International Journal of RF and Microwave Computer-Aided Engineering最新文献

In this work, we propose a physics-informed extreme learning machine (PIELM) method to identify the eigenmode field distributions of waveguides and transmission lines by solving Helmholtz partial differential equation (PDE) with initial and boundary conditions. A single-layer neural network architecture is adopted in PIELM, where the input layer parameters are initialized randomly. By embedding physics-informed constraints into the loss function, a system matrix equation can be established. Then, the output layer weights can be learned with the Moore–Penrose generalized inverse algorithm. Compared with physics-informed neural network (PINN), PIELM only uses a single-layer feedforward neural network and does not engage in an iterative optimization process utilizing backpropagation and gradient descent algorithms. As a result, the time spent on model training is reduced significantly, with the total process accelerated. Some numerical examples are presented to validate both accuracy and efficiency of PIELM method compared with PINN method in solving the eigenmode field distribution problem of waveguides and transmission lines.

This paper presents an improved design of a Ku-band power divider (PD) based on a substrate integrated waveguide (SIW) technology. The design is aimed at using the block upconverter (BUC) of the Ku-band satellite communication system. The PD has been developed to operate in the frequency range of 13.75–14.5 GHz for low-loss, good isolation, and good amplitude and phase imbalances for both power dividing and combining. To increase the isolation between output ports, TE₁₀₂ mode is selected to operate in the main cavity while the coupled cavity operates in the TE₁₀₁ mode. Low insertion loss of the PD can be achievable by determining Q factor of the SIW cavities. In addition, good phase and amplitude imbalances can also be obtained by making a suitable arrangement of the input and output ports. The measured results at the center frequency of 14.12 GHz exhibit an insertion loss of 1.3 dB, return loss of 16.9 dB, isolation of 16 dB, amplitude imbalance of 1.2 dB, and phase imbalance of 2.8°. The simulations are consistent with the measurements, validating the accuracy of the proposed method. The proposed PD can be a promising candidate for use in the BUC of the Ku-band satellite systems.

This work presents a multiple-input/multiple-output (MIMO) antenna consisting of dipoles with integrated baluns and a parasitic element to reduce mutual coupling, which can cover two frequency bands. The configuration of the decoupling element is determined by using an optimization algorithm. The algorithm takes nine physical dimensions of the decoupling element as input and adjusts them by minimizing a cost function. One of these decision variables (DVs) is the number of decoupling element’s stairs (steps), which is a discrete parameter. In its simple form, the antenna cannot obtain proper isolation in the low-frequency band, which has been solved by employing a decoupling structure in the middle of the antenna. The experimental results show that the antenna has impedance bandwidths of 1.95–3.50 GHz and 3.98–5.67 GHz, providing minimum isolation of 13.1 and 19.5 dB in the low- and high-frequency bands, respectively. The ECC value is lower than 0.0038, and the peak gains are equal to 4.4 and 5.21 dB for the low- and high-frequency bands. The main contribution of this work is the design of the decoupling element, which, considering the antenna’s characteristics, has improved the antenna’s isolation by 12.4 dB only in the center of the low-frequency band.

A compact ultralow-profile wideband and high-efficiency folded transmitarray antenna (FTA) is proposed in this letter. It consists of three parts: a top transmission surface (TS), a bottom reflection surface (RS), and an embedded compact planar feed. Using the principle of ray tracing and introducing additional phase compensation in the RS, the antenna profile can be significantly reduced, leading to a profile-to-diameter ratio (H/D) of only 0.13. Despite such an ultralow profile, the antenna overall performance still remains satisfactory. For design concept validation, a compact and ultralow-profile FTA is designed and prototyped. Measurement results demonstrate that the peak aperture efficiency of the FTA is 36%, with 1-dB/3-dB gain bandwidth of 10%/20%, respectively. These appealing characteristics make the proposed design very suitable for various high-gain applications where a low-profile and compact configuration is required.

In this paper, a compact dual-band antenna module has been developed, achieving significant isolation between the ports. The design integrates an open-edge slot antenna for the lower frequency band (5.15–7.1 GHz) with a 1 × 2 MIMO metasurface antenna for the mmWave frequency range (24.5–29.5 GHz), resulting in a high-performance, compact dual-band solution. The slot antenna is optimized for a reduced size configuration with enhanced bandwidth for lower frequencies, while the metasurface antenna delivers wider bandwidth and stable performance in the mmWave range with minimal mutual coupling and high efficiency. This makes the overall design highly effective for modern compact dual-band applications. The dual-band antenna module has dimensions of 20 × 16.5 × 0.99 mm (0.39λ₀ × 0.32λ₀ × 0.01λ₀, where λ₀ represents the free-space wavelength at 5.85 GHz). It achieves a measured peak gain of 3.8 dB for the lower band and 8.81 dB for the mmWave band. Additionally, the output of the mmWave antennas can be combined for higher gain or used in a MIMO configuration, enhancing channel capacity and communication reliability, which are critical for modern wireless systems.

