Applied Computational Electromagnetics Society Journal (ACES)

Introduction to the Special Issue

2026-05-07T05:00:45+02:00

Welcome to the special issue of the Applied Computational Electromagnetics Society (ACES) Journal. This special
issue brings together a collection of state-of-the-art research findings aimed at advances in next-generation antenna
systems and their testing methods.
The special issue covers the following topics
• Microwave and millimeter-wave antenna arrays
• Reconfigurable intelligent surfaces
• Reflectarray and transmitarray
• Mutual coupling role in antenna arrays
• Antenna diagnosis and measurements methodologies
• Over-the-air tests
We’d like to also thank the Editors in Chief of ACES Journal, Professor Sami Barmadi and Professor Atef Elsherbeni
for their support. And we’d like to express our thanks to the editorial and publication team at ACES Journal for their
assistance.

Low-Loss 16-Way Ultra-Wideband Wilkinson Power Divider

2025-09-22T18:48:28+02:00

Several power divider designs exist in the literature and are also commercially available. However, these dividers are not wideband. In this paper, a low-loss, ultra-wideband (UWB) 16-way power divider for UWB applications is presented. Notably, the design employs 15 cascaded multi-stage Wilkinson power dividers with a total of 90, 0402 package surface mounted chip resistors to enable operation from 0.2 to 3.6 GHz. Remarkably, the fabricated prototype achieves an 18:1 input and output impedance bandwidth with VSWR<1.2 thanks to an optimization approach that eliminates any additive reflection from each of the power division stages. In addition, the maximum insertion loss is 3 dB at the highest frequency of operation, while the maximum phase imbalance between output ports is 4 degrees. The measurements show excellent agreement with the simulations.

A Phase Center Estimation Method for Automotive Antenna Measurements

2025-11-21T22:17:26+01:00

This paper presents a blind phase center estimation method for hemispherical near-field automotive antenna tests. The previous method only satisfies the less edge-scattering affected conditions, whose phase center estimation stability and accuracy are not satisfactory. While, the newly proposed method utilizes image theory as filtering process to characterize the electric fields with reduced edge-scattering effects, and the phase center is more accurately derived by the local searching strategy combined with a fast least-squares-based method along the x-, y- and z-axis. Correspondingly, the improvement of the calibrated pattern is significant. The simulation and measurement results both demonstrate the superiority of the proposed method with less time cost and better accuracy for different types of automotive antennas than the previous method. More importantly, the proposed method does not need to distinguish the edge-scattering-affected condition and non-edge-scatteringaffected condition, which will lead to an easy work for estimating the phase center and ensure the accuracy of the pattern offset calibration.

Experimental Assessment of a Non-Redundant Approach to Minimize Data in a Spherical NF-FF Transformation for Offset Mounted Elongated AUTs

2025-07-14T18:58:29+02:00

This work concerns the experimental validation of a near-field (NF) spherical scanning for an offset mounted long antenna under test (AUT), that requires a non-redundant (NR), namely minimum, amount of NF data. We address the issue of decreasing the number of voltage samples required to execute the traditional NF-far-field transformation (NF-FFT) technique in a non-centered case scenario, which would generally need a considerably higher amount of input data as compared to the onset case. In particular, by exploiting the theory of the NR sampling representations of electromagnetic field and adopting a rounded cylinder model of the antenna, the number of required samples is exactly the same as the minimum one involved in the onset scenario. Experimental results, which prove the goodness and efficacy of the approach, are presented.

A Hybrid Efficient Iterative ACA-PO and Chebyshev Approximation Technique for Fast Radiation Analysis Over a Broad Frequency Band

2025-06-10T18:16:14+02:00

In this paper, a novel approach integrated efficient iterative adaptive cross approximation-physical optics (EI-ACA-PO) and Chebyshev approximation technique (CAT) is proposed to efficiently calculate the broadband solution of antenna placed on electrically large platforms. The adaptive cross-approximation (ACA) method is employed to compress the self-impedance matrix of the Method of Moments (MoM) region, and the interaction matrices between the MoM and physical optics (PO) regions. By introducing CAT technology, the iterative hybrid method is capable of efficiently calculating the wideband results. First, the outer surface is divided into two regions. Then, the integral equation is solved by the EI-ACA-PO method to obtain the induced current at the Chebyshev nodes. Afterwards, the current in a desired frequency band is represented by the Chebyshev series. To improve accuracy, the Chebyshev series is matched with the Maehly approximation. The current at any frequency point in the bandwidth can be calculated. Finally, the broadband electromagnetic radiation characteristics can be obtained.

