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IEEE Antennas and Wireless Propagation Letters
Journal Prestige (SJR): 1.047
Citation Impact (citeScore): 4
Number of Followers: 87  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1536-1225
Published by IEEE Homepage  [228 journals]
  • IEEE Antennas and Wireless Propagation Letters

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      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: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Pattern Synthesis With Closed-Form Array Response Control Algorithms

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      Authors: Xue Shi;
      Pages: 1507 - 1511
      Abstract: In this letter, the problem of array pattern synthesis is considered by developing two array response control algorithms. The devised two algorithms build on the basis of the accurate array response control approach, and both of them have closed-form solutions and low computational complexities. More specifically, the first proposed algorithm realizes multipoint array response control from an any given weight vector, and the second algorithm modifies the first one by avoiding the possible beam axis shift. The proposed two algorithms are able to control array responses accurately under the conditions of independence on steering vectors. By applying the first and the second array response control algorithm, two effective pattern synthesis methods for focused patterns and shaped patterns are devised, respectively. Representative examples are presented to demonstrate the performance of the proposed algorithms in array response control and pattern synthesis.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Dual-Mode Patch Antenna With Capacitive Coupling Structure for
           On-/Off-Body Applications

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      Authors: Guo-Ping Gao;Zhi-Heng Dou;Zhuo-Qi Yu;Ben-Kai Zhang;Jing-Hang Dong;Bin Hu;
      Pages: 1512 - 1516
      Abstract: A dual-band dual-mode antenna for on-/off-body centric communications is proposed for 2.4 and 5.8 GHz industrial scientific medical bands. Using polydimethylsiloxane as substrate, the proposed antenna has a compact structure and is easy to wear. The on-body mode is realized by a circular patch loaded with four symmetrically distributed metallic vias to generate TM$_{mathbf{01}}$ mode located on the lower substrate. The off-body mode is achieved by a smaller circular patch on the top of the upper substrate, which generates a directional radiation pattern by exciting its TM$_{mathbf{11}}$ mode. The measured operating bandwidths of the proposed antenna in two bands are 90 MHz (2.40–2.49 GHz) and 330 MHz (5.63–5.96 GHz), respectively. Average gain for the on-body mode is $-$2.38 dBi and for the off-body mode is 6.67 dBi. In addition, the antenna exhibits a robust performance near human tissue and low specific absorption rate values.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Quasi-Deterministic Channel Propagation Model for 60 GHz Urban Wi-Fi
           Access From Light Poles

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      Authors: Sung Yun Jun;Chiehping Lai;Derek Caudill;Jian Wang;Jelena Senic;Neeraj Varshney;Camillo Gentile;
      Pages: 1517 - 1521
      Abstract: There is strong impetus by the Telecom Infra Project to exploit the 60 GHz unlicensed band for public Wi-Fi in urban environments, by installing access points on light poles. Although many 60 GHz urban channel measurements have been recorded to date, they have resulted only in path loss models or root-mean-square (RMS) delay spreads. What is needed at millimeter-wave is a spatially consistent channel model for beamtracking that embodies the characteristics of these short wavelengths—sparsity and rough surface scattering—such as the Quasi-Deterministic model. In this letter, we fit the model to channel measurements we recorded in an urban environment. The measurements were recorded at 4, 6, and 9 m antenna heights to investigate the tradeoffs between light pole heights. The large-scale channel metrics between the model and the measurements were shown to match very well.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Backward-to-Forward Scanning Periodic Nonuniform Leaky-Wave Antenna for
           Reflected Sidelobe Suppression

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      Authors: Kexin Mao;Yuanxin Li;Zhixi Liang;Shao Yong Zheng;Yunliang Long;
      Pages: 1522 - 1526
      Abstract: A backward-to-forward continuous beam scanning periodic leaky-wave antenna (PLWA) with eliminated reflected sidelobe in both forward and backward quadrant is presented in this letter. The proposed antenna consists of ten nonuniform unit cells (UCs) composed of orthogonally bending transmission lines. The open stopband is suppressed by optimizing the impedance matching through adjusting the widths of two transversal lines in UC. Gradient change in the geometries of the UCs along the direction of propagation is applied to achieve reflected sidelobe suppression. A prototype of the antenna is simulated, fabricated, and measured. The measured results show that the main beam scans continuously from −51° to +60° in the frequency band of 3.7–6.5 GHz. The proposed antenna features a low reflected sidelobe level in both forward quadrant and backward quadrant, and achieves a maximum reduction of 7.9 dB at 6.5 GHz compared to the conventional uniform PLWA.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Enabling mmWave Wireless Rack Area Networks: Channel Characterization
           Within a Server Rack

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      Authors: Mohammed Zakarya Zaaimia;Larbi Talbi;Mourad Nedil;
      Pages: 1527 - 1531
      Abstract: This letter presents 60 GHz radio measurements and channel characterization for wireless rack area network (WRAN) application within a networking enclosure, commonly known as a server rack. The propagation characterization is conducted with wideband and narrowband measurements to characterize the propagation phenomena and investigate the feasibility of a reflected non-line-of-sight (RNLoS) link. The impact of obstruction by networking cables and a human hand is also investigated to extract the fading depth, fading rate, and the time varying shadowing. The implications on WRAN system design are accordingly deduced. It is found that optimal RNLoS channel response is characterized by a clustering effect with a 7.82 dB reflection loss. The obstruction by networking cables introduces significant channel dispersion and contributes to significant fading depth and fading rate values.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A High-Efficiency Dual-Band Self-Filtering Antenna Based on Three Dense
           Dielectric Strip Resonators

