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An analysis of actual optical ray paths in flat gradient-index (GRIN) lenses for multifocal multi-beam radiations is introduced in this paper. The formulation is rigorously established using the conservation of momentum applied to an offset focal point for the extreme beam generation. Assisted by the above analysis, a new lens design approach for GRIN profile synthesis is proposed with two extreme focal points, and then extended to determine a convenient locus of feed that allows for covering the scanning range with minimal overall aperture phase errors. The ray-path errors have been tested and compared with those of previously reported multi-beam GRIN lenses, which were based on a straight, parallel ray-path assumption inside the lens. The superiority and generality of the new design formulas have been proven by comparing lens prototypes from the two different methods. It is demonstrated that the proposed one can enable consistent gain enhancement for multiple beams at different operating frequencies. Finally, the new design method has been validated by implementing an all-dielectric 3-D printed seven-beam flat GRIN lens. A wide beam coverage of ±44° has been realized with measured scanning losses between 1.2-2.93 dB at different frequencies. The measured 3-dB gain bandwidth is 42.8% covering 12.3-19 GHz.

In this work, we propose an integrated MIMO system which performs target tracking and downlink communications, as well as receiving uplink signals from other communication nodes to achieve bi-directional communications. The key to such a system is the constrained joint transmit waveform design, which constitutes the main contribution of this work. Per the practical requirement of waveform design, we introduce a new realistic power constraint, referred to as peak-to-valley-power-ratio control with energy budget (PVRC-EB), to remedy the shortcoming of the traditional energy constraint in terms of the transmit elemental power uniformity control. To realize the integrated function of radar and communication, we formulate two joint transmit waveform designs, which achieve a tradeoff between radar function and downlink communication subject to spectral or spatio-spectral energy constraints for accommodating simultaneous uplink communications. For the first design with only spectral constraint, we derive an efficient algorithm based on successive alternating projection (SAP), with its convergence theoretically being proved to approach a stationary point. For the second design with spatio-spectral constraints, we propose a method, referred to as SAP-ADMM, which incorporates the derived SAP steps into the framework of alternating direction method of multipliers. Numerical results demonstrate the effectiveness of the devised methods and a good balance among the three functions can be achieved.

This paper presents the development of a four-port in-band full-duplex (IBFD) antenna array system featuring a shared radiation aperture, utilizing a combination of common-mode (CM) and differential-mode (DM). The IBFD antenna system comprises two subarrays, with simultaneous excitation of any of the four input ports activating one subarray in CM and the other in DM. Incorporating both CM and DM in both the xoz and yoz planes results in identical radiation patterns when any of the four ports are stimulated. The proposed method is different with all existing method. It enables full aperture excitation in any of the four modes, markedly increasing gain without compromising beamwidth. Besides, it is less sensitive to the imbalances of the feeding components. To validate the proposed method, the IBFD antenna system is designed, fabricated, and measured. Experimental results confirm the effectiveness of the approach, showcasing isolation exceeding 38 dB between any two ports within the bandwidth of 3.3 - 3.8 GHz (14.1%). Additionally, each port of the system exhibits similar and broadside radiation patterns, underscoring the significant potential of this approach for IBFD systems in 5G sub-6 GHz applications.

The investigation of beamforming networks (BFNs) for multibeam antenna arrays has been ongoing for decades. However, enabling individually controllable multibeams employing a BFN has remained a recognizable challenge. The utilization of generalized joined coupler (GJC) matrices has demonstrated its efficacy as a viable solution for achieving multibeams with independent individual beam directions and minimal sidelobe levels. In this paper, for the first time, the design of the GJC matrix as a multibeam feeding network is reported using planar circuits and verified experimentally. The GJC matrix design is built based on a mixture of one-section and two-section branch-line couplers, which are able to realize a wide range of coupling coefficients. A thorough investigation from theoretical analysis to electromagnetic modeling is conducted on one-section and two-section branch-line couplers, and a general design guideline is given for choosing the appropriate type and dimensions for each coupler in a GJC matrix. Then, two types of BFN using microstrip line working at 5 GHz and stripline working at 12 GHz are designed, fabricated and measured, respectively. Different beam angles are realized to demonstrate the independent and simultaneous multibeam steering functionality, the experimental results agree well with the theoretical ones.

