Subarray Configuration Research Articles

Improving PA-MIMO radar detection performance through transceiver subarray configuration optimization under QoSbased model

Improving PA-MIMO radar detection performance through transceiver subarray configuration optimization under QoSbased model

Irregular Modular Subarrayed Phased Array Tiling by Algorithm X and Differential Evolution Algorithm

In this letter, an efficient and versatile method based on algorithm X and differential evolution algorithm is proposed to synthesize irregular modular subarrayed planar phased arrays with exact tiling. To alleviate the time-consuming problem of using algorithm X to synthesize large arrays, the proposed method obtains the subarray configuration with exact tiling through twice-partitioning operations. In the first partition process, the planar phased array is divided into several first-level subarrays. In the second partition process, the first-level subarrays are respectively divided into pre-specified irregular modular subarrays, called second-level subarrays. All feasible schemes for dividing the first-level subarrays and second-level subarrays can be obtained by algorithm X. Through the above partition process, the partitioning paradigm can be represented by only a few variables, which can be optimized by swarm intelligence algorithms. In this letter, the variables representing the subarray configuration are optimized by differential evolution algorithm to obtain excellent radiation performances. Three representative numerical examples are presented and discussed to assess the validity, efficiency, and reliability of the proposed method.

Helical Circular Array Configurations for Generation of Orbital Angular Momentum Beams

The vortex electromagnetic waves carrying the orbital angular momentum (OAM) are an increasing subject of study, and the design of a system capable of generating such waves is also of crucial importance. In this letter, a helical circular array (HCA) has been proposed to generate OAM radio beams. The proposed HCA has a more straightforward and more feasible scheme when compared to uniform circular arrays (UCAs) that require additional phase-shifting devices to form inter-element phases. The heights of the proposed HCA elements along the z-axis are exploited to generate the different OAM modes. For the high-order OAM modes, the height of the HCA is made more compact with the help of the proposed helical circular subarray (HCSA) configurations with spiral phase positions providing a linear phase delay with the azimuth angle. In addition, at high mode values, the HCSA structure creates a smoother OAM vortex beam than HCA. The full-wave simulation results show that the proposed HCA scheme can be used to generate vortex electromagnetic waves with a spiral phase wavefront structure.

Accelerating 3-D MUSIC Algorithm With Fast Fourier Transform for Collocated FDMA-MIMO Radar With Subarray Configuration

Frequency division multiple access (FDMA) waveform possesses good orthogonality and thus is used in Multiple-input multiple-output (MIMO) radar. Nevertheless, the transmitting steering vector of the FDMA-MIMO radar is dependent on both range and angle, and it has no form of a Vandermonde matrix at the subarray-level. As a result, target locating using the conventional three-dimensional (3D) MUSIC algorithm should be realized by 3D fine grid search, which yields a considerable computational burden. This paper proposes a fast implementation of the 3D MUSIC estimator via the 3D Fast Fourier Transform (FFT). By exploiting the reduced-dimensional matrix and the property of the Kronecker-product, the 3D-MUSIC spectrum can be reformulated in the form of Vandermonde matrix. Thus, 3D fine grid searching is avoided by using 3D FFT, which can work in the collocated FDMAMIMO radar with subarray configuration and significantly accelerate parameter estimation. Comparison experiments are performed to prove the rapidity and accuracy of the proposed algorithm.

Sub-6 GHz band massive MIMO antenna system for variable deployment scenarios in 5G base stations

A compact massive multi input multi output (MIMO) antenna system with 1 × 4 (sector) subarray configuration operating at sub-6 GHz range for 5th generation (5G) base stations has been designed and analysed in various geometries (rectangular, triangular, and hexagonal). The capacity of the system can be increased by more than 10 times whereas the energy efficiency can be increased 100 times using the massive MIMO system (Larsson et al. in IEEE Commun Mag 52(2):186–195, 2014). A maximum of 5 sectors has been used, with each sector comprising of 1 × 4 subarray elements. Each sector consists of three layers, in which 1 × 4 patches are located on its top layer whereas it’s feeding network and ground plane are placed at the bottom layer and middle layer respectively. The entire system can operate in two modes, individual port operation and massive MIMO array operation with beam steering capabilities. The measured bandwidth of the system is 140 MHz that covers the frequencies from 3.36 to 3.50 GHz in sub-6 GHz band. The overall dimension of a unit subarray in terms of length, width and height is 280.5 × 56.1 × 2 mm3. The gain of an individual port is found to be 12.77 dBi and the overall gain of a single panel with 5 sectors arranged in rectangular form is 19.73 dBi. Mutual coupling among all the ports has been kept less than − 16 dB. The operating frequency range of the antenna array system is chosen in the range of 3.3–3.8 GHz, as this band has been allocated and targeted across the globe to enable 5G in Sub-6 GHz band.

