Large Antenna Arrays Research Articles

Non-Volatile RF Reconfigurable Antenna on Flexible Substrate for Wireless IoT Applications

To date semiconductor switches are still the main enablers for electrical circuit and system reconfigurability. They however not only consume dynamic power but also dissipate static power, the former for performing on/off operation and latter for holding on/off state. These semiconductor devices are volatile and not energy efficient due to the need for holding voltage and can significantly increase the system power consumption where hundreds and thousands of switches are needed, such as in large reconfigurable intelligent surfaces and large antenna arrays. In this work, we report a non-volatile reconfigurable antenna that can switch between dual-band at 2.4 GHz and 5 GHz to a single band at 3 GHz. The measured results including reflection, gain and radiation patterns reveal promising performance, experimentally demonstrating a new approach of design and realization of RF switch integrated multi-band reconfigurable antennas. This zero-static power mechanism, along with easy fabrication on the flexible substrates would be very beneficial for Internet of Things (IoT) applications.

The Interference Channel Revisited: Aligning Interference by Adjusting Antenna Separation

It is shown that, in a line-of-sight setting, a receiver equipped with two antennas may approximately null an arbitrary large number of spatial directions to any desired degree, while maintaining the interference-free signal-to-noise ratio, by judiciously adjusting the distance between the antenna elements, provided that the spacing can be made sufficiently large. The main theoretical result builds on ergodic theory. The practicality of the scheme at moderate signal-to-noise values is demonstrated for a scenario where each transmitter is equipped with a single antenna and each receiver has two receive chains and where the desired spacing between antenna elements is achieved by selecting the appropriate antennas from a large enough linear antenna array. We further extend the proposed scheme to show that interference can be nearly eliminated also in specular multipath channels as well as multiple-input multiple-output interference channels where a single additional receive antenna suffices to approximately align all interferers into a one-dimensional subspace. To demonstrate the performance of the scheme, we show significant gains for interference channels with four as well as six users, at low to moderate signal-to-noise ratios ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0\text{--}20$</tex-math></inline-formula> dB). The robustness of the proposed technique to small channel estimation errors is also explored.

Use of graphics processors to cardinally acceleration the calculation procedure of large subaperture active phased antenna arrays radiation pattern

For traditional APAA with a rectangular and triangular grid of nodes, in which partial emitters are installed, simple analytical formulas are known that express the dependence of the array radiation pattern (ARP) on the angular coordinates. If the grid of nodes is irregular, or in a regular grid there are failures of individual digits in the control elements (phase shifters, attenuators, delay lines) or in power amplifiers, then these formulas are not applicable. Therefore, it is necessary to address to general relations of additive summation of the specific contribution to the ARP of the field generated by each emitter separately. In large arrays, their number can range from several to many tens or even hundreds of thousands. Further, if it is necessary to synthesize a given type of array RP, it is necessary to form special types of the amplitude-phase distribution of the signal on the emitters. The procedures for synthesizing such distributions require hundreds or even thousands of repeated calculations of the array RP, which may require several million angular points to analyze in the upper hemisphere of radiation. The article shows that using parallel computing with the help of programming technology on graphics processors (GPU), produced by NVIDIA and CUDA technology in a system designed to quickly create high-performance codes in the extended C language, C++ is able to speed up the calculations of the large antenna ARP by 2…3 orders of magnitude, even on standard office computers. When using modern CPUs (AMD Ryzen Threadripper PRO 3995 WX) and GPU (NVIDIA GeForce 3090), the acceleration in calculations can additionally increase by hundreds of times. At such computing speeds, even the problems of antenna synthesis and statistical analysis of the characteristics of the array RP will be solved almost in real time. An example of a statistical estimation of the ARP parameters of a large subaperture array with 1280 emitters, used in the COSMOSkyMed system, when random failures of the inverse type occur in the phase shifter digits. The use of graphics processors allows us to solve problems such as the synthesis of an array RP having a prescribed shape, and the statistical analysis of the characteristics of the array in the event of various failure options in its elements, as well as mechanical distortions of the aperture shape, in almost real time.