A new design method of gradient-index (GRIN) lenses is presented to obtain wide multi-beam coverage and high aperture efficiency. Multilayer metasurfaces using effective medium concept are deployed for the lens implementations. The radiation performance of the GRIN lens has been validated based on microstrip array illuminations. The design theory has been well verified with both simulation and measurement.

Cooperation can help unmanned aerial vehicles (UAVs) improve their plans to visit charging stations and avoid congestion, but can be hindered by privacy concerns. We propose a new, privacy preserving, joint routing, and charging scheduling framework which allows multiple cellular-connected UAVs to jointly optimize their routes and charging schedules in a decentralized fashion. The framework allows each UAV to minimize its energy usage and connectivity outage, maximize its recharged energy, ensure its timely arrival, and preserve its privacy concerning its trajectory and destination. The key idea is that we obfuscate probabilistically the destination of each UAV, and design a new noncooperative Bayesian game among the UAVs to find their best routes and charging schedules toward the obfuscated destinations. Another important aspect is that we prove the game is a potential Bayesian game with a pure-strategy Bayesian Nash equilibrium and the best response yielded with the Bellman-Ford algorithm. This new framework preserves the UAVs' privacy in the sense that an UAV only shares the probability of its visit to a charging station at different times, and its best response is based on an obfuscated destination. Simulations demonstrate that the framework ensures timely arrivals with near-optimal routes and substantially lower complexity than a centralized routing scheme based on brute force. 2168-2216

This paper presents an overview of the advances in reconfigurable Ygai Uda antenna for smart wireless communications systems In particularly it reports the development of planar Yagi Uda antenna with frequency and pattern reconfiguration Furthermore this paper presents a recent design on a circular array of Yagi Uda monopoles with a full 360 azimuthal beam scanning

This chapter introduces a recently conceived dual-function radar-communications (DFRC) system that exploits a frequency-hopping (FH) multiple-input and multiple-output (MIMO) radar to achieve a reasonably high-speed and long-distance data communication link. To promote the awareness and general understanding of the novel DFRC, its essential aspects, e.g. signal model and information embedding/demodulation, as well as some recent breakthroughs in timing and channel estimations are illustrated in detail.

This paper proposes an orthogonal expanded memory polynomial (OEMP) model for circular complex Gaussian processes. The basis functions of the OEMP model are constructed from those of the expanded memory polynomial (EMP) model recently derived by expanding the conventional memory polynomial (MP) model for I/Q imbalanced signals, and proved orthogonal to each other thanks to the derived closed-form bivariate distribution moments. In addition to the perfect duality with its power spectral density expression, the OEMP model also demonstrates unique minimum residual power property. It is believed that the OEMP model will be highly beneficial to nonlinearity mitigation for wideband wireless communication systems. Simulation and experimental results obtained from a terahertz system with 4.25 GHz bandwidth and 252 GHz carrier frequency confirm that significant performance improvement can be achieved for digital post-cancellation with low-complexity after applying the proposed OEMP model.

An iterative fast segmented cyclic convolution (IFSCC) method is presented for accurately and efficiently synthesizing the pattern of a uniformly spaced circular array (USCA) considering directive element patterns as well as mutual coupling. In this method, the transformations between the excitation vector and the USCA pattern are formulated as a fast segmented cyclic convolution (FSCC) and an inverse FSCC, which can be highly efficiently accomplished by using a fast Fourier transform (FFT) and an inverse FFT. The IFSCC method overcomes the limitation of FFT in synthesizing USCA patterns without interpolation or approximation processes. Numerical examples of synthesizing different USCA patterns are conducted to validate the effectiveness and efficiency of the proposed method. The synthesis results also demonstrate the advantages of the proposed method.