A Single-Layer Reflectarray Unit Cell with Enhanced Performance Using Dual Concentric Split-Circle Rings

2025-10-20T17:38:00+02:00

This paper proposes a dual-ring unit cell design for a single-layer reflectarray antenna. The element is attained using two concentric split-ring resonators, where each ring is divided into four equal sections. By adjusting the width, scaling, and radius of the concentric split-rings, two distinct resonance frequencies are realized in each ring, attributable to the electric length inside the rings. This approach yields a wider phase range for the reflection coefficient, with a nearly linear phase response. Three different configurations are investigated to identify the best performance parameters. The electromagnetic behavior of the proposed unit element is simulated using CST Microwave Studio Suite. The reflection characteristics are analyzed using the infinite-array model with Floquet port excitation. Hexahedral meshing is employed for the antenna configuration, with the mesh density adjusted according to the wavelength to validate sufficient resolution of the structural features. The unit cell was also investigated using the HFSS frequency-domain solver based on the finite integration technique. An equivalent circuit was found using the Advanced Design System (ADS). The simulation results indicate that all three configurations offer a broad phase variation, with the minimum phase of approximately 885∘ at 10 GHz in case 2, and a maximum phase slope of 68∘/mm at 12 GHz in case 1, over the 8–12 GHz frequency range. The configuration in case 3 achieves the widest operational bandwidth of 26.8% centered at 10 GHz.

A 3 dB Coupler With Defected Ground Structure for Feeds Applied to High-Power Intelligent Metasurface

2025-08-19T21:40:13+02:00

This paper proposes a 3 dB coupler with high-power handling capability feeds applied to high-power intelligent metasurface, based on loosely coupled structures and defected ground structure (DGS). The proposed coupler structure consists of two tandem coupled couplers with a coupling coefficient of 8.34 dB and a DGS, a design that significantly enhances the couplers’ ability to handle high power levels. The measurement results are in good agreement with the simulation results: within the 3.5 to 4.5 GHz range, the return loss exceeds 21.4 dB, the isolation is at least 20.8 dB, the insertion loss is less than 0.3 dB, and the phase difference between output ports is 93–94.5^∘. Furthermore, the coupler can handle high power exceeding 1.5 kW with a 10% duty cycle. The proposed 3 dB coupler features low insertion loss, high isolation, low return loss, high-power capability, and can improve the power capability of intelligent metasurface systems.

Wideband Dual-Polarized Metasurface Antenna Array with High Isolation

2025-12-05T19:32:09+01:00

This paper presents a dual-polarized 1×4 antenna array with wide bandwidth and high isolation. The antenna element consists of three metallic layers, a 4×4-unit metasurface (MTS) on the top layer, a patch fed by two ports on the middle layer, and a ground plane on the bottom layer. By exciting different feeding ports, the antenna achieves X-axis linear polarizations (X-LP) or Y-axis linear polarizations (Y-LP). Isolation slots etched on the patch, combined with a via-hole structure, effectively block the coupling between ports and improve port isolation. Experimental results demonstrate that the proposed antenna achieves an impedance bandwidth of 17.4% (4.975–5.925 GHz), with S₁₁<−10 dB and S₂₁<−20 dB. The measured peak gain attains 12.5 dBi.

A V-Band Magnetoelectric Dipole Filtering Antenna Based on Rectangular Micro-Coaxial Lines

2025-08-19T21:37:20+02:00

A high-selectivity filtering magnetoelectric (ME) dipole antenna based on rectangular micro-coaxial lines (RMCLs) is presented, fabricated using micro-metal additive manufacturing (M-MAM) for V-band operation. The structure integrates two λ/4 resonators, one λ/2 resonator, and an ME dipole antenna, coupled through J/K-inverters realized as RMCL gaps and short-circuited stubs. Notably, while a standalone ME dipole inherently supports an impedance bandwidth over 30%, this design achieves a 5.04% operating bandwidth centered at 59.5 GHz after integrating filtering functionality. Simulations confirm a peak gain of 4.53 dBi within the passband, with cross-polarization consistently below −20 dB. A sharp gain roll-off to −10 dBi at 1.048f₀ and 40 dB out-of-band suppression demonstrates exceptional frequency selectivity. Owing to inherent miniaturization, lightweight construction, and low-loss characteristics, the antenna exhibits significant potential for low-earth-orbit (LEO) satellite internet systems.

