Array Topology Research Articles

New architectures for micromechanical coupled beam array filters

Coupled resonator filters implemented as microelectromechanical systems (MEMS) offer performance advantages as band-pass filters at MHz frequencies. Here new designs based on resonant cavities for acoustic slow waves are developed to allow alternative frequency responses. Derivation of the lumped element model for coupled beam systems with in-plane motion from Rayleigh–Ritz perturbation theory is first reviewed. Departures from ideal behaviour caused by mechanical and electrostatic detuning are resolved. Slow wave theory is then used to develop linear array topologies with novel responses including band-stop and comb filtering with controlled filter roll-off. A systematic procedure is developed to allow rapid identification of design parameters without the need for lengthy numerical simulation, using the lumped element, stiffness matrix and finite element methods to investigate the layout parameters of initial design concepts, detailed mechanical effects and detailed electrostatic effects, respectively. High performance is demonstrated, with good agreement between the models.

Sparse Array Beamforming Design for Wideband Signal Models

We develop sparse array receive beamformer design methods achieving maximum signal-to-interference plus noise ratio (MaxSINR) for wideband sources and jammers. Both tapped delay line (TDL) filtering and the DFT realizations to wideband array processing are considered. The array sparsity stems from the limited number of available RF transmission chains that switch between the sensors, thereby configuring different arrays at different times. The sparse array configuration design problem is formulated as a quadratically constraint quadratic program (QCQP) and solved by using SDR (semidefinite relaxation). A computationally viable approach through SCA (successive convex relaxation) is also pursued. In order to realize an implementable design, in presence of missing autocorrelation lags, we propose parameter-free block Toeplitz matrix completion to estimate the received data correlation matrix across the entire array aperture. It is shown that the optimum wideband sparse array effectively utilizes the array aperture and provides considerable performance improvement over suboptimal array topologies.

Experimental Investigation of PV Array Interconnection Topologies at Nonuniform Aging Condition for Power Maximization

In vast Photovoltaic (PV) power plant the output power production decreases significantly due to the fact of non-uniform aging of PV modules. The non-uniform aging of PV modules increases current-voltage (I-V) mismatch among the array modules and causes mismatch power loss (MPL). There are different interconnection topologies of the PV module in an array to minimize MPL and thus maximize the array output power. This paper investigates four different interconnection topologies experimentally on a 4×4 nonuniformly aged PV array. Three different patterns of PV module rearrangement are used to investigate the performance of each interconnection topology in terms of array output power and MPL. The experimental results show that the proposed interconnection topology is yields about 3.28% (average) higher output power than that of the most commonly used series-parallel array topology.
 GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 6(1), Dec 2019 P 39-45

Response to “Comment on ‘Sliding planar conjoined cut-wire-pairs: A novel approach for splitting and controlling the absorption spectra’” [J. Appl. Phys. 128, 126101 (2020)

In the Comment by S. C. Bakshi and D. Mitra [J. Appl. Phys. 128, 126101 (2020)], it is claimed that “cross-polarization reflection was ignored in calculation of absorptivity of that structure,” “the actual absorptivity of the new peaks [is] extremely poor (around 40%),” and hence the vertical sliding mechanism of conjoined cut-wire-pairs (CCWPs) “can't be adopted for efficient switching/tuning of the absorption spectra.” In this Response, we will demonstrate that these claims are not only unfair but also incorrect as they result from an unfortunate fundamental mistake they made in the attempt of replicating the effective free-space absorber array topology implied in the original article [J. Appl. Phys. 124, 105103 (2018)]. The use of “CCWP unit-cell within a metallic waveguide” scenario in the original work implies the realization of an infinitely large periodic array of a “super-cell,” whose structure is determined by the well-known mirror image effect of the perfect electrical conductor type boundary condition imposed by the conducting walls of the waveguide. When this fact is ignored, but instead the free-space array is formed by simply repeating the same asymmetric CCWP unit-cell periodically, a completely different absorber array topology is obtained, which is clearly irrelevant to the original design. Therefore, the results reported in the Comment belong to an alternative absorber array; they do not represent the performance of the original design. In this Response, we will clarify our points outlined above to refute the claims made in the Comment to demonstrate the validity of the original results and the usefulness of the suggested absorber array for practical purposes.