Synthesis of Modular Subarrayed Phased-Array With Shaped-Beams by Means of Sequential Convex Optimization

In this letter, an efficient method based on sequential convex optimization is proposed to synthesize modular subarrayed phased-arrays with shaped beams. The proposed method consists of two steps. In the first step, the subarray configuration with exact tiling is acquired through solving iterative convex optimization problems. To obtain the arrangement of subarrays with exact tiling, the binary vector sparsity problem is relaxed to be a reweighted <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\boldsymbol{l}}_1}$</tex-math></inline-formula> -norm minimization problem which can be solved efficiently by interior point method. In general, there are plenty of exact tiling configurations. To obtain the subarray configuration which is more conductive to radiating the target shaped-beam, the limiting conditions of the shaped-beam are added to the solution process of exact tiling. In the abovementioned solution process, the excitations of the subarrays can be obtained at the same time. However, due to the exact tiling constraints in the solution process, the obtained excitations are usually not the optimal solution for the obtained exact tiling configuration. Therefore, in the second step of the proposed method, the convex optimization method is used again to recompute the excitations of the modular subarrayed phased-array. Two numerical examples are implemented to verify the validity and reliability of the proposed method.

Shaped-Beam Pattern Synthesis With Sidelobe Level Minimization via Nonuniformly-Spaced Sub-Array

This article deals with the low-sidelobe shaped-beam pattern synthesis (SBPS) problem using two nonuniformly spaced subarray configurations, including amplitude and amplitude–phase subarray configurations. An optimization model is proposed for the SBPS problem to minimize the peak sidelobe level by jointly optimizing the subarray configuration and element excitations/positions. A typical advantage of the proposed model is to reduce the system control points while maintaining the benign array performance. However, the formulated problem is a mixed-integer nonconvex one, which makes it challenging. Besides, this problem cannot be directly solved due to the existence of coupling optimization variables. Thus, a set of auxiliary variables is introduced to move the coupling optimization variables into equality constraints. These equality constraints are converted into quadratic penalty forms and are added to the objective function. Then, an efficient iterative algorithm is proposed using the penalty-based optimization method, which solves the original problem by iteratively solving a series of subproblems based on the inexact block coordinate descent technique. Numerical examples with different beam patterns are performed to verify the effectiveness of the proposed algorithm.

An Effective Hybrid Synthesis Strategy of Multibeam Subarray

In this paper, an effective hybrid method is proposed to design the subarrays generating multiple functional beams. In the process of synthesis, one of the target patterns is selected as the primary pattern which is generated at the element level. Other secondary patterns are generated at the subarray level by dividing the elements into non-overlapped subarrays and utilizing attenuators and phase shifters at the subarray outputs. To simplify the complexity of the feed network, the subarray configurations of secondary patterns are the same. The proposed method consists of two steps. In the first step, the subarray configuration of the phased array is optimized by the K-means clustering method. In the second step, the convex optimization method is applied to acquiring the complex weighting coefficients of subarrays, which can improve the accuracy of the synthesized secondary patterns. A series of numerical examples demonstrate the effectiveness of the proposed method.

On the Effectiveness of Rotation-Based Arrangement Optimization in the Pattern Synthesis of Subarrayed Phased Array

This letter presents a rotation-based optimization method for pattern synthesis of subarrayed phased arrays. In order to keep a good beam scanning ability at different steering angles, the optimization problem is reasonably defined where the objective is taken as minimizing the maximum sidelobe level at a series of steering angles, and both the arrangement variables and the scanning variables are optimized simultaneously. The mutual coupling of the iteratively rotated arrays is rigorously considered in the synthesis. In order to solve the synthesis problem effectively, the design sensitivities are derived analytically and the synthesis is actualized by using a gradient-based algorithm. Typical examples, with considering different regular subarray configurations and the state-of-art irregular subarray configurations, are provided to validate the effectiveness of the proposed approach.