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      Authors: Kai Xu;Lixin Jin;Hui Tang;Wen-Wen Yang;Jin Shi;
      Pages: 1532 - 1536
      Abstract: A high-efficiency dual-band dielectric filtering antenna based on three parallel placed dense dielectric strip resonators (DDSRs) is proposed for the self-filtering property. That means both the filtering responses of the two bands are only determined by the three DDSRs themselves without extra filtering circuits. The even-mode coupling of the TM1δ mode (TM3δ mode) between the middle and two-sided DDSRs is used to form the first (second) radiation band, while the odd-mode coupling contributes one radiation null at the upper edge of each radiation band. Therefore, the proposed dual-band dielectric antenna exhibits relatively high total efficiency benefited from the self-filtering characteristic. Additionally, the presented one without extra filtering circuits obtains the features of low profile, enhanced bandwidth, and gain. For test and verify, a prototype was measured at 7.7 and 13.35 GHz with the fractional bandwidths of 11.4% and 4.8%, the peak gains of 7.65 and 10.5 dBi, and the total efficiencies of 89% and 87%, respectively. Radiation nulls are generated at 8.5 and 13.8 GHz, respectively.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Millimeter-Wave Frequency-Reconfigurable Fabry–Pérot
           Cavity Antenna

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      Authors: Min Li;Muhammad Yasir Jamal;Xiaoqiang Li;Kwan Lawrence Yeung;Lijun Jiang;Tatsuo Itoh;Ross Murch;
      Pages: 1537 - 1541
      Abstract: This letter introduces a method for implementing a frequency-reconfigurable Fabry–Pérot cavity (FPC) antenna utilizing polarization standing waves (PSWs). The PSW is supported by two metasurfaces (MSs) at cavity ends. The resonant condition allows the antenna to have frequency-reconfigurable characteristic by mechanically rotating the top MS around the center and relative to the bottom MS, without adjusting the physical dimension. The antenna is prototyped at 60 GHz for millimeter-wave applications. Simulated and measured results demonstrate that a tunable frequency range of 60.8–66.2 GHz with a maximum boresight gain of around 22.2 dBi can be attained, verifying the antenna concept.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Synthesis of Simultaneous Sum and Difference Patterns in Single-Channel
           1-Bit Time-Modulated Array

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      Authors: Qianwei Zeng;Peng Yang;Xuanyu Lu;Mingwei Luo;Yunying Man;Feng Yang;Shiwen Yang;
      Pages: 1542 - 1546
      Abstract: In this letter, a novel synthetic approach for simultaneous sum and difference patterns based on a single-channel 1-bit time-modulated array (TMA) is proposed. A series of asymmetric 1-bit modulating waveforms suited for monopulse systems is generated by theoretically analyzing the formation circumstances of simultaneous sum and difference patterns. The designed sum and difference patterns have equivalent radiated power as compared to the state-of-the-art approaches, and the TMA has a good power conversion efficiency. Furthermore, because the sum and difference patterns are synthesized at the first positive and negative sidebands, respectively, the signal allowed transmission bandwidth is enhanced when the switching speed is taking into account. Modulation schemes for different scenarios are provided to show the feasibility and effectiveness.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Efficient Characteristic Mode Analysis for PEC Objects Using
           Sherman–Morrison–Woodbury Formula-Based Algorithm

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      Authors: Liyang Zhang;Xinlei Chen;Ziwei Li;Wenchao Fu;Changqing Gu;
      Pages: 1547 - 1551
      Abstract: In characteristic mode analysis (CMA), solving the characteristic modes (CMs) from the generalized eigenvalue problem takes the main part of the workload. In this letter, the algorithm based on the Sherman–Morrison–Woodbury (SMW) formula is embedded into the implicitly restarted Arnoldi method to improve the efficiency of solving the CMs. In this method, the impedance matrix is compressed into a product of block-diagonal matrices by using the SMW formula with adaptive cross approximation algorithm. Benefiting from the efficient compression, calculating the inverse matrix of the impedance matrix and the matrix vector products related to the solution of the generalized eigenvalue problem is accelerated. Consequently, the computational time and memory requirement in CMA are both reduced. Some numerical examples are demonstrated to show the accuracy and efficiency of the proposed method.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Wideband Filtering Dielectric Resonator Antenna Based on the HEM 11δ
           Mode

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      Authors: Dong-Sheng La;Chao Zhang;Yu-Jiao Zhang;Ting-Xue Jiang;Mei-Jun Qu;Jing-Wei Guo;
      Pages: 1552 - 1556
      Abstract: In this letter, a wideband filtering dielectric resonator antenna (DRA) based on the HEM11δ mode is proposed with high roll-off rate and flat gain response in the whole passband. The proposed filtering DRA is excited by a simple feed structure composed of a driven ring, a parasitic ring and a driven arc. Each of them can excite the HEM11δ mode at different resonant frequencies, thus enlarging the impedance bandwidth of the proposed filtering DRA. Since the three resonant frequencies belong to the same mode, stable radiation pattern can be achieved simultaneously. In addition, two radiation nulls are generated near the lower and upper edges of the passband by the feed structure, making the proposed DRA obtain high frequency selectivity. All the three resonant frequencies and two radiation nulls are independently adjustable. A prototype has been fabricated and measured for demonstration, and the measured results are coincided with the simulated ones.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Characteristic Mode Formulations of Composite PEC and Lossy Dielectric
           Objects

