A Parallelized Fast Array Analysis Approach

The Origin of Spurious Solutions in Computational Electromagnetics

This study investigates and evaluates applications of the adjoint problem and its solution in frequency-domain computational electromagnetics (CEM). The study establishes and validates adjoint-based applications including higher order parameter sampling, a posteriori error estimate evaluation, and p- and h-refinements. These applications can improve the efficiency, automation, and robustness of CEM methods. We employ a 1-D finite-element-method scattering solver, simplifying the implementation, replicability, clarity, and intuitiveness of analysis results and conclusions, which then extend naturally to higher dimensional solvers and more complicated CEM problems. While demonstrated with a higher order solver, the derived techniques apply to low-order methodology as well. This is the first demonstration of the applicability of adjoint-based a posteriori error estimation techniques to adaptive discretization refinement in frequency-domain CEM with arbitrary-order basis functions. This work introduces the application of dual-weighted residual error estimation and selective adaptivity based on error cancellation. The proposed targeted, adaptive mesh/model p- and/or h-refinement heuristics informed by adjoint element-wise error contribution estimates show near-monotonic reduction of the quantity-of-interest error with increased numbers of refined elements. In general, adjoint techniques are underutilized in CEM, and another goal of this work is to promote their future use for refinement, optimization, and uncertainty quantification.

Large membrane “Furoshiki Satellite” applied to phased array antenna and its sounding rocket experiment

The research of millimeter wave waveguide antenna array is urgently needed by the country, but due to the limitation of insufficient processing precision of traditional processing technology, there are still some problems in the realization of large millimeter wave waveguide antenna array, which affects the national scientific and technological progress and the country’s economic development. Aiming at the realization of the large millimeter wave waveguide antenna array, this paper takes 220GHz waveguide antenna array as the research object, combining the MEMS technology that can achieve micron-level processing accuracy with the design of 220GHz waveguide antenna array, and determines the 220GHz waveguide antenna array based on MEMS technology. The design method of 220GHz antenna is simulated by HFSS. The designed 220GHz antenna has a bandwidth of 210GHz~220GHz, a gain of 31dB, a standing wave lower than 1.8, and good electrical performance. Through research, this article reveals a new implementation method for millimeter wave waveguide antenna arrays, realizes the high gain design of millimeter wave waveguide antenna arrays, and establishes a complete set of millimeter wave waveguide antenna array implementation processes, which will provide a better solution for future millimeter wave waveguide antenna arrays. The research on large arrays of waveguide antennas has laid the foundation and provided a new idea for the design of large arrays of millimeter wave waveguide antennas.

A fast non-similarity wavelet transform method, proposed earlier by the authors, is further studied. Combined with conventional techniques such as the method of moments, the boundary element method and the finite element method, the wavelet transform method can effectively handle a wide range of complicated problems which involve various complex media and conductors. The computational complexity and the CPU time for the proposed technique are presented. Studies further show that the use of non-similarity nonorthonormal cardinal spline wavelet (NS-NCSW) transform, although does not seem to reduce the computational complexity, can save a great amount of CPU time and computer memory. Numerical experiments are presented to demonstrate the merits of the proposed technique.

The Characteristic Basis Function Method (CBFM) is applied to rapidly compute the impedance and radiation characteristics of electrically large aperture-fed antenna arrays. A stationary formula for the antenna input admittance matrix is expressed in terms of a product of matrix blocks that are readily available from a method of moment formulation. Numerical results are shown for large arrays of waveguide antennas requiring more than 2 million basis functions, which is reduced by a factor of 9000, so that the solution for the currents are still obtainable in-core on a single desktop computer, while being orders faster than commercial software codes or a standard MoM approach, provided that sufficient memory is available for the Gaussian elimination.

We analyze large non-uniform optical antenna arrays of nanorods, which form optical vortices, axicons and lenses, by using a numerically efficient technique, called the Characteristics Basis Function Method (CBFM). The efficiency is realized by deriving an accurate, efficient simplified representation of nanorod, and by using the CBFM, which not only reduces the number of unknowns significantly without sacrificing the computational accuracy, but also enables us to handle large, truncated and non-uniform arrays. The method is numerically rigorous and includes all of the mutual coupling effects to obtain accurate results. Furthermore, it is readily parallelizable and can be generalized to handle more complex shapes of nanoantennas, without any difficulty.

