Authors: Van Ha Tang;Son Lam Phung;Fok Hing Chi Tivive;Abdesselam Bouzerdoum;
      Pages: 2485 - 2501
      Abstract: Through-the-wall radar (TWR) imaging is an emerging technology that enables detection and localization of targets behind walls. In practical operations, TWR sensing faces several technical difficulties including strong wall clutter and missing data measurements. This paper proposes a sparse Bayesian learning (SBL) approach for wall-clutter mitigation and scene reconstruction from compressed data measurements. In the proposed approach, SBL is used to model both the intraantenna signal sparsity and interantenna signal correlation for estimating the antenna signals jointly. Here, the Bayesian framework provides a learning paradigm for sharing measurements among spatial positions, leading to accurate and stable antenna signal estimation. Furthermore, the task of wall-clutter mitigation is formulated as a probabilistic inference problem, where the wall-clutter subspace and its dimension are learned automatically using the mechanism of automatic relevant determination. Automatic discrimination between targets and clutter allows an effective target image formation, which is performed using Bayesian approximation. Experimental results with both real and simulated TWR data demonstrate the effectiveness of the SBL approach in indoor target detection and localization.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Optimal Datalink Selection for Future Aeronautical Telecommunication
           Networks
    • Authors: Atm S. Alam;Yim-Fun Hu;Prashant Pillai;Kai Xu;Jim Baddoo;
      Pages: 2502 - 2515
      Abstract: Modern aeronautical telecommunication networks (ATN) make use of different simultaneous datalinks to deliver robust, secure, and efficient ATN services. This paper proposes a multiple attribute decision making based optimal datalink selection algorithm, which considers different attributes including safety, QoS, costs, and user/operator preferences. An intelligent TRigger-based aUtomatic Subjective weighTing (i-TRUST) method is also proposed for computing subjective weights necessary to provide user flexibility. Simulation results demonstrate that the proposed algorithm significantly improves the performance of the ATN system.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Track-Before-Detect Strategies for Radar Detection in G0-Distributed
           Clutter
    • Authors: Wei Yi;Haichao Jiang;Thia Kirubarajan;Lingjiang Kong;Xiaobo Yang;
      Pages: 2516 - 2533
      Abstract: This paper considers target detection via dynamic-programming based track-before-detect (DP-TBD) for radar systems. The clutter is modeled usingenlr G0 distribution, which is usually used to model clutter received from high-resolution radars and radars working at small grazing angles. Two target models, namely, Swerling 0 and 1 models, are considered to capture the radar cross section changes over time. DP-TBD techniques that integrate amplitude suffer from significant performance loss in this case due to the high likelihood of target-like outliers. In this paper, the log-likelihood ratio (LLR) is used in the integration process of DP-TBD, taking the place of amplitude, to enhance radar detection performance. The expressions for the LLR for the above target models are derived first. However, neither of them has a closed-form solution. In order to reduce the complexity of evaluating the LLR, efficient but accurate approximation methods are proposed. Then the approximated LLR is used in the integration process of DP-TBD. Simulations are used to examine the efficiency of the approximation methods as well as the performances of different DP-TBD strategies.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Robust Constrained Attitude Control of Spacecraft Formation Flying in the
           Presence of Disturbances
    • Authors: Bahare Shahbazi;Maryam Malekzadeh;Hamid Reza Koofigar;
      Pages: 2534 - 2543
      Abstract: In this paper, the robust control problem for spacecraft formation flying in virtual structure algorithm is addressed. The effects of external disturbances, model uncertainties, sensor noises, and actuator saturation are taken into account. A robust controller based on μ-synthesis is first designed to overcome the environmental disturbances. To obtain a control law with lower order, an H∞-based linear matrix inequality controller is designed, using the linearized model with uncertainties. Then, a robust adaptive controller, based on the Lyapunov stability theorem, is presented to overcome a broader range of model uncertainties, which also guarantees the stability. From a comparison viewpoint, the numerical results are also demonstrated to show the performance of the robust controllers in tracking the desired attitude and position.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Multiple Sensor Measurement Updates for the Extended Target Tracking
           Random Matrix Model