A novel low-RCS antenna array based on integration of electromagnetic metasurface and conventional antenna

Aiming at obtaining low scattering antenna array, in this paper a novel method of integrating electromagnetic metasurface with conventional antenna is proposed. The theoretical analysis and practical implementation of this method are presented. Using this method, a novel antenna array is obtained by connecting partial unit cells of metasurface with transmission line and adopting coaxial excitations. In the radiation mode, the metasurface is excited and radiates effectively. Besides, the array has almost the same performance as the conventional array. In the scattering mode, this array demonstrates low in-band RCS due to the scattering cancellation of middle metasurface and other surrounding structures. Using this method, a 2 × 1 array, as an example, is designed and numerically analyzed. The results show that the array has the well-behaved radiation performance and low RCS property. The working principle of the proposed array is illustrated by investigating the current and resultant field. Further analysis also reveals the effecting law of metasurface unit cells in antenna's radiation and scattering performance. Therefore, flexible designs can be obtained to fit different requirements. Finally, experiments are conducted. And the good agreement between computations and measurements further verifies the validity of the proposed design. Moreover, the proposed method also features easy implementation and high integrity and can be extended to the designing of large scale array antennas.

Interleaved Parasitic Arrays Antenna (IPAA) for Active VSWR Mitigation in Large Phased Array Antennas With Wide-Angle Scanning Capacities

This paper explores a new concept for the design of high scanning-range phased array antennas: the Interleaved Parasitic Arrays Antenna or IPAA. In this concept, we use periodic parasitic elements and the generator impedance to control the Active Voltage Standing Wave Ratio (AVSWR) over a wide scanning range. This new array architecture comes with a design methodology enabling a smooth step-by-step design process aiming at reducing the need for full-wave calculations. First, a numerical dual-polarization design is presented in detail to illustrate the methodology and to give the design keys to the reader. Then, a prototype working in the 5G C-band between 3.4 and 3.8 GHz (11% bandwidth) was designed using this methodology and measured for a 36-element array. It is meant to demonstrate and validate the mutual coupling management done by the interleaved parasitic arrays and the design process accuracy. Good correspondence between measurements and simulation was found and the proposed unit cell with its corresponding tile can be integrated in a larger phased array with active modules to perform beam steering over an important scanning range without deteriorating the AVSWR. The proposed unit cell is designed for a high-scanning range going from $\theta =0^{\circ }$ to $\theta = 70^{\circ }$ for every $\varphi $ -directions and shows an active reflection coefficient for an infinite array below −13.6dB.

Bayesian Channel Estimation in Multi-User Massive MIMO With Extremely Large Antenna Array

We investigate wideband uplink channel estimation for a multi-user (MU) multiple-input single-output (MISO) OFDM system, in which the base station (BS) is equipped with an extremely large antenna array (ELAA). The existing compressive sensing massive multiple-input multiple-output (MIMO) channel estimation approach with a traditional sparsity promoting prior model becomes invalid in the ELAA scenario due to the spatial non-stationary effects caused by the spherical wavefront and visibility region (VR) issue. We therefore propose a new structured prior with the Hidden Markov Model (HMM) to promote the structured sparsity of the spatial non-stationary ELAA channel. Based on this, a Bayesian inference problem on the posterior of the ELAA channel coefficients is formulated. In addition, we propose the turbo orthogonal approximate message passing (Turbo-OAMP) algorithm to achieve a low-complexity channel estimation. Comprehensive simulations verify that the proposed algorithm has supreme performance under spatial non-stationary ELAA channels compared to various state-of-the-art baselines.

On the Achievable Rate Under Finite Codelength for RIS-Aided Systems

The ideal Shannon channel capacity can only be achieved by infinite codelength, so it is not accurate for practical finite codelength. The codelength of channel coding schemes heavily affects the performance of communication systems, but it cannot be too long to ensure affordable decoding complexity and latency. Unfortunately, existing performance analysis for systems aided by reconfigurable intelligent surface (RIS) only focus on the ideal channel capacity and neglect the achievable rate loss caused by finite codelength. To fill in this gap, this paper analyzes the achievable rate under finite codelength in a time-coherent RIS-aided systems, and gives an approximate analytic solution based on Taylor expansion and multi-dimensional central limit theorem. To be more specific, the closed form approximated achievable rate is given based on Taylor expansion, and it is shown that the required codelength decreases superlinearly with the increase of the number of RIS elements. Simulation results verify the analysis, and demonstrate the advantage of RIS-aided systems over the traditional large antenna array schemes.