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      Authors: Qi Wu;
      Pages: 1557 - 1561
      Abstract: Lossy dielectric substrate affects the performance of a nearby perfect electric conductor (PEC) antenna. This letter presents a set of formulae for characteristic mode analysis (CMA) of composite PEC and lossy dielectric objects. It is based on the volume-surface integral equation and substructure treatment that separates the radiation and dissipation powers of the composite structure. A narrow PEC plate (that represents a dipole antenna) is placed in proximity of a thick, lossy dielectric material, and CMA of this structure is presented as an example. The separation gap between the PEC and dielectric objects affects the resonance and radiation efficiency of the antenna, and it is shown that CMA accurately captures those effects. The influence of dielectric loss on the modal orthogonality is discussed. Since the PEC item dominates over the coupling one in the substructure operator, the computed modes maintain good orthogonality with low-loss dielectrics. Owing to the physical insights of CMA, it has many potential applications associated with lossy materials.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Regression of Large-Scale Path Loss Parameters Using Deep Neural Networks

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      Authors: Mustafa Bal;Ahmed Marey;Hasan F. Ates;Tuncer Baykas;Bahadir K. Gunturk;
      Pages: 1562 - 1566
      Abstract: Path loss exponent and shadowing factor are among important wireless channel parameters. These parameters can be estimated using field measurements or ray-tracing simulations, which are costly and time-consuming. In this letter, we take a deep neural network-based approach, which takes either satellite image or height map of a target region as input, and estimates the desired channel parameters. We use the well-known VGG-16 architecture, pretrained on the ImageNet dataset, as the backbone to extract image features, modify it as a regression network to produce channel parameters, and retrain it on our dataset, which consists of satellite image or height map as input and channel parameters as target values. We demonstrate that deep networks can be successfully utilized in estimating path loss exponent and shadowing factor of a region, simply from the region’s satellite image or height map. The trained models and test codes are publicly available on a Github page.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Compact Wideband Circularly Polarized Loop Antenna Based on Dual Common
           and Differential Modes

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      Authors: Zhan Chen;Wei Hu;Yuchen Gao;Lehu Wen;Changjiang Li;Zhipeng Hu;Wen Jiang;Steven Gao;
      Pages: 1567 - 1571
      Abstract: This letter presents a novel design method of a compact wideband loop antenna for circularly polarized (CP) radiation based on two sets of common modes (CMs) and differential modes (DMs). Different CMs and DMs are excited in the loop antenna with the same amplitude of radiated electric fields by using equal-amplitude and in-phase excitation. A wideband CP radiation performance is achieved through the combination of two sets of CMs and DMs with an innate 90° phase delay. Moreover, the shared-aperture configuration of CMs and DMs achieves a size reduction. An experimental prototype was fabricated and measured to verify the design concept for CP operation. The experimental results indicate that an overlapped bandwidth of 2.30–3.40 GHz (38.6%) with |S11|
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Compact Dual-Band Dual-Circularly Polarized SIW Cavity-Backed Antenna
           Array for Millimeter-Wave Applications

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      Authors: Chuanming Zhu;Guanghui Xu;Aidi Ren;Wei Wang;Zhixiang Huang;Xianliang Wu;
      Pages: 1572 - 1576
      Abstract: A compact millimeter-wave (mm-Wave) dual-band dual-circularly polarized (CP) antenna based on substrate integrated waveguide (SIW) cavity-backed structure is proposed in this letter. By introducing the square aperture with two symmetric perturbation notches on the SIW cavity, right-hand CP (RHCP) can be generated at the low frequency band. On this basis, the dumbbell-shaped patch is placed inside the square aperture to generate left-hand CP (LHCP) at the high frequency band. To optimize the impedance matching and adjust resonant frequency, stacked parasitic patches are adopted. In addition, the two shorted vias are introduced to realize the independent tuning of high frequency band. The measured results show that the array achieves the impedance bandwidths of 7.3% and 7.5%, AR bandwidths of 2.8% and 2.6%, with gains of 18.2 and 18.5 dBic at 28 and 38 GHz, respectively. The proposed array will be a potential candidate component for 5G mm-Wave full-duplex wireless communication systems.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Compensation Method of Nonideal Modulation Pulse for Direction Finding
           With Time-Modulated Array

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      Authors: Han Liu;Jingfeng Chen;Xianling Liang;Ronghong Jin;
      Pages: 1577 - 1581
      Abstract: In this letter, a direction-finding compensation method of nonideal modulation pulse for direction finding with the time-modulated array is investigated. With the transmission signal's increasing bandwidth, the conventional rectangular pulse cannot effectively describe the practical modulation pulse envelope shape, which will introduce the direction-finding error caused by the different harmonic characteristics. For compensating the error, a modeling method for the practical modulation pulse envelope shape is investigated and its harmonic expression is also deduced. Compared with the direction-finding method considering the rectangular pulse, numerical simulation, and experiment results are provided to verify the effectiveness of the proposed compensation method.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Wideband 3-D-Printed Multibeam Circularly Polarized Ultrathin Dielectric
           Slab Waveguide Luneburg Lens Antenna

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      Authors: Siyuan Lei;Gao Wei;Kangkang Han;Xianlei Li;Tiancheng Qiu;
      Pages: 1582 - 1586
      Abstract: This letter presents a wideband three-dimensional (3-D)-printed circularly polarized (CP) ultrathin dielectric slab waveguide (DSW) Luneburg lens (LL) with multibeam application in X-band. The characteristic that DSW supports TE0 and TM0 waves to pass through with different phase constants is used to generate 90° phase difference to compose CP wave for the proposed structure. To prove the point, the prototype antenna is fabricated by 3-D printing and measured. The results show that the proposed LL supports multibeam application with 11 beams covering ±60° range in azimuth plane, and the 3 dB axial ratio bandwidth for multibeam antenna is 23.5% with reflection coefficient lower than −10 dB and gain higher than 13.7 dBi. The measured results show good coincidence with simulated ones.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Minimally Invasive Microwave Ablation Antenna With Highly Localized
           Ablation Zone