On One-Bit Line-of-Sight MIMO Communications at Flexible Communications Distances

The classic line-of-sight (LoS) MIMO systems optimize antenna spacings according to the communication distance, and the subchannels of fixed symmetric arrays are sensitive with distance variations. Under array aperture constraints, this letter shows that asymmetric array topologies can provide robust spatial multiplexing over a broad distance range. To reduce the implementation costs and power consumption, we further propose to use one-bit quantization for both transmitting and receiving at the terminal of more antennas. Finally, with evaluations using Bussgang decomposition based mutual information lower bound, the proposed one-bit LoS MIMO system is verified with its significant and robust MIMO gain.

Double Patch Antenna Array for Communication and Out-of-band RF Energy Harvesting

Abstract This paper presents a patch antenna array topology for Simultaneous Wireless Information and Power Transfer (SWIPT) applications. The resulting Double Patch Antenna Array (DPA) is composed of two patch antennas operating at different frequencies and fabricated on a unique substrate. One of the patches operates at the 1.8 GHz mobile communication band and is used for wireless communication, while the other one operates at the 2.4 GHz Industrial, Scientific, and Medical (ISM) band, and is used for Radio Frequency Energy Harvesting (RFEH). The analyzes and measurements carried out have shown that the adopted topology has satisfactory performance for communication, with a gain of 1.5 dBi, and for out-of-band energy harvesting, with a Vout of 160 mV at 2.45 GHz. These results indicate this approach as a promising strategy for low-power wireless applications.

Continuously steerable differential beamformers with null constraints for circular microphone arrays.

Differential beamforming combined with microphone arrays can be used in a wide range of applications related to acoustic and speech signal acquisition and recovery. A practical and useful method for designing differential beamformers is the so-called null-constrained method, which was developed based on linear arrays and requires only the nulls' information from the target directivity pattern. While it is effective and easy to use, this method is found not suitable for designing steerable differential beamformers with circular arrays. This paper reexamines this technique in the context of circular differential microphone arrays. By analyzing the properties of the circular array topology, the null-constrained method is extended to include symmetric constraints, which is inherent in the design of circular arrays. This extension yields a design method for fully steerable differential beamformers that require only minimum information from the target beampattern. Simulations justify the theoretical analysis and demonstrate the good properties of the developed method.

Automatic AI-Driven Design of Mutual Coupling Reducing Topologies for Frequency Reconfigurable Antenna Arrays

An automatic artificial intelligence (AI)-driven design procedure for mutual coupling reduction and a novel isolator are proposed for a frequency reconfigurable antenna array. The design process is driven and expedited by the parallel surrogate model-assisted differential evolution for antenna synthesis (PSADEA) method. The reconfigurable array element can switch its operation between the 2.5 GHz ISM band and the 3.4 GHz WiMAX band. By introducing the proposed isolator, the mutual coupling in the higher and lower band is reduced by 8 and 7 dB, respectively. The reconfigurable array was prototyped, and measurements agree well with simulations, verifying the validity of the proposed concept. Although used for a specific antenna in this communication, the proposed AI-driven design strategy is generic and can easily be employed for other array topologies.

Null Beamsteering Using Distributed Arrays and Shared Aperture Distributions

In this work, a novel technique using closed-form expressions is rigorously surveyed to collaboratively nullsteer uniformly distributed, planar ring, and volumetric shell distributions. To assess the radiation behavior of these geometries circular tapers is of interest for their attractiveness in derivation, design, application, and mathematical simplicity. A rigorous mathematical derivation is used for the generation of closed-form expressions of the mean-valued radiation characteristics. The numerical simulations are performed using both ANSYS HFSS and MATLAB using a finite-element distribution. To validate the analytical models, we include the measured results of a uniformly distributed ring array topology, constrained to a set of 18 elements and a uniformly distributed shell array topology constrained to 16 elements. The results of all methods are compared to demonstrate exceptional agreement in the recommended theoretical analysis. This process follows differently from traditional phased array nulling methods, which apply the unique amplitude tapers along individual phased array elements. Unlike typical adaptive beamforming algorithms, this process does not require the estimation of second-order statistical metrics and avoids expansions of large polynomial equations. It uses shared aperture characteristics in order to generate null beams simultaneously. This can also be extended to widen null widths from the compounding of these shared aperture distributions, which is shown in simulation.