    • Authors: Gemine Vivone;Karl Granström;Paolo Braca;Peter Willett;
      Pages: 2544 - 2558
      Abstract: In this paper, multiple sensor measurement update is studied for a random matrix model. Four different updates are presented and evaluated: three updates based on parametric approximations of the extended target state probability density function and one update based on a Rao-Blackwellized (RB) particle approximation of the state density. An extensive simulation study shows that the RB particle approach shows best performance, at the price of higher computational cost, compared to parametric approximations.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • A Bootstrapped PMHT with Feature Measurements
    • Authors: Qin Lu;Katherine Domrese;Peter Willett;Yaakov Bar-Shalom;Krishna Pattipati;
      Pages: 2559 - 2571
      Abstract: The probabilistic multi-hypothesis tracker (PMHT), a tracking algorithm of considerable theoretical elegance based on the expectation-maximization algorithm, will be considered for the problem of multiple target tracking with multiple sensors in clutter. In addition to position observations, continuous measurements associated with the unique, constant-and statistically unknown-feature of each target are incorporated to jointly estimate the states and features of the targets for the sake of tracking and classification, leading to a bootstrapped implementation of the PMHT. In addition, the information matrix for the stacked vector of states for all the targets at all the time steps during the observation time is derived.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Observer-Based Fault-Tolerant Attitude Control for Rigid Spacecraft
    • Authors: Bo Li;Qinglei Hu;Yanbo Yu;Guangfu Ma;
      Pages: 2572 - 2582
      Abstract: This paper addresses the problem of robust fault-tolerant control of spacecraft attitude stabilization in the presence of model uncertainties, actuator failures, and external disturbances simultaneously. Utilizing the fast nonsingular terminal sliding mode control technique, a novel finite-time extended state observer is first proposed to estimate and compensate for the specified synthetic uncertainties derived from actuator failures and/or model deviations. And also the detailed derivations of the observer are provided, along with a thorough analysis for the associated ultimately bounded stability and estimation error convergence property in the sense of finite-time control. Then, with the reconstructed information achieving from the finite-time observer, an adaptive robust sliding mode based fault-tolerant control approach is developed to ensure that the closed-loop attitude control system reach the real sliding mode surface in finite time. Meanwhile, the chattering problem has been restrained via the modified gain adjusting law. The key feature of the proposed strategies is that the whole closed-loop fault-tolerant control system can be guaranteed theoretically to be finite-time stable by the development of Lyapunov methodology. Finally, numerical simulation results are presented to illustrate and highlight the fine performance benefits obtained using the proposed schemes.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • GNSS Multireceiver Vector Tracking
    • Authors: Yuting Ng;Grace Xingxin Gao;
      Pages: 2583 - 2593
      Abstract: Accurate, reliable, and robust global positioning system (GPS) localization is desirable for many navigation applications. Unfortunately, it is challenging for a single GPS receiver to always provide accurate positioning solutions. In urban environments, intermittent signal availability leads to degraded GPS signal tracking and position estimation of the single GPS receiver. In addition, equipment malfunction of the single GPS receiver results in inaccurate navigation solutions. This paper presents a deeply coupled multireceiver vector tracking (MRVT) architecture that improves the reliability and robustness of GPS signal tracking and position estimation. MRVT jointly tracks GPS signals received by multiple GPS receivers, mitigating GPS signal tracking disruptions, improving the reliability of GPS localization in periods of intermittent signal availability. In addition, the MRVT receiver is more robust to equipment malfunctions than the single GPS receiver. We implemented an MRVT receiver using commercial radio frequency front ends and our PyGNSS software. We experimentally validated the reliability of our MRVT receiver in periods of intermittent GPS availability experienced in downtown San Francisco. Our MRVT receiver exhibited consistent GPS signal tracking and position estimation as compared to vector tracking. In addition, we experimentally validated the robustness of our MRVT receiver to the failure of a single GPS receiver.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Constrained Dynamic Systems: Generalized Modeling and State Estimation
    • Authors: Linfeng Xu;X. Rong Li;Yan Liang;Zhansheng Duan;