A novel three-layer substrate-integrated waveguide (SIW) 9times9 Butler matrix (BM) that can produce a broadside beam and wide-angle coverage is presented in this article. Unlike the traditional 8times8 BM, the proposed BM is realized by cascading three-way couplers. Connecting to the radiation structure and feeding the center input port, a phase difference of 0° is observed and a broadside beam can be produced. When exciting the side input ports, a maximum phase difference of ±160° is obtained and wide-angle side beams are generated. The operation principle and design development of the 9times9 BM are illustrated in detail to determine the topology and the phase shifters. With the desired phase differences and amplitude distributions, a three-layer topology of the 9times9 BM is developed to reduce the footprint and improve the compactness, which is subsequently realized in SIW technology. To realize wide-angle coverage, a new endfire metasurface antenna derived from the traditional Vivaldi antenna is proposed, which achieves a fractional 10-dB impedance bandwidth of 72% and a half-power beamwidth (HPBW) of 128° at 28 GHz. By integrating the three-layer SIW 9times9 BM with an endfire metasurface antenna array, a wide-angle endfire multibeam metasurface antenna is obtained, which achieves a wide HPBW coverage of ±113° and a maximum gain of 12.1 dBi. The topology of an extended single-layer 18times18 BM based on the designed 9times9 BM is presented, and multilayer solutions are adopted to demonstrate the possibility of realizing higher order BMs.

Bi-static sensing is crucial for exploring the potential of networked sensing capabilities in integrated sensing and communications (ISAC). However, it suffers from the challenging clock asynchronism issue. CSI ratio-based sensing is an effective means to address the issue. Its performance bounds, particular for Doppler sensing, have not been fully understood yet. This work endeavors to fill the research gap. Focusing on a single dynamic path in high-SNR scenarios, we derive the closed-form Cramér-Rao bounds (CRB). Then, through analyzing the mutual interference between dynamic and static paths, we simplify the CRB results by deriving close approximations, further unveiling new insights of the impact of numerous physical parameters on Doppler sensing. Extensive simulation results are provided to validate the preciseness of the derived CRB results and analyses, with the aid of the maximum-likelihood estimator.

Wideband millimeter wave and terahertz systems face severe nonlinearity and other practical impairments such as transmitter and receiver in-phase/quadrature imbalances (IQIs), carrier frequency offset, and phase noise. Based on a simplified yet effective received signal model including an expanded memory polynomial (EMP) and a noisy receiver filter, this paper proposes a low-complexity digital post-cancellation (DPC) framework for transmitter IQI and overall system nonlinearity mitigation. The nonlinearity parameters with reduced nonlinearity order are firstly estimated with low-complexity using a novel transmission protocol incorporating both frame rotation and preamble power scaling. Through widely linear system equalization and interference cancellation, the signal distortion caused by frequency-dependent IQI and nonlinearity is then mitigated with significant performance improvement. The mean-squared-error measurement of the EMP-modelled signals also provides a practical means for the nonlinear system identification and characterization. Both simulation and experiment results obtained from a millimeter wave system with 2.125 GHz bandwidth and 73.5 GHz carrier frequency are presented to verify the theoretical analyses and demonstrate the effectiveness of the DPC technology.

The strong cross-band scattering in dual-band base station arrays can cause degraded antenna performance, affecting the radiation performance of the antenna working in higher frequencies. This paper presents a filtered bowl-shaped low-band (LB) antenna covering 0.80-0.96 GHz for dual-band base station arrays, featuring effective wideband cross-band de-scattering capability in the high-band (HB). By incorporating specially designed helical filters into the LB radiators, a significant de-scattering HB bandwidth reaching 66.7% (1.36-2.72 GHz) of the LB antenna is achieved. To improve the LB impedance matching, specialized LC circuits are incorporated into the LB balun. These LC circuits, in conjunction with the baffles, also serve to ease the gain fluctuations of the HB antenna placed inside the LB antenna. In addition, the miniaturized aperture size of the LB antenna facilitates enhanced in-band isolation in the array. The LB antenna’s structural stability is guaranteed by the 3D-printed T-shaped dielectric supports. The measurement results of the fabricated dual-band array agree with the simulations, which validates the efficacy of this design.

This article presents a reconfigurable millimeter-wave (mm-wave) dual-polarized antenna array system featuring wide-range continuous beamwidth control (WCBC) using the polarization-mixing method. By simultaneously exciting dual polarizations, the system achieves wider beams, with a continuously adjustable beamwidth ranging from 21° to 100°. Additionally, the system retains its original beam scanning capabilities when using the two polarizations separately. Importantly, the ability in flexible beam scanning and wide beamwidth tuning is accomplished with only phase shifters without the need for amplitude control. All antenna elements are fully excited, ensuring high overall efficiency. The robustness and stability of the system are confirmed through error analysis. The WCBC array system is designed, fabricated, and experimentally validated. By employing a control circuit, it realizes reconfigurable dual functionality, i.e., beam scanning and wide beamwidth variation, in a simple and cost-effective manner.