Parametric indicators for partial shading and fault prediction in photovoltaic arrays with various interconnection topologies

Photovoltaic arrays are mainly installed to generate maximum power and serve the load demand. However, the arrays are susceptible to various unpredictable scenarios such as partial shading and electrical faults that reduce the overall performance and result in serious power loss, hotspot formation, and severe damage to the modules. So, partial shading and fault detection algorithms are considered to be an important constituent to avoid unwanted power loss and system failures. Most of the algorithms use the voltage and current variation approach as detecting indicators for shading and faults. However, the array voltage and current can also vary due to certain other factors such as module temperature difference that result in reliability reduction due to false detection. In this paper, the sensitivity of various widely used array topologies to partial shading and electrical faults have been studied using various electrical parametric indicators. The variability of these indicators to shading and faults has been studied for determining the most relevant indicators that can be used for shade and faults detection in all array topologies. Also, the topologies have been studied using the characteristics curves, power generation, and mismatch losses to determine the most fault-tolerant topologies. The entire study has been performed in the MATLAB/Simulink environment and validated using experimental analysis. It has been found that the indicators largely varies to the shading/faults in the arrays and differs for different topologies and can be used to detect/predict faults. Also, it has been found that during minimum (10%) and maximum (90%) system shading, the parallel topology generated higher power nearly equal to 88.95% and 19.48% of the unshaded scenario respectively. However, during 90% system fault, all the topologies generated nearly equal power i.e. 11.27% of the no-fault scenario.

Evaluation of Mathematical Model to Characterize the Performance of Conventional and Hybrid PV Array Topologies under Static and Dynamic Shading Patterns

The analysis and the assessment of interconnected photovoltaic (PV) modules under different shading conditions and various shading patterns are presented in this paper. The partial shading conditions (PSCs) due to the various factors reduce the power output of PV arrays, and its characteristics have multiple peaks due to the mismatching losses between PV panels. The principal objective of this paper is to model, analyze, simulate and evaluate the performance of PV array topologies such as series-parallel (SP), honey-comb (HC), total-cross-tied (TCT), ladder (LD) and bridge-linked (BL) under different shading patterns to produce the maximum power by reducing the mismatching losses (MLs). Along with the conventional PV array topologies, this paper also discusses the hybrid PV array topologies such as bridge-linked honey-comb (BLHC), bridge-linked total-cross-tied (BLTCT) and series-parallel total-cross-tied (SPTCT). The performance analysis of the traditional PV array topologies along with the hybrid topologies is carried out during static and dynamic shading patterns by comparing the various parameters such as the global peak (GP), local peaks (LPs), corresponding voltage and current at GP and LPs, fill factor (FF) and ML. In addition, the voltage and current equations of the HC configuration under two shading conditions are derived, which represents one of the novelties of this paper. The various parameters of the SPR-200-BLK-U PV module are used for PV modeling and simulation in MATLAB/Simulink software. Thus, the obtained results provide useful information to the researchers for healthy operation and power maximization of PV systems.

Cylindrical MIMO Array-Based Near-Field Microwave Imaging

Microwave/millimeter-wave imaging has a wide prospect in applications of concealed weapons detection. The main problem of the existing techniques lies in the contradiction between the imaging speed and the system cost. In this respect, a cylindrical sparse multiple-input–multiple-output (MIMO) array topology is proposed, which has no mechanical scanning so as to achieve fast sampling process. Furthermore, it can provide more angular observations than the mainly used systems with a planar aperture. To speed up the image reconstruction process, a phase center approximation-based transformation is made to convert the multistatic sampling scheme to its monostatic counterpart for which there are more fast and tractable imaging algorithms. Then, a phase calibration method is presented after we analyze the error of such an equivalence. In so doing, the cylindrical MIMO topology is transformed into an approximate monostatic one. Finally, a wavenumber domain algorithm is employed to attain the fast image reconstruction. Numerical simulations are provided to demonstrate the performance improvement of the proposed technique.

