The Applied Computational Electromagnetics Society Journal (ACES)

A Passive Adaptive Metamaterial Radome based on PIN Diodes

2023-12-11T10:34:31+01:00

Automatic protection of EM detecting systems from unexpected high-power incidence is important to the robustness and life of a passive detecting system. In this paper, an adaptive metamaterial radome which automatically shields the receiving antenna from strong incident wave is designed. Based on standard wire medium, PIN diodes are added between adjacent wires. When the incident EM wave is weak, the diodes are in “off” state and affect little to the transmission of the wire medium. When the incident EM wave is strong enough to turn the diodes to “on” state, electric currents will be automatically formed in the diodes and the power transmitted to the antenna will be largely reduced. The adaptive transmission of the proposed radome is validated by the simulation and measurement results.

Uncertainty Quantification and Optimal Design of EV-WPT System Efficiency based on Adaptive Gaussian Process Regression

2023-07-20T09:08:11+02:00

Wireless power transfer (WPT) is a safe, convenient, and intelligent charging solution for electric vehicles. To address the problem of the susceptibility of transmission efficiency to large uncertainties owing to differences in coil and circuit element processing and actual driving levels, this study proposes the use of adaptive Gaussian process regression (aGPR) for the uncertainty quantification of efficiency. A WPT system efficiency aGPR surrogate model is constructed with a set of selected small-sample data, and the confidence interval and probability density function of the transmission efficiency are predicted. Finally, the reptile search algorithm is used to optimize the structure of the WPT system to improve efficiency.

Mitigation of Feed Horn Overlapping Condition for Multi-beam Parabolic Reflector Antenna

2024-01-14T11:07:30+01:00

In designing a contoured beam for communication satellite services, a reflector antenna remains the most preferred option. Previously, a multi-beam technique employing many feed horns at optimal feed positions was proposed to obtain a precise contour beam for Malaysia. However, it has led to feed horn overlapping when the beams were arranged closely. Therefore, this issue of beam allocation and feed horn size shall be addressed. In this article, an analysis of the relationship between feed position and beam direction is analysed through the Beam Deviation Factor (BDF). As a result, a useful design chart was derived for no feed horn overlapping conditions, which determines beam separation and feed horn size at different values of F/D. A practical application showing the Peninsular Malaysia beam coverage was demonstrated to validate the derived correlation. As a result, five multi-beams have been successfully designed with no overlapping feed horns. Through simulation, an excellent contour beam for Peninsular Malaysia was justified, featuring low side lobes, narrow beam width and high gain.

Inductive Reactance Isolated Dynamic Seawater Monopole Antenna of High Efficiency

2023-12-11T09:56:46+01:00

The dynamic-type seawater monopole antenna has the problem of direct connection between its radiation body and the seawater. This makes the radiation current flow into the seawater, which leads to low radiation efficiency. In this paper, a dynamic-type seawater monopole antenna of high efficiency is proposed using an inductive reactance isolated method. Based on this method, a dynamic seawater antenna of seawater inductance isolation structure is designed. According to its equivalent circuit diagram, the principle and design basis of isolation are analyzed. The FEKO software is then used to simulate the antenna’s radiation efficiency. In addition, the impacts of the radius of the seawater inductance, the number of turns of the seawater coil, the diameter of the seawater coil, and the average turn spacing on the efficiency of the antenna are studied. Moreover, the experimental verification shows that the radiation efficiency of the designed dynamic seawater antenna with inductive reactance isolation structure can be greater than 70%. The value of the received carrier power in the case of inductance isolation is higher by 10 dB compared with the case without isolation.

Design of Wilkinson Power Dividers with SITL Compensated Microstrip Bandpass Filters

2024-02-04T15:53:18+01:00

This paper presents a simple technique for improving performances of a conventional Wilkinson power divider. The technique is achieved by replacing bulky quarter-wave transmission lines with stepped impedance transmission lines (SITL) compensated coupled lines. With the internal function of bandpass filter integrated with the proposed coupled lines, the spurious response at 2^nd harmonics frequencies that normally exists in the conventional divider is considerably reduced. Simulated and measured results at 2.1 GHz operating frequency of the proposed and conventional Wilkinson power divider were compared. The proposed divider achieves -3.8 dB insertion loss (S₂₁,S₃₁) and more than 25 dB return loss (S₁₁,S₂₂,S₃₃) across 10% fractional bandwidth. Based on this measurement, the proposed circuit achieves more than 34.5 dB suppression at the 2^nd harmonic frequency.