Analogue multibeam antennas are poised to become a major technology for 6G In this talk we present an overview on circuit type multibeam antennas and present a new type of feed networks for multibeam antennas known as the generalized joined coupler GJC matrix A salient feature of the GJC matrix is that the same phase shifters can be used for tuning each beam and different beams can be steered continuously and independently Different configurations of the GJC matrix and the different theories for designing the GJC matrix are discussed Some implementations issues and new experimental results will be reported

This paper introduces holistic approaches to address the challenges faced by a typical dual band side by side antenna array arrangement where antennas with close spacing suffer from significant interactions leading to degradation in radiation patterns and port to port isolations The proposed methods utilize three multifunctional loading structures including a 2 5 dimensional 2 5 D cloak defected ground structure DGS and resonance shifter RS to simultaneously suppress both cross band scattering and coupling These structures effectively mitigate the cross band interactions between the low band LB and high band HB antennas Moreover the 2 5 D cloak and RS also contribute to in band coupling suppression and improved isolation between adjacent HB antennas In addition all these structures can be designed on the same substrate as the original antennas eliminating the need for additional layers This feature not only ensures cost effectiveness but also facilitates the implementation process making it easy to integrate the proposed techniques into existing antenna systems

Joint communications and sensing (JCAS) have the potential to improve the overall energy, cost and frequency efficiency of Internet of Things (IoT) systems. As a first effort, we propose to optimize the MIMO-OFDM data symbols carried by subcarriers (SCs) for better time- and spatial-domain signal orthogonality. This can reduce intertarget and interantenna interference, enabling high-quality sensing. We establish an optimization problem that modifies data symbols on SCs to enhance the above-mentioned signal orthogonality. We also develop an efficient algorithm to solve the problem based on the majorization-minimization framework. Moreover, we discover unique signal structures and features from the newly modeled problem, which substantially reduce the complexity of majorizing the objective function. We also develop new projectors to enforce the feasibility of the obtained solution. Simulations show that to achieve the same sensing performance, the optimized waveform can reduce the signal-to-noise ratio (SNR) requirement by 3-4.5 dB compared with the original waveform, while the SNR loss for the uncoded bit error rate is only 1-1.5 dB.

A new method to achieve wideband conformal transmitarrays is presented by employing tightly coupled Huygens element in this paper. The element is composed of five pairs of metallic strips which are printed on two sides of a dielectric substrate. The tightly coupled elements can achieve a high transmission and a nearly full phase coverage in a wide bandwidth from 71 to 87 GHz. To further analyze the element, equivalent circuit models are developed. Good agreement is achieved between circuit and full-wave simulations. A cylindrical conformal transmitarray at 78 GHz is designed, fabricated and measured. The measured results have good agreement with the simulated ones. The measured peak realized gain is 26.6 dBi with an aperture efficiency of 37.2%. The measured 3-dB gain bandwidth is 20.4% from 71 to 87 GHz, which can fully cover the E-band spectrum.

In this article, a wideband conformal transmitarray employing dual-layer tightly coupled Huygens elements is proposed at E-band. The element consists of five pairs of partly overlapped metallic strips with different lengths printed on two sides of a dielectric substrate. It can support tightly coupled Huygens resonances with a high transmission efficiency and a nearly full phase coverage in a wide bandwidth from 71 to 87 GHz. Equivalent circuit models are created to analyze the tightly coupled Huygens element, which has good agreement with that from full-wave simulations. In order to validate the proposed element, a cylindrically conformal transmitarray at 78 GHz is designed, fabricated, and measured. Good agreement between the measured and simulated results has been obtained, showing a peak realized gain of 26.6 dBi with an aperture efficiency of 37.2% from measurement. A measured 3 dB gain bandwidth of 20.4% is achieved from 71 to 87 GHz, fully covering the E-band spectrum.