Aiming at the electromagnetic compatibility testing requirements of slender equipment, this paper proposes a design scheme for a cylindrical reverberation chamber. Through numerical simulation, the lowest usable frequency and field uniformity of the cylindrical reverberation chamber were analyzed. The results show that the cylindrical reverberation chamber has good field uniformity when the frequency is greater than $$, meeting the stringent requirements of IEC 61000-4-21. Utilizing this cylindrical structure for the reverberation chamber can effectively reduce testing costs and improve testing efficiency and accuracy. This research provides a foundation for further optimization of cylindrical reverberation chamber design, and it is expected to become an important tool for effective electromagnetic compatibility testing of equipment.

The domain decomposition method (DDM) enables efficient simulation of electromagnetic problems in large-scale array antennas using full-wave methods on moderate hardware. This paper introduces and compares two nonoverlapping DDMs serving as preconditioners with outstanding simulation efficiency. The first method targets finite periodic array antennas by transforming a single array unit rather than explicitly modeling the entire array, effectively leveraging repetitive structures to significantly reduce memory usage and computation time. The second method applies to universal array antennas with arbitrary geometries, employing both planar and nonplanar mesh-based domain partitioning at subdomain interfaces for flexible modeling of complex arrays. To further enhance computational performance, we propose a parallel multilevel preconditioner based on the block Jacobi preconditioner, thereby accelerating the solution efficiency of subdomain matrix equations in both methods. Additionally, since the choice of domain partitioning method significantly impacts the computational efficiency of DDMs, we propose three different subdomain partitioning strategies. These strategies enable us to accelerate computations while expanding our capacity to simulate a wider variety of types of cases. We developed a fast electromagnetic radiation simulation tool utilizing these techniques. Simulations of exponentially tapered slot (Vivaldi) antenna arrays and antenna arrays with radomes demonstrate that our tool achieves accuracy comparable to commercial software, and notably, our tool outperforms commercial software in terms of the speed of iterative solutions.

In this paper, a new coating structure is proposed for broadband radar cross section (RCS) reduction using 1-bit metasurfaces. The designed structure consists of two types of unit cell, arranged in concentric square rings. The substrate of unit cells is different, FR4 and Ultralum-2000 with thicknesses of 2.4 and 0.762 mm, respectively. The proposed structure shows an ultrawideband property to reduce the RCS, less than −10 dB, in the frequency range of 14–45 GHz. This range covers part of Ku-band (14–18 GHz), K-band (18–27 GHz), and Ka-band (27–40 GHz) and part of millimeter-wave band (40–45 GHz). To validate the designed work and simulation results, a prototype with the dimension of 84 × 84 mm² is fabricated and tested. Also, the RCS reduction is determined analytically and presented. The measured results verify well the analytical and simulation results. In short, this work includes three new points: (1) the use of two substrates with different thickness and dielectric constant to design unit cells, (2) a new arrangement of array cells in the form of concentric square rings, and (3) achieving a great bandwidth to reduce RCS.

The use of surrogate models in assisting evolutionary algorithms for antenna optimization has achieved significant research outcomes. The construction of surrogate model primarily depends on two aspects; one is the selection of datasets, and the other is the model’s structure and performance. This paper proposes a novel dataset selection method aimed at enhancing the performance of the constructed surrogate model. Additionally, based on Bayesian neural network (BNN) and leveraging the advantages of handling sequence data with long short-term memory (LSTM), a BNN-LSTM surrogate model is introduced. After training, this surrogate model is used as the fitness evaluation function, enabling optimization design based on differential evolution (DE) algorithm. Experimental validations are conducted using the optimizations of a dual-frequency slotted patch antenna and a rectangular cut-corner ultrawideband antenna as examples. Results demonstrate that the proposed surrogate model exhibits high accuracy, providing a guidance for antenna optimization.

A spaceborne Earth-coverage phased array (ECPA) antenna at Ka-band is proposed for low-Earth orbit (LEO) satellite applications, which is based on digital beamforming (DBF) partially shared subarray architecture to implement two stages of DBF. By taking into account the effects of mutual coupling in active element pattern optimization, a new method to obtain an Earth-matched beam of the equivalent element of the ECPA is presented, in which the DBF-shared subarray, segmental shaping technique, and differential evolution algorithm are utilized to achieve Earth-coverage characteristic for the ECPA. Both the design method and the principle of DBF partially shared subarray for grating lobe suppression are presented. Moreover, a 16-element DBF-shared subarray with a shared ratio of 4:1 obtaining an Earth-matched beam pattern is designed, optimized, and verified by full-wave simulation in Ansys Electronics Desktop. Taking the DBF-shared subarray as the equivalent element, an ECPA including 40 DBF-shared subarrays is also designed and simulated. Numerical results demonstrate that the proposed ECPA has excellent performance of Earth-coverage scanning to compensate for the satellite communication link variation caused by path loss variation during beam scanning for LEO applications. In addition, the ECPA has the advantages of a low sidelobe level better than −20 dB as well as grating lobe suppression.