A Symmetrical Fractal-based Balanced Branch-Line Coupler for Simultaneous Low- and Mid-band 5G Frequencies Applications

2024-01-09T08:15:52+01:00

Symmetry is a key factor for Branch-Line Couplers (BLCs) in RF and microwave systems. This balanced approach evenly distributes power between two output ports, aiding impedance matching and reducing unwanted coupling and crosstalk, while increasing input-output isolation. Furthermore, the symmetrical design of BLCs ensures favorable return loss and phase balance, which are essential for phase-sensitive detectors and beamforming. This symmetry also guarantees consistent performance over a wide frequency range, making it suitable for broadband or multi-frequency applications. We present a compact BLC operating in two frequency bands, ideal for 5G sub-6 GHz applications. It uses T-shaped lines with folded lines and stubs in a Minkowski fractal shape, resulting in a size reduction of 90%. The design and simulation were performed using the CST Microwave Studio at 0.7 GHz and 3.5 GHz, achieving a new high frequency band ratio of 5. A prototype on Rogers RT5880 substrate (ε_r=2.2,h=0.787 mm) was tested to validate the design’s effectiveness, offering potential for modern wireless applications requiring versatile frequency band operation.

Single-mode Condition and Bending Loss Analysis of Ultrafast Laser-inscribed Mid-infrared Waveguides in GeAsSe Chalcogenide Glass

2024-01-25T10:29:06+01:00

In this study, single-mode conditions and bending losses of optical waveguides based on Ge₃₃As₁₂Se₅₅ chalcogenide glass, commercially known as IG2, for astrophotonic devices in the mid-infrared spectral range are numerically analyzed. The scalar finite-element method was used to analyze single-mode conditions. For the bending-loss analysis, equivalent straight waveguides of bent waveguides were analyzed using the two-dimensional finite-difference beam-propagation method. The results revealed design rules for astrophotonic optical integrated circuits in the mid-infrared spectral range.

An Investigation of the Relationship between Effective Relative Permittivity and Infill Density in a 3D Printed Slab

2023-09-06T11:28:13+02:00

This paper presents a simulation-based study on the relative permittivity of 3D printed dielectric slabs printed with varying infill densities. In this study, a percentage volumetric model has been employed to model the infill density in a 3D printed dielectric slab. The relative permittivity of the filament material used to design the slab is assumed to be 2.45. The modeled slab is fitted into various rectangular waveguides with varying dimensions corresponding to different frequency ranges. As the infill density decreases, the relative permittivity of the dielectric slabs decreases. This lower value of relative permittivity is referred to as effective relative permittivity (εr.eff) throughout the paper. The study concludes that the effective relative permittivity of the slab decreases linearly as the infill density is decreased for the model. This study offers valuable insights into the effective relative permittivity of dielectric slabs under varying infill densities, providing implications for applications in areas such as antenna design.

Resonant Frequency Modelling of Microstrip Antennas by Consensus Network and Student’s-T Process

2023-12-07T21:31:35+01:00

When modelling and optimizing antennas by machine learning (ML) methods, it is the most time-consuming to obtain the training samples with labels from full-wave electromagnetic simulation software. To address the problem, this paper proposes an optimization method based on the consensus results of multiple independently trained Student’s-T Process (STP) with excellent generalization ability. First, the STP is introduced as a surrogate model to replace the traditional Gaussian Process (GP), and the hyperparameters of the STP model are optimized. Afterwards, a consistency algorithm is used to process the results of multiple independently trained STPs to improve the reliability of the results. Furthermore, an aggregation algorithm is adopted to reduce the error obtained in the consistency results if it is greater than the consistency flag. The effectiveness of the proposed model is demonstrated through experiments with rectangular microstrip antennas (RMSA) and circular microstrip antennas (CMSA). The experimental results show that the use of multiple independently trained STPs can accelerate the antenna design optimization process, and improve modelling accuracy while maintaining modelling efficiency, which has high generalization ability.

Multi-polarized Reconfigurable Antenna with Ground Plane Slot and Capacitance Feeding for UAV-to-everything Communications

2023-12-27T06:43:23+01:00

This paper proposes a polarized reconfigurable antenna for unmanned aerial vehicles (UAVs) with flexible UAV-to-Everything (U2X) communications through a reduction of polarization loss. It operates at 2.45 GHz and consists of a square patch antenna, a capacitance feed, a ground surface slot, and a reconfigurable feeding network. The reconfigurable feeding network has dual polarization (linear, circular) depending on the configuration of the feeding network. The dual linear polarization reconfigurable feeding network configuration consists of a single-pole double-throw (SPDT) switch, a 50-ohm microstrip line, and a low-temperature co-fired ceramic (LTCC) 90-degree hybrid coupler. This was added to the circuit to form a double circular polarization reconfigurable feeding network. The proposed antenna has a miniaturized size (0.389λ_o×0.389λ_o×0.005λ_o), and is lightweight (12.2 g), making it suitable for low-height flight. Furthermore, it has maximum gains of 6.6 dBi and 7.2 dBi, in addition to an efficiency of 82%, and a 10 dB bandwidth of 4.5% (2.38-2.49 GHz). Therefore, the proposed antenna covers all UAV control links, video, and telemetry frequency bands (2.38-2.485 GHz).