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      Authors: Li Wang;Xiue Bao;Yafei Wang;Sen Yan;Anxue Zhang;
      Pages: 1587 - 1591
      Abstract: This letter proposes a novel inexpensive microwave ablation (MWA) antenna with a highly localized ablation zone. The antenna is designed based on a substrate integrated coaxial line, at the end of which a serpentine structure is used to radiate microwave power. The serpentine structure can effectively shorten the length of the radiation structure, making the ablation zone more localized. Due to its simple structure, a convenient and inexpensive printed circuit board technology can be used to fabricate the disposable ablation probe. In addition, the proposed topology has a small cross section and, thus, is very suitable for minimally invasive surgery. Simulation analysis and validation experiments have shown that the proposed MWA antenna can provide reliable performance, which means that it can serve as a promising candidate for minimally invasive ablation therapy.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Bidirectional Scanning Antenna Based on Surface Wave Mode

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      Authors: Feiyu Ge;Hongxin Zhao;Shunli Li;Xiaoxing Yin;
      Pages: 1592 - 1596
      Abstract: A bidirectional scanning antenna (BSA) based on surface wave mode is proposed. The bidirectional scanning capacity is achieved by two back-to-back placed frequency scanning tapered slot antenna (FSTSA) elements. The corrugated slot array in inner edges enables the BSA to support two surface wave modes to propagate along the inner edges with different phase constants. Due to the dispersion characteristic of surface wave mode, the phase difference between two modes varies with frequencies, then frequency scanning is achieved at the endfire. Slot arrays are also etched on the outer edges to reduce current flowing. By separately configuring two back-to-back FSTSA elements, the BSA could form a rotationally symmetrical, mirror symmetrical, or asymmetrical bidirectional scanning pattern. Three prototypes with rotationally symmetrical, mirror symmetrical, and asymmetrical pattern are designed and fabricated to verify the principles. Since the scanning plane is parallel to antenna surface, the proposed BSA has a low cross section, which makes it suitable for wireless communication in tunnels and coal mines where good air ventilation is required.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Ka-Band Leaky-Wave Antenna Array With Stable Gains Based on HMSIW
           Structure

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      Authors: Yunjie Geng;Junhong Wang;Yujian Li;Zheng Li;Meie Chen;Zhan Zhang;
      Pages: 1597 - 1601
      Abstract: In this letter, a Ka-band leaky-wave antenna array based on half-mode substrate integrated waveguide (HMSIW) structure is proposed, which is capable of scanning beam from backward to forward including broadside with stable gains. This array is fed by a SIW-to-HMSIW power-divider and consists of two back-to-back HMSIWs with one row of sinusoidally modulated vias, which can excite the first-space harmonic radiation. Periodic slots are designed at the edge of top-wall to suppress the open stopband and etched on the ground to enhance the scanning rate using the slow-wave effect. The measured results validate that when the operating frequency changes from 27 GHz to 40 GHz, the proposed array has the beam scanning from –40° to 30° with the peak gain varies from 13.4 to 15 dBi.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • TMA–FDA Range-Angle Beamforming With Periodic Linear-Phase
           Time-Modulating Waveforms

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      Authors: Roberto Maneiro-Catoira;Julio Brégains;José Antonio García-Naya;Luis Castedo;
      Pages: 1602 - 1606
      Abstract: Frequency diverse arrays (FDAs) provide range-angle time-invariant transmit–receive beamforming, although a fine focus of their radiation patterns is costly since high-resolution mixers and phase shifters are required. An innovative approach to FDAs is proposed in which mixers and phase shifters are replaced by the application of periodic linear-phase time-modulating waveforms to the antenna excitations implemented with 2-bit variable phase shifters controlled with periodic on–off instants of binary sequences, which leads to a simple and precise method for FDA beam focusing.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Noise Figure of an Active Antenna Array and Receiver System

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      Authors: Karl F. Warnick;
      Pages: 1607 - 1609
      Abstract: Progress has been made in extending traditional antenna terms to complex phased array receivers, but a satisfactory definition for the noise figure of an active antenna and receiver system has not yet been given. This is particularly so for the case of a complex phased array with electronic gains in each signal path and beams formed using digital signal processing. We provide a simple definition for the active antenna and receiver noise figure, which is consistent with existing active antenna terms. The active antenna noise figure can be measured using the antenna Y-factor technique.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Electronically Controlled Fixed-Frequency Beam-Scanning Periodic
           Leaky-Wave Antenna With Positive-Order-Harmonic Radiations

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      Authors: Shanzhe Wang;Zheng Li;Meie Chen;Junhong Wang;
      Pages: 1610 - 1614
      Abstract: An electronically controlled fixed-frequency beam-scanning periodic leaky-wave antenna operating in a millimeter-wave band is presented in this letter. An air-filled gap waveguide (GW) base is employed as a millimeter-wave excitation thanks to its low-loss property. Totally, 60 patches in a staggered two-row arrangement are introduced as the radiating elements, which get energies from the GW through longitudinal slots etched on the middle metal layer, and this produces reverse phases in the two rows under a TE10-mode excitation. Then, a method by constructing an equivalent phase constant is developed in this letter, and positive-order-harmonic radiation is used to analyze the radiation property. By introducing the period-reconfigurable method, a fixed-frequency beam-scanning performance is achieved. In addition, the developed antenna is fabricated and experiments have been implemented. A beam-scanning range of 70° from −35° to 35° is realized using the positive-order-harmonic radiations at 29 GHz, and the measured peak gain arrives at 16.5 dBi. The design shows possible applications in millimeter-wave communications.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Decomposition-Based Analysis of Wireless Multipath Channel With
           Full-Wave Simulation