Modulated metasurface is considered as a good candidate for low profile multi beam antennas Usually a superposition method of all impedance modulations for different beams is used However a limitation of this method is that a very small number of beams can be generated due to the mutual interference of different impedance modulations which will lead to low gains and high side lobe levels It is found that the source locations for each beam play a key role in interference suppression In this paper instead of using the time consuming full wave simulation based optimization the optimal source locations are obtained by using the aperture fields calculated from the zeroth order approximation of the currents on the surface To verify the design concept a five beam modulated metasurface antenna has been designed fabricated and measured providing an angular coverage up to 30 Good agreement between the simulation and measurement has been obtained

Multi beam conformal transmitarrays with a single feed antenna are synthesized using two different methods for the first time First a particle swarm optimization PSO algorithm is employed for phase only optimizations on a cylindrical transmitting surface producing a two beam radiation pattern at 30 in the circular cutting plane Second a superposition method is investigated to achieve the same objective showing a higher peak gain and lower sidelobe levels compared to the results from PSO Third the superposition method is further analyzed for a single feed quad beam conformal transmitarray As a proof of concept the prototype designed using the superposition method for two beams is manufactured and tested Good radiation performance is observed with two beams at 29 and 28 respectively The peak measured gain is 18 3 dBi and the gain difference of two beams is only 0 1 dB

Linearly polarized (LP) multiport multibeam antennas (MBAs) based on modulated metasurface (MTS) are presented in this article. A key challenge for MTS to generate multiple independent beams is the mutual interference of different impedance modulations. This interference can lead to reduced directivities of main beams and high sidelobe levels (SLLs). A full-wave-based optimization for a large number of beams is significantly time-consuming and practically ineffective. The source locations are optimized here by employing the aperture field calculated from a zeroth-order approximation (ZOA) of the currents on the surface. This provides a good preliminary accuracy without any full-wave analysis. The relevant design method is verified by two examples of three-beam and seven-beam MTS antennas. Furthermore, the seven-beam MTS antenna is fabricated and successfully measured. The measurements show a measured realized gain of 20 dBi at 14.10 GHz with a beam coverage (10-dB overlap) up to ±36°. It is seen that the same performance requires larger areas with conventional summation of apertures.

In this manuscript, broadband transmitting metasurfaces are developed to enhance frequency-dependent beam scanning. A triple-gold-layer unit cell is designed for wideband transmissions with low losses and quasi-linear phase variations. Comprehensive analyses of phase-gradient metasurfaces are provided to enable high-efficiency and wide-angle frequency scanning. For verifications, two metasurfaces with different phase gradients are simulated, manufactured, and measured. Continuous beam scanning performance has been demonstrated successfully from 80 GHz to 220 GHz, showing beam scanning ranges of 25° and 31.5° from two prototypes, respectively. Peak transmission efficiencies of 84% and 75% have been obtained from experiments. The results from simulation and measurement agree very well. The developed metasurfaces have many potential applications such as frequency-scanning terahertz (THz) imaging.

A beam steering transmitarray utilizing reconfigurable dual layer unit cells is presented in this paper Two PIN diodes are used on each array unit cell to achieve a 1 bit phase change with a high transmission Compared to other electronically reconfigurable transmitarrays employing multilayer unit cells with metal vias the developed transmitarray has a much simpler configuration which is beneficial to larger aperture designs in high frequency bands To validate the unit cell design concept a transmitarray prototype at 13 GHz is designed The measured peak gain is 18 4 dBi and 2 D beam steering performances are 50 and 40 in E and H planes respectively

Joint communications and sensing (JCAS) is potentially a hallmark technology for the sixth generation mobile network (6G). Most existing JCAS designs are based on digital arrays, analog arrays with tunable phase shifters, or hybrid arrays, which are effective but are generally complicated to design and power inefficient. This article introduces the energyefficient and easy-to-design multi-beam antenna arrays (MBAAs) for JCAS. Using pre-designed and fixed analog devices, such as lens or Butler matrix, MBAA can simultaneously steer multiple beams yet with negligible power consumption compared with other techniques. Moreover, MBAAs enable flexible beam synthesis, accurate angle-of-arrival estimation, and easy handling/ utilization of the beam squint effect. All these features have not been well captured by the JACS community yet. To promote the awareness of them, we intuitively illustrate them and also exploit them for constructing a multi-beam JCAS framework. Finally, the challenges and opportunities are discussed to foster the development of green JCAS systems.