GA-based approach to phase compensation of large phased array antennas

A non-overlapping domain decomposition method with non-matching grids for modeling large finite antenna arrays

A non-overlapping and non-conformal domain decomposition method (DDM) is presented for modelling large finite antenna arrays. There are two major ingredients in the proposed DDM: (a) A new second-order transmission condition is introduced, which improves convergence of the iterative process. In contrast to previous high order interface conditions, the new condition uses two second-order transverse derivatives to address the slow convergence issue of both TE and TM evanescent modes. Numerical experiments demonstrate that the convergence of the proposed algorithm is quite insensitive to the size of array. (b) The proposed non-conformal DDM not only permits the use of completely independent discretization for each of the sub-domains, but also allows adjacent sub-domains to be geometrically non-conformal. The benefits of the non-conformal nature of the proposed DDM will be fully enjoyed by a large-scale problem of practical interest, which is a 50 by 50 ultra wide band (UWB) array in the presence of a slot frequency selective surface (FSS). Numerical results verify the effectiveness of the proposed method.

A Sub-6 GHz band radome-covered omnidirectional horizontally polarized large spacing array antenna is reported with low grating lobe and low mutual coupling. A designed dielectric radome is utilized to replace several layers of antenna elements under the same effective aperture. The radome extends the current distribution and thus increases the effective aperture of the array element so that the array element spacing can be enlarged. Fewer antenna element is required with the radome introduced, compared with conventional spacing antenna array. Meanwhile, the large spacing decreases the mutual coupling between neighboring layers while no apparent grating lobe appears. The effectiveness of the proposed structure is evaluated by both simulation and experiment. And the mutual coupling and the grating lobe of proposed radome-covered antenna are also discussed. In the experiment, the 4-element 1-layer array model is considered. Proposed antenna is ideal for B5G application requiring fewer horizontal polarized sources covering the entire azimuth plane.

In this paper, a distribution fitting approach is proposed to estimate the angular parameters of multiple incoherently distributed sources with large antenna arrays. The estimator utilizes the approximate orthogonality of the array response vectors of large arrays to obtain a vector which is the superposition of the probability distributions of the direction-of-arrivals (DOAs) of the sources. Then, the angular parameters can be estimated by fitting distribution functions to this vector successively. Hence, the complexity of the proposed approach is much lower than that of other well-known estimators which require the fitting of a matrix. Analysis and numerical results show that the proposed estimator can achieve better performance than other estimators.

In millimeter wave (mmWave) communication systems, large antenna arrays are used to compensate high path loss. While the large array provides high beamforming gain, it also poses a challenge in channel estimation. Since mmWave channels are likely to be sparse in angular domain, the channel estimation can be converted into a sparse recovery problem, and compressed sensing (CS) can be leveraged for the channel estimation. However, conventional non-adaptive CS algorithms show poor recovery performance with low signal-to-noise ratio (SNR), which is common before beamforming in mmWave channels. Although recently developed adaptive CS schemes perform better in a low SNR regime, their excessive feedback requirement hinders practical usage. In this paper, we propose a two-stage CS scheme that requires one-time feedback and is robust to noise, which can be regarded as a compromise between the two approaches. Sufficient conditions for the support recovery with the proposed scheme are characterized, and its effectiveness is also shown numerically.

Every day on television there are weather forecast programs for several days in advance. Forecasted weather changes are obtained by analyzing and modeling the processed data collected from observing stations. One of the problems in carrying out measurements of atmospheric parameters is the tracking of a meteorological radiosonde in the air and providing two-way communication with it and the ground observing station. A new antenna system consisting of two antenna arrays is suggested for a meteorological radiosonde tracking radar. The small 4-element antenna array with a wide 35° beam switching in four directions is used in the near radar region. The small antenna array is suitable for quick target tracking at the initial stage of the weather balloon flight with high angular velocity. The large 48-element antenna array with a narrow 7° beam switching in four directions is used in the far radar region. Circular patch antennas are used as radiating elements. The large antenna array consists of eight 6-elements subarrays. The suggested design of the antenna was analyzed by using of ANSYS HFSS software. The proposed 52-element antenna system is compared with the existing one, but 24 elements larger. The paper contains the description of the antenna system and the modeling results.

The application of integral equation methods based on the method of moments discretization to solve large antenna arrays is difficult due to the fact that the computational requirements increase rapidly with the number of unknowns. This is critical when a frequency analysis of the antenna is required. We propose the multilevel matrix decomposition algorithm (MLMDA) to carry out this purpose efficiently. As the MLMDA method is particularly well-suited for the analysis of planar structures with any Green's function, it is a very efficient approach for the frequency analysis of microstrip antenna arrays.