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      Authors: Shuchen Wang;Suixiang Gao;Fei Qin;Wenguo Yang;
      Pages: 1615 - 1619
      Abstract: Along with the adaptation of the modern communication theory, the in-depth understanding of multipath fading channel is necessary to guarantee the efficient design of both algorithms and systems, especially the multiple-input--multiple-output (MIMO) system. This letter proposes a novel decomposition-based method aiming to achieve the accurate multipath channel analyses with full-wave simulation. Through the sequential deleting of scatters in the environments, the complex multipath channels can be decomposed, where the accurate delay and strength can be calculated from the recorded electronic fields along the sweeping of incident frequency. Then, the latent multipath components can be simply located along the decomposition. The proposed method can also provide the geographical distributions of channel responses, which are important to guild the MIMO system design.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Shared-Aperture Dual-Band High-Efficiency Antenna Based on Groove Gap
           Waveguide

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      Authors: Yang Cheng;Yuandan Dong;
      Pages: 1620 - 1624
      Abstract: A shared-aperture dual-band antenna at 2.4 GHz Wi-Fi and Ku-bands is proposed in this letter. The antenna in the high-frequency band is featured by a slotted cavity configuration based on the gap waveguide technology. The slotted antenna consists of 3 × 3 slots incorporated into the top metal of the cavity. The periodic structure is loaded into the proposed antenna, which reduces the resonant frequency of the cavity. The top metal of the cavity is enlarged and four shorted screws are loaded, which achieve four half-mode cavities operated in the Wi-Fi band. Two antennas (slotted cavity antenna and dual-band antenna) are designed, fabricated, and tested. Measured results show that a −10 dB impedance bandwidth of 18.3% (13.15–15.8 GHz), a 3 dB gain bandwidth of 17.7% (13.1–15.65 GHz), and a peak gain of 14.8 dBi are realized for the cavity antenna. The impedance bandwidth of the proposed dual-band antenna covers 2.4–2.5 and 13.4–16.2 GHz. A 2 dB gain bandwidth of 16.4% (13.4–15.8 GHz) is realized. Owing to an all-metal structure that exhibits no dielectric loss, the radiation efficiency of the antenna is better than −1 dB in the whole working band. The proposed antenna shows the characteristics of high gain, high efficiency, and low cost, which is suitable for simultaneous satellite communication and Internet of Things applications.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • RMOCG: A Riemannian Manifold Optimization-Based Conjugate Gradient Method
           for Phase-Only Beamforming Synthesis

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      Authors: Kai Zhong;Jinfeng Hu;Yang Cong;Guolong Cui;Haotian Hu;
      Pages: 1625 - 1629
      Abstract: The phase-only null beamforming synthesis is widely used in communication, radar, and sonar. Due to the phase-only constraint (constant modulus constraint), the problem is nonconvex and NP-hard. The existing methods mainly solve the problem in an indirect way, by relaxing the problem to a more tractable form. Nevertheless, these methods either need huge computational cost or degrade the performance. To break the tradeoffs between the performance and computational complexity, a direct method is proposed without relaxation. In the proposed method, the problem is first transformed into an unconstrained problem on a complex circle manifold. Then, by deriving the gradient descent direction and the step size, a Riemannian manifold optimization-based conjugate gradient algorithm is derived to obtain the direct solution for the transformed problem. Compared with the existing methods, the proposed method can achieve 4 dB null gain reduction and 1 magnitude complexity decreasing.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Surrogate Modeling Technique Based on Space Mapping for Radar Cross
           Section

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      Authors: Tianxu Yan;Dongying Li;Wenxian Yu;
      Pages: 1630 - 1633
      Abstract: A novel surrogate model is proposed based on space mapping to maintain accurate predictions of the radar cross section over a relative large range of frequencies. With a sparse-sample full-wave solver and a dense-sample ray-tracing solver, the surrogate model can be established with a small computational burden. A mapping function is introduced to represent the relationship between two such solvers to overcome the limitations of the conventional fixed linear mapping form. Two numerical examples are used to verify the effectiveness of the proposed method, which demonstrate its ability to achieve an ideal accuracy with limited computational resources.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Design of mmWave Foldable Vertically Stacked Yagi–Uda Antenna Inspired
           by Origami and Kirigami Theories

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      Authors: Nohgyeom Ha;Gyoungdeuk Kim;Nathan S. Jeong;Sangkil Kim;
      Pages: 1634 - 1638
      Abstract: This letter presents a foldable vertically stacked Yagi–Uda antenna at millimeter-wave (mmWave) frequency band. The proposed antenna is built on a FR4 substrate. The antenna consists of a balun, feed dipole element, stacked folded dipole, and inside lamina emergent torsional (LET) joint array. The LET joint array is introduced to reduce and distribute the mechanical stress generated in folding the rigid FR4 substrate. In the planar mode, the antenna results in a measured gain value of 4.9 dBi at the design frequency 24 GHz with a cross-polarization suppression level of less than 12 dB. In the folded mode, the antenna has a measured gain value of 3.9 dB at the target frequency 24 GHz with a cross-polarization suppression level of less than 10 dB. Both operation modes of the proposed antenna cover the broad bandwidth from 23 to 28 GHz (about 20$%$).
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Surface-Wave Minimization Using Spherical Wave Expansion