High Temperature Superconducting Halbach Array Topology for Air-cored Electrical Machines

Air-cored electrical machines have attracted increasing attention in applications related to aircraft and wind power because they can eliminate core losses and decrease the total mass. However, the limited magnetic flux in air-cored machines has restricted their power level. In order to improve the power density and efficiency while further reducing the weight of air-cored electrical machines, a novel field winding topology composed of high temperature superconducting (HTS) Halbach Array magnets (HAM) has been proposed in this paper. C-GEN is an innovative multi-stage air-cored generator technology with permanent magnets, which has been demonstrated at laboratory scale. Taking a 1 MW C-GEN generator prototype as the example machine, an H -formulation founded HTSHAM model has been built in COMSOL Multiphysics with the homogenization method. Simulation results show that the proposed HTSHAM C-GEN generator can achieve a power density more than 4 times higher than the conventional design with permanent magnets (PM), with a reduced magnet weight of around half of the previous prototype. The proposed HTSHAM represents a generic approach for the design of fully air-cored superconducting synchronous machines, eliminating heavy ferromagnetic material, and thus provides a useful reference for the design of low-weight air-cored electrical machines with a high power density.

Mathematical Analysis of Solar Photovoltaic Array Configurations with Partial Shaded Modules

Solar-based photovoltaic (SPV) cells produce power from sunlight through the photovoltaic effect. The yield voltage of a single PV cell is small, so the voltage is extended by interfacing PV cells in series arrangement known as PV module or panel. Solar PV array comprises of series and parallel connections of modules in the grid structure with a few columns and rows. The various kinds of SPV array configurations or topologies are shaped by changing the number of electrical connections between module to module in an array. This paper presents the mathematical examination of 6×6 size regular SPV array configurations, including Total-Cross-Tied, Parallel, Honey-Comb, Series-Parallel, Series, Bridge-Linked types beneath un-shading case, and different proposed shading cases (primarily short narrow, short wide, long narrow, and long wide shadings). The electrical proportionate circuit of the SPV array setups was analyzed by Kirchhoff’s laws at distinctive nodes and loops in a sun powered PV array. The location of global maximum power point (GMPP) was determined hypothetically and distinguished in Matlab/simulation software at various shading conditions. Citation:  Raju, V.B., and Chengaiah, C. (2020). Mathematical Analysis of Solar Photovoltaic Array Configurations with Partial Shaded Modules. Trends in Renewable Energy, 6, 121-143. DOI: 10.17737/tre.2020.6.2.00115

Performance assessment of high-density diffuse optical topography regarding source-detector array topology.

Recent advances in optical neuroimaging systems as a functional interface enhance our understanding of neuronal activity in the brain. High density diffuse optical topography (HD-DOT) uses multi-distance overlapped channels to improve the spatial resolution of images comparable to functional magnetic resonance imaging (fMRI). The topology of the source and detector (SD) array directly impacts the quality of the hemodynamic reconstruction in HD-DOT imaging modality. In this work, the effect of different SD configurations on the quality of cerebral hemodynamic recovery is investigated by presenting a simulation setup based on the analytical approach. Given that the SD arrangement determines the elements of the Jacobian matrix, we conclude that the more individual components in this matrix, the better the retrieval quality. The results demonstrate that the multi-distance multi-directional (MDMD) arrangement produces more unique elements in the Jacobian array. Consequently, the inverse problem can accurately retrieve the brain activity of diffuse optical topography data.

A Generic Spiral MIMO Array Design Method for Short-Range UWB Imaging

In this letter, we propose a generic design method of spiral multiple-input–multiple-output (MIMO) antenna arrays for short-range ultrawideband imaging applications. This approach offers superior uniformity and low element shadowing properties in an effective aperture. Moreover, several variables are provided to further tune the positioning of elements. The proposed method avoids a disruptive array topology that exists in the curvilinear array for certain transmit and receive array combinations. Two spiral MIMO arrays are developed and shown to have better focusing property than curvilinear and rectangular arrays. Experimental results are also demonstrated to verify the imaging capability of the proposed spiral array.