The Thousand-Pulsar-Array programme on MeerKAT – II. Observing strategy for pulsar monitoring with subarrays

ABSTRACT The Thousand-Pulsar-Array (TPA) programme currently monitors about 500 pulsars with the sensitive MeerKAT radio telescope by using subarrays to observe multiple sources simultaneously. Here we define the adopted observing strategy, which guarantees that each target is observed long enough to obtain a high-fidelity pulse profile, thereby reaching a sufficient precision of a simple pulse shape parameter. This precision is estimated from the contribution of the system noise of the telescope, and the pulse-to-pulse variability of each pulsar, which we quantify under some simplifying assumptions. We test the assumptions and choice of model parameters using data from the MeerKAT 64-dish array and the Lovell and Parkes telescopes. We demonstrate that the observing times derived from our method produce high-fidelity pulse profiles that meet the needs of the TPA in studying pulse shape variability and pulsar timing. Our method can also be used to compare strategies for observing large numbers of pulsars with telescopes capable of forming multiple subarray configurations. We find that using two 32-dish MeerKAT subarrays is the most efficient strategy for the TPA project. We also find that the ability to observe in different array configurations will become increasingly important for large observing programmes using the Square Kilometre Array telescope.

Coherence optimised subarray partition for hybrid MIMO phased array radar

Hybrid MIMO phased array radar (HMPAR) is widely recognized in the research of radar systems owing to its capacity to provide a balance or trade-off between transmit coherent gain and waveform diversity gain. The balance or trade-off between these two gains is closely related to spatial coherence between different arrays, represented by the degree of cross-correlation between steering vectors over different angles. Proper subarray partitions can provide an extra degree of freedom for optimising the coherence of the array manifold. A coherence optimised subarray partition for HMPAR is proposed with an analysis of connections between coherence and subarray partitions. First, the definition of coherence of array manifold is presented, and its connection between beampattern and the signal to interference plus noise ratio (SINR) is analysed. Next, the problem of optimising array manifold coherence is transformed into the discrete coherence optimization of the steering vector codebook. By properly selecting different codewords with the proper degree of correlation between each other, coherence between the target and interference steering vectors is optimised. The original combinatorial problem is approximated by a series of subproblems, which is solved in iteratively. Numerical results revealed that the proposed subarray partition provides lower coherence, lower beampattern peak sidelobes and higher SINR compared with` other subarray configurations.

A 368 × 184 Optical Under-Display Fingerprint Sensor Comprising Hybrid Arrays of Global and Rolling Shutter Pixels With Shared Pixel-Level ADCs

This study proposes a $368\times184$ optical under-display fingerprint sensor designed and prototyped using the 0.11- $\mu \text{m}$ CIS technology. The prototype sensor includes a hybrid array of global and rolling shutter pixels and a shared pixel-level analog-to-digital converter (ADC) embedded in a 32-pixel subarray configuration. It features a fast response time and low power consumption. By directly coupling the ramp signal to a floating diffusion capacitor with shared pixels, the best compromise between full-well capacity (FWC) and conversion gain is achieved. Two sets of memory (184 $\times $ 92 bytes) are also embedded in the pixel array to save the costs of external memory. A dynamic range of 110 dB is achieved with eight-segment automatic exposure and a contrast enhancement scheme for black level correction. A pixel binning process is used to improve the sensor sensitivity. The measured FWC, sensitivity, and conversion gain are 95 ke-, 800 ke-/lux-s, and $340~\mu \text{V}$ /e-, respectively. The prototype fingerprint sensor consumes only 15 mW with a 3.3-V supply voltage. The sensor chip size is 9.74 mm $\times \,\, 4.6$ mm, and the sensing area is 8 mm $\times \,\, 4$ mm, which is 71.4% of the chip size. The resolutions of the sensor without and with the pixel binning process are 1154 and 572 dpi, respectively.