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      Authors: Albert Salmi;Anu Lehtovuori;Ville Viikari;
      Pages: 1639 - 1643
      Abstract: This letter presents a method for reducing antenna-excited surface waves in mobile devices. Surface waves are canceled either by actively injecting compensating surface waves in opposite phase, or passively creating reactive conditions from which scattered, secondary surface waves cancel the primary waves. We use spherical wave expansion to calculate the amplitudes and phases of the canceling surface waves and show also how reactive loading near the antenna can launch these canceling waves. We verify the proposed method with simulations. Reduced surface waves result in a smoother radiation pattern and significantly increased gain.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Circularly Polarized Waveguide Aperture Array Antenna With a Wide Axial
           Ratio Bandwidth

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      Authors: Hai Wang;Xue Lei;Tian-dong Duan;Tian-peng Li;Ming-yang Zhao;Jun Gao;Pan Lu;
      Pages: 1644 - 1648
      Abstract: In this letter, we design a circularly polarized (CP) waveguide aperture antenna with a wide axial ratio bandwidth. The unit is composed of three waveguides with different rotation angles and width. The reflected and transmitted orthogonal electric fields are superimposed on the asymmetric plane of the rotating structure in each layer, which not only reduces energy reflection but also promotes the decomposition of the electric field with the same amplitude and the phase difference 90$^circ$ in different rotating waveguides. Finally, a CP electric field is formed on the antenna’s surface. The phase difference and amplitude difference of orthogonal electric field are approximately 90$^circ$ and less than 1.2 dB, respectively. In addition, the different width of the waveguide plays a role in impedance matching. A 2 × 2 array is fabricated and measured to verify the validity of the design. The measured results show good agreement with the simulation. Measured impedance bandwidth of 37.9% (27.5–40.4 GHz), axial ratio bandwidth of 41.2% (27–41 GHz), and a gain of 15.7 dBi at center frequency have been obtained.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Wideband Leaky-Wave Lens Antenna With Annular Corrugations in the Ground
           Plane

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      Authors: Sjoerd Bosma;Nick van Rooijen;Maria Alonso-delPino;Nuria Llombart;
      Pages: 1649 - 1653
      Abstract: We present a resonant leaky-wave lens antenna, fed by a circular waveguide with annular corrugations in the ground plane. The proposed leaky-wave feed reduces the impact of the spurious TM0 leaky-wave mode in all planes over a wide bandwidth while reducing assembly complexity compared to previous methods. The proposed leaky-wave antenna has an aperture efficiency above 80%, a return loss below −15 dB, and a cross-polarization level below −20 dB over a bandwidth from 110–220 GHz (2:1). We have fabricated and measured a WR-5 band (140–220 GHz) antenna prototype with a lens diameter of 3 cm that achieves excellent agreement between measurement and simulation in terms of return loss, directivity, and gain.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Compact High-Selectivity Wideband Filtering Antenna With Multipath
           Coupling Structure

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      Authors: Bing-Jie Chen;Xue-Song Yang;Bing-Zhong Wang;
      Pages: 1654 - 1658
      Abstract: A compact wideband filtering patch antenna with high selectivity is presented. The proposed filtering antenna contains a rectangular patch rounded by a pair of U-shaped patches, and is fed through two coupling slots etched on the ground. By introducing these elements, four in-band resonances are generated and the impedance bandwidth are expanded. Besides, multiple coupling paths are constructed from the feeding port to the radiating patches to form three radiation nulls at the band edges. Moreover, a modified composite right/left-handed transmission line unit is used as the feedline to further suppress the out-of-band radiation level. The performance of the proposed filtering antenna is verified by both simulation and measurement. It exhibits a 21.5% (4.45–5.52 GHz) measured impedance bandwidth with a compact size of 0.4 λ0 × 0.4 λ0 (where λ0 is the free-space wavelength at 5 GHz). Besides, the measured average gain and out-of-band suppression level are 4.8 dBi and 15.9 dB, respectively. Obviously, this filtering antenna can be used to build a compact multiband antenna array to reduce the interference between different bands.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Low-RCS and Wideband Circularly Polarized Array Antenna Co-Designed With
           a High-Performance AMC-FSS Radome

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      Authors: Zhiyu Xing;Feng Yang;Peng Yang;Jianhua Yang;
      Pages: 1659 - 1663
      Abstract: In this letter, we investigate a low radar cross-section (RCS) wideband circularly polarized microstrip array antenna co-designed with a high-performance artificial magnetic conductor and frequency selective surface (AMC-FSS) radome. Compared with the absorbent frequency selective radome-based antenna, the proposed co-designed antenna can achieve a relatively low gain loss in an extremely wide frequency range with wideband in-band and out-of-band RCS reduction, due to the introduction of a novel AMC-FSS radome which can achieve low insertion loss and wideband transmission by combining a double-layer miniaturized bandpass FSS and a single-layer chessboard AMC surface. We demonstrate the effectiveness of the proposed AMC-FSS radome and co-designed antenna through simulations and measurements. The results show that the gain deterioration of the co-designed antenna is only 0.42 dB at the central frequency of 4.8 GHz and less than 1 dB in the wide frequency band, ranging from 4.23 to 5.38 GHz with a relative bandwidth of 23.9%. At the same time, the monostatic RCS for a normal incidence is greatly reduced from 4 to 18 GHz.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Interplanted Patch-Monopole Array With Enhanced Isolation