Analysis of Intersymbol Interference Characterized by the Large Array Antennas Adopted in a 60-GHz-Band Gigabit Compact-Range Wireless Access System

A compact-range wireless access system in the 60-GHz band has been proposed for multi-Gb/s data transfer. A prototype Gigabit Access Transponder Equipment (GATE) was built to evaluate the system performance in terms of received signal strength, signal-to-noise ratio (SNR), and bit error rate (BER). The proposed system operates in the near-field regions of large array antennas adopted in the transmitter (Tx). The time delays due to the signals transmitted from different array elements to the receiver (Rx), or/and those due to the multiple reflections between Tx and Rx antennas become comparable with the symbol lengths in our gigabit wireless access system. In that sense, this system would be susceptible to intersymbol interference (ISI). In this study, the concept of ISI is introduced in the antenna field for the first time. An equivalent baseband communication system is newly proposed to evaluate the wireless channel, including Tx and Rx antennas. The analysis procedures and equations are provided for the calculation of ISI. The ISIs due to three potential contributions are analyzed in detail. It is verified that our proposed ISI analysis has succeeded in relating the antenna characteristic to the system performance observed in the baseband.

A novel hybrid IWO and CS algorithm for phase-only pattern synthesis of large array antenna

In this paper, a novel hybrid Invasive Weed Optimization (IWO) and Cuckoo Search (CS) algorithm (IWO/CS) is presented for phase-only pattern synthesis of large array antenna. The hybrid IWO/CS algorithm embeds the Levy flight of CS algorithm into IWO algorithm as a global guide, thereby enhancing the global search ability of the algorithm. At the same time, in order to avoid trapping into the local optimal solution, mutation operator is introduced to enhance search ability of the algorithm. Finally, competitive exclusion operation is improved to maintain the diversity of population. The hybrid algorithm is applied to phase-only beam shaping to achieve main lobe broadening and side lobe depression. Simulation results demonstrate the superiority of the hybrid IWO and CS algorithm.

A Wide Scanning Array of Connected Bowtie Antennas Suitable for Integration in Composite Sandwich Structures With Monte-Carlo Tolerance Analysis

A low-profile and wide-scan phased-array antenna of connected cross-bowtie elements is proposed. The design goals and considerations are based on the applications requiring the integration of a large array antenna with composite sandwich structures, such as antennas on aircraft. In a very large array environment (modelled approximately as an infinite array), the main beam of the proposed antenna can be steered up to ±75° at azimuth and ±15° at elevation over bandwidths of 10% and 25% with active reflection coefficients below −10 dB and −5 dB, respectively. A Monte Carlo analysis of critical manufacturing and alignment tolerances shows the desired performance is achieved with the cumulative distribution probability over 80% under the uniformly distributed random combinations of the tolerances. Experimental results of a $7\times 7$ element array prototype agree well with the simulations of this small-scale array case. The experiments show that this small-scale prototype is capable of steering the beam within the range of [−60°, 60°] at azimuth and [−15°, 15°] at elevation with the predicted performance satisfying the targeted application requirements and mechanical constraints. The achieved combination of the wide beam steering performance, relatively low antenna profile, and suitability of its feeding structure for sandwiched electro-mechanical integration makes this design unique with respect to the previously published results.

Spatial Interference Reduction by Subarray Stacking in Large Two-Dimensional Antenna Arrays

This article proposes a systematic approach for stacking uniform linear arrays (ULAs) of different sizes to reduce sidelobes and form nulls to the radiated beam pattern. In sidelobe reduction, the nulls and sidelobes of the vertically stacked ULAs are aligned to reduce the overall sidelobe level (SLL). In nulling, the nulls of varying length ULAs are aligned to configure the null direction and simultaneously reduce the sidelobes. Both approaches are relaxed to ensure the feasibility of the implementation. The stacking methods are studied by an extensive set of simulations together with azimuth and elevation beamforming. A sidelobe reduction method showed potential for better than 30 dB SLL and more than 20 dB relative null depth with less than 100 antenna elements. Finally, the concepts are validated by beam pattern measurements of a 28 GHz 64-element, 16-chain phased-array transceiver using a 100 MHz wide 5G waveform.