Mitigation of Mismatch Power Losses of PV Array under Partial Shading Condition using novel Odd Even Configuration

In this paper, the effect of Partial Shading Condition (PSC) on various solar photovoltaic (PV) array topologies has been studied extensively. PSC reduces the maximum power of a PV array and produces multiple Maximum Power Points (MPPs) in the PV characteristics. A novel PV array configuration, named as the Odd Even Configuration (OEC) has been proposed to mitigate the effects of PSC under a diagonally progressing shadowing scenario and performance parameters like mismatch power loss, Fill Factor (FF) and Performance Ratio (PR), have been measured. The performance of the proposed OEC has been compared with pre-existing standard configurations such as TCT, SP-TCT, BL-TCT and BL-HC. Another recently proposed configuration has also been used for comparison. The effect of variation in temperature on the shade dispersion effect has also been studied. All the considered PV array configurations have been modeled in MATLAB/Simulink environment. The proposed OEC configuration is found to be superior to other configurations for all the PSCs considered, with minimum power loss and improved FF.

Joint 2D DOA and Doppler frequency estimation for L-shaped array using compressive sensing

A joint two-dimensional (2D) direction-of-arrival (DOA) and radial Doppler frequency estimation method for the L-shaped array is proposed in this paper based on the compressive sensing (CS) framework. Revised from the conventional CS-based methods where the joint spatial-temporal parameters are characterized in one large scale matrix, three smaller scale matrices with independent azimuth, elevation and Doppler frequency are introduced adopting a separable observation model. Afterwards, the estimation is achieved by L 1 -norm minimization and the Bayesian CS algorithm. In addition, under the L-shaped array topology, the azimuth and elevation are separated yet coupled to the same radial Doppler frequency. Hence, the pair matching problem is solved with the aid of the radial Doppler frequency. Finally, numerical simulations corroborate the feasibility and validity of the proposed algorithm.

Current collector optimizer topology to extract maximum power from non-uniform aged PV array

Centralized inverter technology is one of the most common architectures of the PV installation, which interfaces a large number of PV panels that configured in series-parallel (SP) combination to the grid. However, the power generated from centralized inverter architecture based on SP array topology is significantly reduced under the non-uniform aging condition. Non-uniform aging of PV panels is a common problem in the PV generation plants, as they often operate under harsh outdoor environmental conditions for a long service period. Due to the elevated price of replacing aged PV panels with new ones, it is preferable to improve the power extracted from aged PV systems. This paper proposes a circuit-based topology known as current collector optimizer (CCO) topology to enhance the performance of centralized inverter technology under the uneven aging condition of PV modules. According to the results, the maximum power extracted from the non-uniform aging PV array is substantially increased by using the CCO topology compared to the conventional SP array topology with bypass diodes. With CCOs, the PV array characteristics have a unique maximum power point (MPP) which can be easily followed by a simple MPP tracking algorithm, subsequently, the CCO topology does not suffer from misleading power losses. The proposed topology requires offline rearrangement of aged modules to obtain the optimum power if only the degradation rate of short-circuit current is used to assess the aging process. Furthermore, the CCO topology operates close to optimum power if the degradation rate of open-circuit voltage is taken into account.

Near-Field 3D SAR Imaging Using a Scanning Linear MIMO Array With Arbitrary Topologies

For near-field synthetic aperture radar (SAR) imaging, frequency domain imaging algorithms typically require the array elements to be uniformly arranged to facilitate the application of fast Fourier transform (FFT) operations; this greatly restricts the array types that can be used for practical applications. For arrays with non-uniformly positioned antennas, no general and efficient imaging algorithm is available yet. To address this issue, an effective algorithm for efficient three-dimensional (3D) SAR imaging with arbitrary linear multi-input-multi-output (MIMO) array topologies is proposed. Specifically, non-uniform FFT (NUFFT) technology is utilized to tackle the non-uniform sampling issues in both the spatial and the wavenumber domain. Despite the intuitive idea, to achieve satisfied imaging, some issues are non-trivial and should be carefully addressed. Both simulations and experiments show the superiority of the proposed algorithm on computational complexity while maintain the same high imaging precision compared with the back-projection algorithm (BPA). Moreover, we suggest that the concept of NUFFT-based imaging can also be generalized to other imaging regimes with arbitrary array configurations.