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      Authors: Yi-Feng Cheng;Jie Liu;Changning Wei;Wen-Jing Wu;Liguo Sun;Gaofeng Wang;
      Pages: 1664 - 1668
      Abstract: This letter proposes a novel interplanted patch-monopole array. The adjacent and nonadjacent isolations are significantly enhanced by manipulating two types of mutual couplings. The proposed array is simple in structure and can be easily extended to large scale linear arrays. The air-dielectric patch antenna with a slot has a wide bandwidth and compact size. Besides, the antenna array is mainly constructed using metal (no dielectric loss), so the radiation efficiency is very high. For verification, a four-element array with center-to-center spacing of 0.467 λ0 has been designed and prototyped. Simulation and experimental results show that the proposed array features compact layout, enhanced port isolation, high radiation efficiency, and good pattern diversity.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Single-Feed Multibeam Conformal Transmitarrays With Phase and Amplitude
           Modulations

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      Authors: Li-Zhao Song;Xuan Wang;Pei-Yuan Qin;
      Pages: 1669 - 1673
      Abstract: Single-feed multibeam conformal transmitarrays using a superposition method are presented in this letter. The arrays consist of ultrathin Huygens elements with independent amplitude and phase manipulations. Three cylindrical conformal transmitarrays with dual-beam radiation patterns are designed at 10 GHz, producing dual beams at ±30°, +30°, and −20°, +30° and −10°, respectively. As an experimental validation, the prototype with symmetrical dual beams is fabricated and measured. Two beams at +29° and −28° along the H-plane are achieved with a measured 18.29 dBi peak gain. The gain difference between the two beams is 0.13 dB. Good agreement between simulation and measurement is observed.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Maximum Gain of Array Antenna With Closely Placed Dipole Elements

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      Authors: Yoshio Karasawa;
      Pages: 1674 - 1677
      Abstract: A double integral operation is required to obtain gain in an array antenna in general, and only an omnidirectional antenna is represented in a closed form. In this letter, as a result of radio-wave propagation research, a closed-form expression that can be applied to a small dipole antenna or a half-wavelength dipole antenna is shown by using an equation applicable to spatial correlation in a three-dimensional multipath environment. In addition, the maximum gain characteristics of the half-wavelength dipole element linear array antenna are analyzed using the equation.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Theory and Experiment of Array Calibration via Real Steering Vector for
           High-Precision DOA Estimation

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      Authors: Peng Yang;Bei Hong;Wei Zhou;
      Pages: 1678 - 1682
      Abstract: Adaptive array calibration is a key technique, which significantly affects the performance of array signal processing in real environments. In this letter, we propose a general and simple method using real steering vectors (RSVs) for array calibration and high-precision direction of arrival estimation. The RSVs are constructed with the data sampled at intermediate frequency directly. All errors of the antennas and channels are taken into account. The effectiveness of this method is evaluated by simulation and measurement with a four elements microstrip linear array and a cylindrical conformal array. Both simulation and measurement results show that it is an efficient calibration method and is suitable for arrays with directional elements.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Pattern-Reconfigurable Liquid Metal Magneto-Electric Dipole Antenna

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      Authors: Xiong Geng;Ming Su;Yanming Zhang;Anna Wang;Chengkang Pan;Xiaochen Chen;Zheng Liu;
      Pages: 1683 - 1687
      Abstract: We propose a pattern-reconfigurable liquid metal magneto-electric dipole antenna. The antenna is composed of a magneto-electric dipole made of copper and a liquid metal channel structure made of Polycarbonate (PC), one Г-Type feeding strip is placed in the middle of magneto-electric dipole for coupling feeding. The proposed pattern-reconfigurable antenna mainly uses liquid metal to make parasitic units around the antenna. Each liquid metal parasitic unit is controlled separately and connected with the liquid storage tank at the bottom through a plastic tube, by changing the arrangement of parasitic units, the pattern reconfiguration of 15 states can be realized corresponding to (θ, Φ) max = (0°, 0°), (±32°, 0°), (±30°, ±30°), (±32°, ±58°), (±28°, ±86°). The main working frequency band of the antenna is 2–2.5 GHz. When the working state of the antenna changes, the gain is always higher than 6 dB and the efficiency is greater than 70%. The proposed antenna can cover part of the communication frequency band and can be used for future communication.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • A Wideband Frequency-Selective Rasorber With Rectangular Spiral Resonators

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      Authors: Qijun Xing;Weiwei Wu;Yuchen Yan;Ximeng Zhang;Naichang Yuan;
      Pages: 1688 - 1692
      Abstract: This letter presents a frequency selective absorber (FSR) with a passband and two wide absorption bands. The structure is composed of a resistive layer and a bandpass frequency selective surface (FSS) layer. The resistive layer is a combination of metal lines with loaded resistors and rectangular spiral resonators, which generate parallel resonances. Square slots are designed in the bandpass FSS to produce parallel resonance inside the passband and perform as a metal plane outside the passband. A nearly transparent window can be obtained by adjusting the parallel resonant frequencies of two layers to be consistent. The simulation results show that the 3 dB transmission band ranges from 6.5 to 7.76 GHz, and the minimum insertion loss is 0.05 dB at 7.09 GHz. The dual-polarized FSR presents stable operating characteristics and realizes two absorption bands on both sides of the passband, and the fractional bandwidth of the reflection coefficient lower than −10 dB is up to 127%, which ranges from 2.69 to 12.04 GHz. In addition, the FSR is manufactured and measured, and the measurement results are consistent with the simulation results.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Design and Implementation of a Quasi Nondiffraction Beam for Microwave
           Power Transmission Application