A Toolbox of Subarrays for Optimizing Wide-Angular Scanning Arrays Using Trade-Offs Between Scan Loss and Side Lobe Level

A novel approach is proposed for building a planar array derived from linear arrays using a toolbox of different types of subarrays located parallel and perpendicular to the linear array axes. The array design assumes constant element patterns and focuses on rectangular array applications with one dimensional, wide-angular beam scanning. Optimization criteria concern a trade-off between side lobe level performance, directive gain scan-loss, reducing the number of element controls and maximizing the use of phase-only elements for beam steering. All subarray configurations and functionalities, for improving the full array performance in sidelobe level and scan-loss compensation, are analyzed and validated in detail. The step-by-step integration of different subarrays starts from the center part of the array. This center part is a linear subarray along the major axis of the rectangular array with uniform maximum amplitude and spatially stretched. This subarray is combined with cross-line subarrays perpendicular to this center axis. At both edges of the center array, two in-line, uniform-amplitude and stretched subarrays are added and combined with cross-line subarrays. The amplitude distribution of the 3 in-line subarrays and the cross-line subarrays allows for lowering the sidelobe level in the plane of scanning. Finally, at both ends of the three in-line subarrays, subarrays with two and five elements are applied for reducing the scan-loss. By assuming <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$cos(\vartheta)$ </tex-math></inline-formula> element pattern results are given for a planar rectangular array with 41 elements length and 3 elements width. To lower cost and higher power efficiency, the array uses only 33 multi-bit phase shifters, 12 1-bit phase switches, and 4 attenuators for amplitude control. Optimized broadside and 60° scanning patterns are compared and show improved performance in directive gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D=24.4$ </tex-math></inline-formula> dBi (broadside), <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D=19.9$ </tex-math></inline-formula> dBi (60°) and in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {SLL}=-21.6$ </tex-math></inline-formula> dB (broadside), <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {SLL}=-19.5$ </tex-math></inline-formula> dB (60°).

Direction-of-Arrival Estimation of Far-Field Sources Under Near-Field Interferences in Passive Sonar Array

For passive sonar arrays, when far-field sources lie in a masking region caused by near-field interferences, direction-of-arrival (DOA) estimations of the interfered far-field sources become difficult. To mitigate the interference, we propose a near-field interference mitigation (NFIM) beamformer that utilizes subarrays and a proposed azimuth-domain filter without any source constraint. For the proposed method, this paper mathematically analyzes the masking region and the subarray configuration to separate the beams of the far-field source from the near-field interference and designs the proposed azimuth-domain filter in the proposed zeta domain. The suppression filter is implemented for all subarrays to mitigate the interferences, and the filtered outputs of all subarrays are combined to suppress residual interferences. Computer simulations show that the proposed NFIM beamformer mitigates the interferences and increases the DOA estimation performance compared with those of conventional methods.

Eight-Port Feed Radial Line Slot Antenna for Wireless Power Transmission

This article proposes a circular sector subarray to equalize input power to rectifiers and an eight-port radial line slot antenna (RLSA) with the circular sector subarray. Rectifiers are nonlinear components and have the optimum input power. To maximize RF-DC conversion efficiency, the input power to the rectifiers should be the uniform and optimum input power. The circular sector subarray configuration enables uniform power feeding to multiple ports by dividing the circular aperture into circular sector shapes. The eight-port RLSA has eight microstrip lines to divide the circular aperture to eight circular sector subarrays. The design methodology of the eight-port RLSA is detailed and it is fabricated by printed circuit board technology. The fabricated antenna showed good agreement with the simulated characteristics. Transmission between the eight-port RLSA and a one-port RLSA was measured, and 60% transmission with 280-mm separation was confirmed. Transmission to each port has a 1.4 to 3.4-dB deviation because of the circumference deviation of the one-port antenna aperture distribution. This deviation can be improved by enhancing the uniformity of the one-port antenna aperture distribution.