An Efficient Parallel Hybrid Method of FEM-MLFMA for Electromagnetic Radiation and Scattering Analysis of Separated Objects

In order to meet the rapidly increasing demand for accurate and efficient analysis of complex radiating or scattering structures in the presence of electrically large objects, a finite element method (FEM)-multilevel fast multipole algorithm (MLFMA) hybrid method that based on the Finite Element-Iterative Integral Equation Evaluation (FE-IIEE) mesh truncation technique is proposed in this paper. The present method makes use of FEM for the regions with small and complex features and MLFMA for the analysis of the electrically large objects, which ensure the accuracy and applicability of the method are better than most commonly adopted FEM-high frequency technique (HFT) hybrid method. The mutual interactions between regions are taken into account in a fully coupled way through iterative near filed computation process. In order to achieve an excellent performance, both algorithms have been implemented together from scratch, being able to run over multi CPU cores. An efficient parallel FEM domain decomposition method (DDM) solver with exploiting geometrical repetitions is included to drastically reduce memory requirements and computational time in the calculation of large array antenna. Also, the parallel MLFMA is adopted to expedite the near-field information exchange between regions. Through numerical example, the effect of distance between regions on the convergence of the proposed hybrid method is studied, and it is shown that the proposed method converge well even if the distance is equal to 0.05λ. Through comparisons with an in-house higher order method of moments (HOMoM) code and commercial software FEKO, the accuracy and effectiveness of the implemented parallel hybrid method are validated showing excellent performance.

Radio Localization and Mapping With Reconfigurable Intelligent Surfaces: Challenges, Opportunities, and Research Directions

5G radio for millimeter-wave (mm-wave) and beyond5G concepts at 0.1-1 THz can exploit angle and delay measurements for localization through an increased bandwidth and large antenna arrays, but they are limited in terms of blockage caused by obstacles. Reconfigurable intelligent surfaces (RISs) are seen as a transformative technology that can control the physical propagation environment in which they are embedded by passively reflecting radio waves in preferred directions and actively sensing this environment in receive and transmit modes. While such RISs have mainly been intended for communication purposes, they can provide great benefits in terms of performance, energy consumption, and cost for localization and mapping. These benefits as well as associated challenges are the main topics of this article.

Aircraft position estimation using angle of arrival of received radar signals

With increasing demand of air traffic, there is a need to optimize the use of available airspace. Effective utilization of airspace relies on quality of aircraft surveillance. Active research is carried out for enhancements in surveillance techniques and various methods are evaluated for future use. This paper evaluates the use of multiple signal classification (MUSIC) based angle of arrival (AOA) estimation along with multiangulation for locating aircrafts from their electromagnetic wave emission. The performance evaluation of the system is presented by evaluating the AOA estimation errors and position estimation (PE) errors. The errors are evaluated by comparing the estimated value to the actual value. An analysis on the system parameters, AOA error and PE error are presented in the end. AOA errors are affected by the AOA value (emitter bearing), number of array elements, SNR and resolution of AOA estimation algorithm. Errors in AOA estimation lead to PE errors. The simulation results show small errors for short ranges. The system performance can be improved at the expense of computational time by using higher MUSIC resolution and larger antenna arrays

Cascade AOA Estimation Algorithm Based on Flexible Massive Antenna Array.

The Angle-of-Arrival (AOA) has a variety of applications in civilian and military wireless communication fields. Due to the rapid development of the location-based service (LBS) industry, the importance of the AOA estimation technique has increased. Although a large antenna array is necessary to estimate accurate AOA information of many signals, the computational complexity of conventional AOA estimation algorithms, such as Multiple Signal Classification (MUSIC), is dramatically increased. In this paper, we propose a cascade AOA estimation algorithm employing CAPON and Beamspace MUSIC, based on a flexible (on/off) antenna array. First, this approach roughly finds AOA groups, including several signal AOAs using CAPON, by applying some of the antenna elements. Then, it estimates each signal AOA in the estimated AOA groups using Beamspace MUSIC by applying the full size of the antenna array. In addition to extremely low computational complexity, the proposed algorithm also has similar estimation performance to that of MUSIC. In particular, the proposed cascade AOA estimation algorithm is highly efficient when employing a massive antenna array. Representative computer simulation examples are provided to illustrate the AOA estimation performance of the proposed technique.

Site-Specific Online Compressive Beam Codebook Learning in mmWave Vehicular Communication

Millimeter wave (mmWave) communication is one viable solution to support Gbps sensor data sharing in vehicular networks. The use of large antenna arrays at mmWave and high mobility in vehicular communication make it challenging to design fast beam alignment solutions. In this paper, we propose a novel framework that learns the channel angle-of-departure (AoD) statistics at a base station (BS) and uses this information to efficiently acquire channel measurements. Our framework integrates online learning for compressive sensing (CS) codebook learning and the optimized codebook is used for CS-based beam alignment. We formulate a CS matrix optimization problem based on the AoD statistics available at the BS. Furthermore, based on the CS channel measurements, we develop techniques to update and learn such channel AoD statistics at the BS. We use the upper confidence bound (UCB) algorithm to learn the AoD statistics and the CS matrix. Numerical results show that the CS matrix in the proposed framework provides faster beam alignment than standard CS matrix designs. Simulation results indicate that the proposed beam training technique can reduce overhead by 80% compared to exhaustive beam search, and 70% compared to standard CS solutions that do not exploit any AoD statistics.