An S-Band Low-Probability Intercept Radar Antenna With Low Sidelobe Level

2025-08-19T21:34:15+02:00

A half-wave dipole array antenna design for S-band low probability of intercept (LPI) radar is presented. The antenna structure comprises 24×2 linearly polarized dipole elements. A 24-column Taylor distribution weighted feed in the azimuth plane realizes low sidelobe level (SLL) of −26.0 dB. The antenna achieves an operational bandwidth of 100 MHz with a voltage standing wave ratio (VSWR) below 1.4. A prototype was fabricated and measured for verification. The measured gain is 22.3 dBi, with half-power beamwidth (HPBW) of 6.5^∘ and 24.5^∘ in azimuth and elevation, respectively. Results show that the array scans from −45^∘ to +45^∘ with a gain loss below 2.1 dB, while maintaining an SLL under −20.2 dB across this wide scanning range.

Figures of Merit Analysis for Over-the-Air Testing of the Non-Terrestrial Network Direct-to-Smartphone Handsets

2025-11-07T16:48:58+01:00

The Non-Terrestrial Network (NTN) is a critical component of the 6G integrated space-air-ground-sea network. The comprehensive Over-the-Air (OTA) performance evaluation of NTN terminals is essential for ensuring wireless connection reliability and quality of experience. However, major international standards bodies including 3rd Generation Partnership Project (3GPP) and Cellular Telecommunications and Internet Association (CTIA) remain in the preliminary stages of developing their OTA specifications for mobile terminals supporting NTN communications. Accordingly, the objective of this paper is to investigate key Figures of Merit (FoMs) for OTA testing of NTN handsets from the perspective of satellite coverage multiplicity, to better characterize, distinguish, and rank OTA performance of different NTN handsets for future testing methodology development. During the analysis, coverage models are created for Low Earth Orbit (LEO) and Geosynchronous Orbit (GEO) constellations separately, based on which the coverage multiplicity for Starlink Direct-to-Cell (DTC) and TianTong-1 constellations is evaluated and determined for different target regions quantitatively. By comparing the coverage multiplicity and usage scenarios with those of the Global Positioning System (GPS), whose OTA FoMs and testing methods have been clearly defined in specifications, the FoMs for OTA testing of NTN handsets are recommended, including integrated FoMs for LEO (e.g., Total Isotropic Sensitivity [TIS] and Upper Hemisphere Isotropic Sensitivity [UHIS] metrics for receiver performance, and Total Radiated Power [TRP] and new Upper Hemisphere Radiated Power [UHRP] metric [corresponding to the UHIS] for radiation performance evaluation) as well as directional FoMs (e.g., requiring the average or minimum of Effective Isotropic Radiated Power [EIRP] and Effective Isotropic Sensitivity [EIS] values within a specific zenith angular range to exceed the limit) for GEO constellations, respectively.

Design of Wideband High Out-of-Band Suppression Filtering Antenna Based on Multi-Lobe Dipole Structure

2025-07-30T23:16:56+02:00

A two-layer filtering antenna based on a multi-lobe dipole structure is presented in this paper. Parasitic substrates and vertical copper elements are incorporated between the upper and lower substrates, with impedance matching improved by overcoming the closed magnetic flux limitation. Filtering performance is achieved through interaction with semi-circular-rectangular dual-mode matching structures and vertical metal, the composite structure can generate reverse current distribution. As a result, high-roll-off radiation nulls are formed and frequency selectivity is enhanced. In order to simultaneously enhance out-of-band suppression, high-current etching technology is employed to reconstruct the current path, etching semi-circular-rectangular dual-shape composite matching structures on the radiation patch, thus a significant improvement in gain stability is achieved. Distributed current control technology is utilized to decompose the dipole into multiple lobes, ensuring uniform current distribution and reducing concentration effects. Etched rectangular holes in the surrounding electromagnetic shielding isolation walls help reduce cross-polarization by suppressing surface waves and edge diffraction. The design achieves an impedance bandwidth exceeding 36%, out-of-band suppression exceeding 32 dB, a peak gain of 8.9 dBi, with cross-polarization levels below -30dB and -26dB in the E- and H-planes, respectively.