Currently, there is increasing interest in analog multibeam antennas whose beams can be flexibly steered to arbitrary directions. In a previous paper, we presented the theoretical framework for synthesizing individually steerable multiple beams using generalized joined coupler (GJC) matrices. The synthesis method was to optimize the array excitation vectors to approximate known distributions. In this article, we present a more robust optimization method to optimize the multibeams directly in order to control the half-power beamwidth, the sidelobe levels, and nulls for mitigating system interference. The effectiveness of the proposed method is demonstrated by numerical examples. We reveal how the quality of the multiple beams is inherently determined by the dimensions of the GJC matrix. Experimental results of a 3 10 Nolen-like GJC matrix are presented for the first time to validate the proposed method in realizing low sidelobe multibeams.

Beam alignment is a process for receive and transmit antenna arrays to find the correct beamforming directions. It is typically based on beam scanning and peak-energy searching, which lead to time-consuming beam training process in communication protocols, such as 802.11ad for vehicular networks. In this correspondence, we propose a fast beam alignment method for analog arrays, based on directly estimating the angle-of-arrival (AoA) of the incoming signals. We propose simple and highly efficient AoA estimators, by approximating the power of the array response as a Gaussian function. One estimator is based on the power ratio and can coherently combine multiple measurements scanned at arbitrary intervals and with different beam widths. The other two are based on an innovative idea of Gaussian curve fitting with weighted least square techniques, and one of them can even work without knowing the beam width. Simulation results validate the effectiveness of the proposed scheme.

This work generalizes the alternating projection approach (APA) to synthesize wideband frequency-invariant (FI) beam patterns for linear nonuniformly spaced arrays (NUSAs). Different from the conventional APA where excitation weights are synthesized for a desired pattern at single frequency, the generalized APA intends to find appropriate finite-impulse response (FIR) filter coefficients for each antenna element to provide the required wideband frequency-dependent excitation for a desired wideband FI pattern, and two modification techniques called mainlobe FI modification and wideband sidelobe control are introduced in each iteration to successively update the FI pattern performance. Several examples for synthesizing wideband FI beam patterns for NUSAs in different applications are conducted to verify the effectiveness and advantages of the proposed generalized APA.

When two antennas working in different frequency bands are placed in proximity, they suffer from strong cross-band interactions that degrade their radiation performance and reduce the isolation between them. This article presents holistic methods to simultaneously suppress cross-band scattering and coupling. Specifically, we develop a systematic solution to suppress the scattering of low-band (LB) antennas to high-band (HB) radiation as well as the scattering of HB antennas to LB radiation using three new techniques. This leads to much reduced cross-band coupling between the LB and HB antennas. The proposed methods are applied to a 'one LB + one HB' dual-band array configuration with only one LB cross dipole and one HB cross dipole placed side-by-side to exclude the effects of the array topology. The robustness of the proposed methods is comprehensively verified for different scenarios by simulations and experiments. Furthermore, the methods are evaluated in a 'one LB + four HB' array configuration. In addition to effectively suppressing cross-band scattering and coupling, the proposed methods also demonstrated a significant reduction in in-band coupling between adjacent HB antennas.

In this paper we present a new type of feed networks to feed multibeam antennas known as the generalized joined coupler GJC matrix Using the GJC matrix the same phase shifters for each beam can be tuned simultaneously to steer each beam independently The configuration of the GJC matrices the theory for synthesizing them and experimental results are reported

An in band full duplex IBFD antenna system having four ports with good self interference cancellation SIC is presented in this paper Two of the four ports provide 45 degree polarized radiation and the other two generate 45 degree polarized radiation To achieve high isolation between any two of the four ports three types of coupling need to be suppressed simultaneously which are the cross polarization coupling between the two ports of the same antenna the copolarization coupling between adjacent antennas and the cross polarization coupling between adjacent antennas The three types of couplings are defined as A type B type and C type coupling respectively In this work a novel isolation feed network is firstly proposed to deal with A coupling The isolation feed network also can differentially feed the antenna and achieve 45 degree polarizations without rotating the antenna Then the B and C couplings are also well suppressed in a double antenna system thanks to the extra defected ground structure DGS cross shaped walls and metal baffles The resultant isolation between any two of the four ports is 39 dB from 3 3 to 3 9 GHz The radiation patterns obtained by exciting the four ports are very similar to each other and are stable with frequency which makes the proposed antenna an excellent candidate for 5G sub 6 GHz IBFD applications