Active Vibration Control of a Large Space Antenna Structure Using Cable Actuator

A large space antenna structure will inevitably vibrate due to the space thermal environment and maneuver actions of the satellite. Such vibration will last continuously and affect normal function of the antenna. Therefore, a proper vibration control method is vital to keep the shape accuracy of the structure within an acceptable range. The research object of this paper is a large deployable planar phased array antenna that uses cables as active actuators. Research contents include the optimization of actuator position and the design of control law: both of which have considered the unilateral and saturated constraints of the cable actuator. First, the finite element method is used to obtain the modal information of the structure. Then the actuator position optimization method is established by using the controllability principle and the particle swarm optimization algorithm. Second, a piecewise cost function is adopted to design the control law by combining a linear quadratic regulator with a bang–bang regulator. In the numerical simulation, the vibration control process of an antenna structure consisting of 18 lattices is simulated and analyzed. The results prove that the proposed actuator position optimization method and the control law could effectively suppress the vibration and maintain the shape accuracy of the antenna structure.

Deep Learning for DOA Estimation in MIMO Radar Systems via Emulation of Large Antenna Arrays

We present a MUSIC-based Direction of Arrival (DOA) estimation strategy using small antenna arrays, via employing deep learning for reconstructing the signals of a virtual large antenna array. Not only does the proposed strategy deliver significantly better performance than simply plugging the incoming signals into MUSIC, but surprisingly, the performance is also better than directly using an actual large antenna array with MUSIC for high angle ranges and low test SNR values. We further analyze the best choice for the training SNR as a function of the test SNR, and observe dramatic changes in the behavior of this function for different angle ranges.

Cooperative Localization With Constraint Satisfaction Problem in 5G Vehicular Networks

5G new radio will provide a new paradigm in high accurate vehicle localization, reinforced by the use of large antenna arrays along with carefully designed broadband radio technology. However, a high computational load still remains unravelled in the context of cooperative localization, albeit with its advantages of high-precision localization. To alleviate such the computational burden, we develop a reliable technique of cooperative localization, addressed as a constraint satisfaction problem. A constraint satisfaction formalism for cooperative localization readily enables to recast a formulation of the decentralized optimization. Its efficient solution of the optimization is developed in a distributed manner. Simulation results demonstrate that the proposed approach saves the requested computational loads significantly while sustaining the satisfactory accuracy of cooperative localization.

Power Scaling of Full-Duplex Two-Way Millimeter-Wave Relay With Massive MIMO

In this paper, the asymptotic performance of a full-duplex (FD) millimeter wave (mmWave) two-way relay (TWR) system with a massive multiple-input multiple-output (MIMO) structure is analyzed. After applying conjugate array response vector-based precoding to a hybrid analog and digital MIMO structure in the mmWave band, the asymptotic spectral efficiency of the system as the number of antennas approaches infinity is derived. Based on the asymptotic performance and different system configurations, power scaling schemes are investigated. Considering different power scaling strategies at each node, eight power scaling cases are discussed, and the corresponding asymptotic spectral efficiencies are derived. The results show that interference and noise can be fully eliminated by increasing the number of antennas. A high spectral efficiency can be achieved in a system wherein all the nodes are equipped with large antenna arrays. If the numbers of antennas of node A and node B are both limited, then the system can achieve considerable spectral efficiency and energy efficiency. For both configurations, the power of node A and node B can be scaled down without spectral efficiency loss. However, if only one node is equipped with limited antennas, only the node with a massive array can achieve a higher spectral efficiency. Moreover, we analyze the effect of the FD self-interference (SI) levels. We show that the spectral efficiency decreases rapidly as the SI intensity increases, which is related to the capability of SI cancellation. Under ideal conditions, the FD system can achieve twice the spectral efficiency of its conventional half-duplex (HD) counterpart. However, the FD SI and the finite number of antennas degrade the spectral efficiency of the FD system.