A Sequential ESPRIT Algorithm Based on a Novel UCSA Configuration for Parametric Estimation of Two-Dimensional Incoherently Distributed Source

Two-dimensional distributed source is a more realistic model to represent the target signal propagation in such fields as radar, sonar, and wireless communication. This paper presents a novel uniform circular sub-array (UCSA) configuration, which can be used to accurately estimate parameters of multiple two-dimensional incoherently distributed (TDID) sources. By sequentially utilizing the mapping relationship between the generalized array manifold, which has the spatial translation invariant relationship, and the signal subspace of TDID source, a closed-form solution of four parameters (central and spread parameters within azimuth and elevation dimension) of every TDID source can be obtained with low computational complexity. Furthermore, by properly using the signal subspace, the estimation accuracy is improved significantly. Numerical simulations illustrate the properties of the proposed method and show that it can simultaneously improve the robustness with respect to the scattering size and uncertainty of the spatial distribution. The proposed method has the potential to be used for fast and accurate multi-TDID source localization with arrays of small aperture and few array elements.

Design of Concentric Ring Antenna Arrays Based on Subarrays to Simplify the Feeding System

The global synthesis for antenna arrays that produce a desired radiation pattern is a scientific symmetry problem. This paper deals with the design of concentric ring antenna arrays to simplify the feeding system using a cophasal subarray configuration. This simplification in the feeding network is achieved by the reduction of phase shifters via a proper clustering of radiators applying one amplitude and one phase excitation by subarray in the array system. The array design for this geometry considers an optimization process based in differential evolution to reduce the side-lobe level, resulting in simplification of the feeding network. Simulation results based on CST Microwave Studio and HFSS are provided to verify the accuracy of the array model and to take mutual coupling into account. These simulations are provided using a circular patch as antenna element to generate a scannable array pattern over the elevation plane. Furthermore, an analysis of the manufacturing tolerances was made to verify the reliability of our design.

Optimal Excitation Matching Strategy for Sub-Arrayed Phased Linear Arrays Generating Arbitrary-Shaped Beams

The design of phased arrays able to generate arbitrary-shaped beams through a sub-arrayed architecture is addressed here. The synthesis problem is cast in the excitation matching framework, so as to yield clustered phased arrays providing optimal trade-offs between the complexity of the array architecture (i.e., the minimum number of control points at the sub-array level) and the matching of a reference pattern. A synthesis tool based on the k-means algorithm is proposed for jointly optimizing the sub-array configuration and the complex sub-array coefficients. Selected numerical results, including pencil beams with sidelobe notches and asymmetric lobes as well as shaped main lobes, are reported and discussed to highlight the peculiarities of the proposed approach also in comparison with some extensions to complex excitations of state-of-the-art sub-array design methods.

Main lobe jamming suppression via blind source separation sparse signal recovery with subarray configuration

The performance of the modern radar systems will degrade significantly in the presence of main lobe jamming. In this study, a new methodology is introduced to suppress multiple main lobe jammings while accomplishing the directions of arrival (DOAs) estimation of the multiple targets. Specifically, the signal model of a specific subarray configuration accounting for jamming and target signals is developed. Then, blind source separation method is utilised to separate the target and jamming signals in each subarray. Furthermore, the separated target signals of all subarrays are jointly imposed to estimate DOAs of targets through resorting to sparse signal recovery approach. Finally, numerical simulations are provided to assess the performance of the proposed algorithm exhibiting the favourable capabilities in terms of the strong main lobe jamming suppression and the DOAs estimation of multiple targets.

Challenges and Limitations of the Cross-Polarization Suppression in Dual-Polarization Antenna Arrays Using Identical Subarrays

In this article, challenges and limitations of using cross-polarization suppression methods for dual-linear polarization antenna arrays are presented. A simple probe-fed patch antenna and high-performance, dual-polarized hybrid-fed patch antennas are used for this article. The image feed method is used for improving the cross-polarization level and increasing the geometrical symmetry of a very large phased array antenna. It is shown that decomposing the antenna radiation pattern to its even and odd components for calculating $2\times $ 2-element subarray radiation pattern has fundamental limitations and none of four different $2\times $ 2-element and $4\times $ 4-element subarray configurations will entirely suppress the sidelobe issue of configured arrays. The accuracy of using embedded element pattern for calculating the radiation pattern of very large array antennas with identical subarrays is studied, and an accurate procedure for predicting array antenna radiation pattern is proposed. The appearance of undesired sidelobes has been examined, and optimal design for mitigating the sidelobe issue associated with the large array of identical subarrays with image configuration is presented.