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      Authors: Hui Xiao;Huaiqing Zhang;Dongping Su;Jianyu Chen;Xinyuan Li;Han Xiong;Dongping Xiao;
      Pages: 1693 - 1697
      Abstract: In this letter, a quasi nondiffraction beam is designed and implemented for microwave power transmission (MPT) application. To generate a quasi nondiffraction beam, a new formula is derived to calculate the phase distribution on the metasurface (MS), and a phase shifting unit with 360° transmission phase coverage and transmission amplitude better than −3 dB is designed to achieve desired phase. The simulated and measured results demonstrate that a quasi nondiffraction beam can be generated by the proposed MS. In order to prove that the quasi-nondiffraction beam can be used for microwave power transfer, a miniaturized MPT system is built and measured. The system-level measurement results indicate that the proposed transmitting antenna helps the receiving terminal to harvest more power and improves the power transmission efficiency of the system.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Compact Dual-Polarized Filtenna With Steep Roll-Off Rate for Base Stations

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      Authors: Ji Wen Wang;Shuai Sun;Ruyu Ma;Xiu Yin Zhang;
      Pages: 1698 - 1702
      Abstract: This letter presents a dual-polarized, band-pass filtering antenna, or “filtenna” with a steep roll-off rate and a compact size. To simultaneously support multiple communication standards in a shared aperture, base station antenna arrays need to operate in multiple closely-spaced frequency bands. However, each filtenna has a limited space in the aperture-shared array; therefore, it is challenging to achieve a high roll-off rate. To resolve this problem, we proposed a filtenna that consists of four stacked X-shaped patches, of which the second from the bottom is the driven patch and the rest are parasitic ones. These closely coupled parasitic patches switch rapidly from resonance to antiresonance; however, their radiations change because they together cancel one another and create a very steep roll-off rate. The aperture dimension of the proposed antenna is $0.2 , lambda _{0} times 0.2 , lambda _{0} times 0.14 , lambda _{0}$, where $lambda _{0}$ is the wavelength in free space at the center frequency. The measurement results demonstrate a very steep roll-off rate up to 1795 dBi/GHz at the lower cutoff frequency of 1.8 GHz. The measured average gain was 8 dBi over the operating frequency band of 1.805–1.88 GHz, which makes the proposed filtenna a good candidate for multiband and multistandard base stations.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Phantom Design and Verification Enabling Effective Antennas for Bird
           Tracking Technology

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      Authors: Bryan A. Sandoval;Eli S. Bridge;Caleb F. Fulton;Jessica E. Ruyle;
      Pages: 1703 - 1707
      Abstract: Advances in miniaturized radio tracking technology are helping to revolutionize the field of wildlife biology, especially with respect to studies of small birds. However, development of antennas for animal tracking applications often fails to formally account for the effects of the animal’s body on signal transmission. This letter describes an electromagnetic phantom that accurately represents a small bird. The phantom is validated with empirical measurements and can be easily scaled to represent larger or smaller bird species.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Rapid Failure Diagnosis of Impaired Linear Antenna Arrays Based on Matrix
           Pencil Method

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      Authors: Guo Bai;Cheng Liao;Yuanzhi Liu;You-Feng Cheng;
      Pages: 1708 - 1712
      Abstract: In this letter, a modified matrix pencil method (MPM) is proposed and applied to the failure diagnosis of linear antenna arrays. By sampling the far-field pattern of the impaired array, and considering the locations and excitations of the failed elements as the poles and residues, a noniterative process based on MPM can quickly find the failed elements. The modified MPM can further screen the diagnostic failed elements and correct their estimated locations and excitations to make the diagnosis results more accurate. Numerical evaluation and comparison results demonstrate that the proposed method has good performance in calculation time and robustness to noise.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Comments on “Frequency Diverse Array Beampattern Synthesis With Taylor
           Windowed Frequency Offsets”

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      Authors: Zeeshan Ahmad;Zain ul Abidin Jaffri;Shu-Di Bao;Meng Chen;
      Pages: 1713 - 1714
      Abstract: In recent years, frequency diverse array (FDA) has been actively studied due to its extended capabilities over phased arrays [1]–[3]. Unlike phased arrays whose transmit elements radiate fixed frequencies and generate an angle-dependent beampattern, FDA applies an element-wise tiny incremental frequency shift to provide additional degrees-of-freedom in angle as well as in range dimension [4]–[6]. In a traditional FDA, the element-to-element incremental frequency offset applied is progressive, which results in a time-periodic and S-shaped range-angle coupled beampattern [1]–[6]. However, it is difficult to accurately estimate the target parameters in the presence of such range-angle ambiguity [6]. Consequently, various solutions have been proposed in an effort to avoid such ambiguity in the FDA beampattern. Among them, employing nonlinear frequency offsets, and using nonuniform array configuration are the two prominent solutions to achieve a decoupled range-angle-dependent beampattern [7], [8].
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
  • Reply to “Comments on ‘Frequency Diverse Array Beampattern Synthesis
           With Taylor Windowed Frequency Offsets”’

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      Authors: Hu Tang;Yi Liao;
      Pages: 1715 - 1716
      Abstract: We Would like to thank Ahmad et al. [1] for reading the letter [2] and providing some comments on the performance comparison of frequency diverse array (FDA) with different windowed types of frequency offsets, which is helpful for the FDA beamforming design.
      PubDate: Aug. 2022
      Issue No: Vol. 21, No. 8 (2022)
       
 
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