Applied Computational Electromagnetics Society Journal (ACES)

Performance Analysis and Design Considerations of the Near-Field-Focused Rotman Lens Antennas

2024-08-18T18:27:28+02:00

This study investigates the application of Rotman lens antennas in the near field. The design equations of these antennas have been derived in the near field and demonstrated to be highly effective. By considering specific examples, the shapes of the inner surfaces of these lens antennas have been analyzed and discussed, revealing how practically realizable lens surfaces can be designed. As these Rotman lenses are perfect at only three points in the near field, they exhibit phase errors at other points along a line connecting the three near-field focal points, resulting in deterioration of the near-field patterns. It has been shown that by selecting the lens parameters appropriately, these phase errors can be kept to a minimum, causing only minimal beam deterioration. Compared to far-field-focused Rotman lens antennas, near-field-focused Rotman lens antennas achieve significantly higher power levels, having 3.8 to 6.3 dB improvement for different beams of a 17-element array. The study has demonstrated the potential of Rotman lenses as multiple beamforming antennas for near-field applications.

Design of a Radar Signature Measurement Model of an Unmanned Aerial Vehicle with Low Radar Signature

2024-04-29T21:38:35+02:00

Existing databases of RCS benchmarks lack a complex, low-observable target. This paper describes the design of such a complex and low-observable measurement model. Starting point of the design is the so-called Muldicon model, developed by the NATO/STO/AVT panel. Hot spots of the original model are identified and treated with radar-absorbing materials. Simulations on the treated model demonstrate that the model is indeed low observable. The effect of the manufacturing process of 3D-printing and separable parts is assessed experimentally on a cone-sphere; the effect is found to be negligible. These results give confidence that the model, when built, satisfies the requirements of being complex and low observable; and that artefacts of the manufacturing process will not impair its signature.

Analysis of Reader Orientation on Detection Performance of Hilbert Curve-based Fractal Chipless RFID Tags

2023-02-22T14:08:08+01:00

The role of the orientation of the radio frequency identification (RFID) reader is vital in the RFID-based communication system. This study presents the design and analysis of the impact of the orientation of the RFID reader (angle of incidence of the plane wave) on the detection and sensitivity characteristics of fractal chipless RFID tags. Four fractal (irregular) shaped tags are developed using four iterations of the Hilbert curve filling algorithm. The full-wave EM analysis of the designed tags in Matlab is performed by exporting them in Computer Simulation Technologies Micro-Wave Studio (CST MWS) in the frequency range of 2 to 20 GHz. Firstly, the performance of the tags is analyzed by observing the radar cross-section (RCS) of the tag for the fixed orientation of the incident plane wave in three different polarizations (horizontal, vertical, and oblique). Later, the variations in the EM spectrum (RCS results) are analyzed for oblique polarization by varying the incidence plane wave in both elevations (for two cases of 0^∘ and 90^∘) and azimuth planes (sweeping from 0^∘ to 180^∘ with a step size of 10^∘). The analysis of the proposed aggregated RCS response for all cases in oblique polarization produces higher coding capacity (169 bits), coding spatial capacity (16.504 bits/cm²), coding spectral capacity (9.826 bits/GHz), and coding density (0.960 bits/GHz/cm²) for the realized highly irregular tag using fourth-iteration (4T) of Hilbert curve filling algorithm. The proposed procedure of detection based on aggregated response makes the developed RFID communication system more secure and reliable.

3D Marine Controlled-Source Electromagnetic Numerical Simulation Considering Terrain and Static Effect

2024-05-20T14:40:51+02:00

The marine controlled-source electromagnetic (CSEM) method is an important geophysical method for the exploration of marine hydrocarbon resources. In marine CSEM forward modeling the uplift terrain, such as submarine hills and seamounts, the static effects caused by polymetallic nodules and hydrothermal sulfide are ignored which can lead to the deviation of marine CSEM data. To improve the accuracy of data processing and interpretation, this study realizes efficient 3D numerical simulation considering submarine uplift terrain and static effect based on the finite difference (FD) algorithm in a fictitious wave domain. First, based on the correspondence principle between the fictitious wave domain and a real diffusive domain, we derive the FD electromagnetic field iteration equations of the fictitious wave domain, and apply the fictitious emission source and the boundary condition of complex frequency shifted-perfectly matched layer (CFS-PML). We use the inverse transformation method to convert the electromagnetic response to the diffusive domain. Then, we carry out simulations on typical 1D and 3D reservoir models to verify the correctness and effectiveness of the algorithm. Furthermore, we design an uplift terrain model and a static effect model and study the influence of parameters such as top width, bottom width, height and volume of uplift terrain on the CSEM field response characteristics through the forward modeling of multiple models and discuss the influence of parameters such as electrical conductivity, length, width, thickness, depth and volume of a shallow anomaly on the marine CSEM response. Finally, we analyze the characteristics and rules of electromagnetic field propagation of uplift terrain and static effect, which provides theoretical guidance for the design of marine CSEM exploration systems.