Integrating sensing into wifi platforms referred to as wifi sensing provides an efficient and device free means for indoor monitoring localization with low cost Clock asynchrony is one of the most challenging issues in wifi sensing A mainstream solution to date employs cross antenna processing to suppress the clock offsets that are common to all antennas Such methods however may suffer from issues such as mirrored targets and noise enhancement etc This paper develops a novel wifi sensing scheme It embodies accurate and low complexity methods for estimating the timing and frequency offsets as well as the angle of arrival AoA all from the LoS path It also involves a coherent Doppler processing method which effectively suppresses static paths and accurately estimates the Doppler by enjoying the coherent processing gain Corroborated by experimental results using open Widar2 0 data the proposed design is able to precisely recover the velocity traces in various indoor scenarios

In-band full duplex (IBFD) communication has garnered significant attention due to its potential to enhance spectrum efficiency. In contrast to traditional two-port IBFD systems, four-port configurations offer advantages like increased diversity gain and channel capacity. However, achieving effective four-port systems is challenging due to various forms of self-interference. This paper presents an overview of two IBFD antenna systems featuring four isolated ports, outlining their operational principles and configurations. Performance analysis underscores the suitability of both systems for IBFD applications.

In this paper a lightweight spherical Luneburg lens with high performance is introduced for use in the frequency range 1 FR1 The continuously varying refractive index profile of the lens is implemented using a quasi isotropic partially metalized periodic structure Much of the lens volume is made of foam so the design is lightweight making it applicable for low band microwave frequency communication systems and more specifically 5G communications in FR1 The periodic structure allows a simple and low cost layered construction with a quasi isotropic response This approach improves the scanning performance of the lens in all angular directions when compared to equivalent lens designs previously reported Such a structure is an ideal candidate for high gain multi beam communication systems

Analogue circuits for forming multibeams can be employed in integrated communications and sensing ICAS systems to save energy consumption and cost These circuits are in the form of matrices The most well known analogue circuit for multibeams is the Butler matrix However the Butler matrix has severe limitations it can only generate fixed beams with the number of beams as a power of two In this paper we present a new type of circuit matrix to form multiple beams which is referred to as the generalised joined coupler GJC matrix The GJC matrix can produce independently steerable multibeams as well as any number of orthogonal beams The beams can be shaped to produce low sidelobes and deep nulls to mitigate the mutual interference between the communications and sensing beams These unique features and their applications to ICAS are demonstrated in the paper

Analog beamforming for multibeam antennas is envisioned as a key enabling technology for next-generation mobile communications and sensing networks. Whilst many existing analog multibeam antennas have limited beam forming and steering capabilities, a recently developed generalized joined coupler (GJC) matrix makes it possible to form multiple beams in any direction and steer them independently by tuning the phase shifters. In this work, we propose a novel design method for the GJC matrix by jointly designing both the directional couplers and phase shifters instead of the published coupler-only optimization, thus significantly enhancing the beamforming performance of the GJC matrix. To this end, we derive deterministic solutions to solve the parameters of the directional couplers and phase shifter values beam-by-beam. Specifically, we present algorithms to design Blass-like and Nolen-like GJC matrices. It is further shown that the derived solutions are exact for a full-dimensional Nolen-like GJC matrix to generate orthogonal beams of any dimension. Based on the theoretical analysis, we propose an improved architecture for implementing the GJC matrix. Extensive simulation and numerical results are provided to validate the high performance of the proposed designs and their superiority over the prior art in various low-sidelobe beamforming and beam steering scenarios.

This paper introduces a polarization-mixing strategy to significantly widen the beamwidth of a typical ±45°-polarized base station antenna array. Without changing the array topology, the originally narrow beamwidth of the array is significantly enhanced by mixing the two orthogonally polarized radiations. Compared to the traditional pattern synthesis methods, the proposed method can have much wider beamwidth and does not need amplitude weighting. The polarization-mixing method leads to a spatially-variable-polarization (SVP), i.e., the array has different polarizations at different directions. To guarantee the polarization diversity requested in modern wireless communications, two SVP arrays with orthogonal polarizations are designed.