      Pages: 2594 - 2609
      Abstract: Due to physical laws or mathematical properties the states of some dynamic systems satisfy certain constraints, and taking advantage of such constraints generally will produce more accurate system models. This paper is concerned with dynamic modeling and state estimation of equality constrained systems. First, an effective framework for constrained dynamic modeling is proposed by which equality constraints and an original dynamics are optimally fused. In particular, modeling of linear and quadratic equality constrained dynamic systems is systematically investigated. Meanwhile, the effects of the original dynamics on the constructed dynamic model are analyzed. Next, properties of the constrained state estimation are presented, and in particular, the constrained minimum mean square error (CMMSE) estimator is proposed and its differences from the conventional constrained estimators are illustrated. Finally, the proposed modeling is assessed on benchmark scenarios of road-confined vehicle tracking. Simulation results demonstrate that the proposed CMMSE estimator outperforms the conventional constrained ones.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Phase Retrieval Approach for DOA Estimation With Array Errors
    • Authors: Wenyi Wang;Renbiao Wu;Junli Liang;Hing Cheung So;
      Pages: 2610 - 2620
      Abstract: Direction-of-arrival estimation in the presence of gain and phase errors is investigated from the phase retrieval (PR) perspective. In order to remove the influence of phase errors, they are isolated by taking the absolute values of the elements in the compensated covariance matrix. Finally, the formulated nonconvex PR optimization problem is solved by utilizing the feasible point pursuit algorithm. Simulation results demonstrate the effectiveness of the proposed algorithm.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Impact-Time-Control Guidance Law With Constraints on Seeker Look Angle
    • Authors: In-Soo Jeon;Jin-Ik Lee;
      Pages: 2621 - 2627
      Abstract: An impact-time-control guidance (ITCG) law is required for simultaneous attack of multiple missiles. In application of ITCG, the limit of seeker look angle should be regarded as an important factor in homing engagement scenarios. To avoid the loss of target tracking during engagement, the seeker's look angle should be confined to the seeker's field-of-view limit. This paper suggests a new ITCG law for a realistic situation with constraints on seeker look angle driven by the exact nonlinear equations of motion in plane. The proposed guidance law ensures the seeker's look angle to reduce monotonically from the initial value to zero at the intercept point. The resulting solution is presented in the form of proportional navigation guidance law with a time-varying navigation gain. The closed-form navigation gain can be obtained from information on the current missile-to-target range and heading angle.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Noncoherent Radar Detection in Correlated Pareto Distributed Clutter
    • Authors: Graham Victor Weinberg;
      Pages: 2628 - 2636
      Abstract: Radar detection in the presence of spatially correlated Pareto distributed clutter is examined. It is shown how an order-statistic-based sliding window detection process must have its threshold set in order to achieve a constant false alarm rate. A particular multivariate Pareto distribution is constructed, based upon a compound Gaussian model with inverse gamma texture, whose pairwise marginal distributions have a general correlation. A specific example is then used for performance analysis.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • New Phase Error Corrections for PFA with Squinted SAR
    • Authors: Matthew D. Scherreik;LeRoy A. Gorham;Brian D. Rigling;
      Pages: 2637 - 2641
      Abstract: The polar format algorithm, while being more efficient than backprojection for synthetic aperture radar image formation, produces images with distortion and defocus. Since these errors are caused by uncompensated phase, a correction may be applied in postprocessing. Recent work utilizes a slow-time Taylor expansion of the differential range to derive the residual quadratic phase error for broadside linear flight paths. In this letter, we extend this approach to squinted linear flight paths and present new distortion and defocus corrections.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Technical Areas and Editors: AESS IEEE Aerospace & Electronic Systems
           Society
    • Pages: 2642 - 2647
      Abstract: Presents a listing of the AESS technical editors and their areas of specialty.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
  • Information for Authors
    • Pages: 2648 - 2649
      Abstract: These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal.
      PubDate: Oct. 2017
      Issue No: Vol. 53, No. 5 (2017)
       
 
 
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