Ultra Miniaturization and Transparency Frequency Selective Surface for Dual Band ISM Shielding

2024-08-06T19:42:18+02:00

This article presents an ultraminiaturized frequency selective surface (FSS) for shielding 2.4 GHz and 5.8 GHz (ISM) signals. The unit cell size is 0.056λ × 0.056λ (λ is the free space wavelength at the first resonant frequency). It has smaller cell size and good transparency compared to previous ISM band studies, and transparency at 54%. The proposed FSS design consists of a wall structure and a compound square loop with 2.4 GHz and 5.8 GHz resonance frequencies for ISM band coverage. This FSS structure was fabricated on float glass with a dielectric constant of 8 by a photolithographic process. The fabricated FSS structure has excellent angular stability and polarization stability, which is further verified by experimentation. An easy optimization method is proposed to tune the independent resonant frequencies by optimizing the geometries individually. This FSS is interpreted by filtering through surface induced currents and equivalent circuit models. A prototype of the proposed FSS is fabricated and measured. The simulation results are in good agreement with the measured results. The proposed FSS has polarization insensitivity and 80^∘ angle stability and is suitable for solving the EMI problem in ISM band.

An Accelerated Ray Tracing Method based on Embree3 Ray Tracing Library for Targets with Non-uniform Thickness Materials

2024-08-04T20:35:47+02:00

This paper proposes an accelerated ray tracing method utilizing the Embree3 ray tracing library for targets with non-uniform thickness materials. In contrast to the traditional surface-based ray tracing, the proposed approach performs ray tracing within the materials, since surface tracing is ineffective for materials with non-uniform thickness. To ensure efficiency and handle the overlapping grids between different materials, the Embree3 ray tracing library is introduced to ray intersection. Numerical results confirm that the proposed method surpasses existing methods in terms of efficiency and applicability while maintaining accuracy.

Efficient Electromagnetic Compatibility Optimization Design Based on the Stochastic Collocation Method

2024-04-13T10:13:21+02:00

Nowadays, in the field of electromagnetic compatibility (EMC), numerical methods such as finite element analysis are often used for simulation analysis. These numerical methods take a long time to solve some complex simulation problems, which is not conducive to the optimal design of EMC. In particular, the intelligent optimization algorithm that needs continuous iterative calculation will not be realized because of the long optimization time. This paper realizes the innovative application of the uncertainty analysis method (Stochastic Collocation Method) in EMC optimization design. Two typical EMC optimization design problems, namely, the prediction of cable crosstalk and the design of shielding performance of metal boxes, are proposed to verify the effectiveness of the optimization algorithm. Meanwhile, its performance is compared with the classical intelligent optimization algorithms such as genetic algorithms and immune algorithms.

A Spoof Surface Plasmon Polaritons Filter with Controllable Negative Slope Equalization Based on Surface Resistance

2024-08-12T09:39:06+02:00

This paper presents a novel spoof surface plasmon polariton (SSPP) filter integrated with controllable negative slope equalization. Different from traditional microwave filters, two microwave functions - amplitude compensation and interference suppression - are integrated into one device by depositing a lossy indium tin oxide (ITO) film on the rectangular corrugated stub of the SSPP unit. The key point of negative slope equalization benefits from the surface resistance of the ITO film, and the circuit model and behavior are analyzed in detail. Based on the principle, a prototype of a SSPP filter operating from S to C band is designed and fabricated. The measurement results show that the attenuation in the passband increases almost linearly from 3.5 GHz (−4.8 dB) to 6.9 GHz (−15.4 dB), indicating that −10.6 dB equalization is achieved. The improved S₂₁ is attributed to the good impedance matching by sputtering the ITO film on the rectangular metal strip rather than the central strip. Due to the natural low-pass property of SSPPs, the high-order parasitic band is suppressed above the cut-off frequency of 8.5 GHz. The analyses, simulations and measurements show that the proposed SSPP filter is provided with an additional ability to compensate for positive amplitude fluctuation in wideband antennas.

A Low-profile Dual-band Frequency Selective Surface with High Selectivity at its Higher Passband

2024-07-16T07:40:48+02:00

In order to meet the requirements for multiband communication, a dual-band passband frequency selective surface (FSS) with low-profile and high selectivity at its higher passband is proposed in this paper. The proposed FSS is a three-layer structure. An arc-cross patch (ACP) and four quarter-circular patches (QCP) are introduced on the outer layers to produce two transmission nulls of the higher passband, which result in high selectivity of higher passband. The inductively complementary structure on the middle layer is introduced to manipulate the coupling between layers which contribute to the low-profile and angular stability. The segmental study method is used to establish the equivalent circuit model (ECM) and analyze its mechanism. The proposed dual-band FSS, whose high selectivity was verified by experiment, is low-profile and shows good polarization insensitivity and angular stability. A feasible FSS design solution is provided for dual-band communication.

Comparative Study of High-speed Permanent Magnet Synchronous Motors with In-line Slot Conductors and Equidirectional Toroidal Windings

2024-06-09T13:21:16+02:00

The high-speed permanent magnet synchronous motor (HSPMSM) plays an important role in a wide range of engineering fields due to its high power density, high efficiency, and light weight. In this paper, a HSPMSM equipped with in-line slot conductors(I-LSC) is proposed and compared with one equipped with equidirectional toroidal winding (ETW). Firstly, the differences between them are revealed, including topology, back-electromotive force (EMF), slot fill factor, copper loss, and torque. Secondly, two-dimensional finite element method (2D-FEM) tools are used to obtain more precise performance such as air-gap field, back-EMF, torque characteristics, efficiency maps, and the unbalanced magnetic force (UMF). Considering the end-windings of copper loss of ETW and the end ring copper loss of I-LSC, the losses and efficiency of two motors are simulated by three-dimensional finite element method (3D-FEM). Finally, the simulation results validate the feasibility of the newly proposed winding and indicate that in-line slot conductors have superiority in power density due to the high slot fill factor.