Iet Microwaves Antennas & Propagation最新文献

The study presents the design and development of a plasma-based antenna array system for the UHF band. The system features an omnidirectional plasma antenna as its active radiator, a novel approach that has not been previously explored. Surrounding plasma reflectors around the plasma antenna form a reconfigurable array. The plasma antenna is the only radiating element in the array, whereas the surrounding plasma reflectors enhance the gain and directivity of the array, facilitating beam shaping and steering. This new design creates a fully plasma based system enabling dual reconfigurability in frequency and radiation pattern. Electronic beam scanning is possible in the azimuthal plane from 0° to 360° in 18° steps. The resonance frequency of the array is optimised to 820 MHz, resulting in a significant increase in plasma antenna gain from −5 to 0 dB within the operating frequency range. Activating the plasma reflectors reduces cross polarisation by 20 dB. The proposed array achieves a 25 dB front-to-back ratio and a bandwidth of 600 MHz. The array's RCS varies from 6 $��{\text{dBm}}^2�$ to $��-�30�$ $��{\text{dBm}}^2�$ over the 1–12 GHz range, rendering it invisible from 8 to 12 GHz. This plasma-based array is suitable for radar, defence and navigation systems.

To meet various customised requirements for RF devices efficiently, a fast artificial intelligence (AI)-driven design method is proposed using a physically inspired forward solver with coupling matrix via the artificial neural network (ANN). Establishing the space mapping from the coarse model to the fine model through ANN enables the rapid and accurate acquisition of a large number of S-parameters of the filter under different geometric parameters. To improve the construction efficiency and performance of the forward solver, the mutual coupling matrix of the resonator (M matrix) is extracted from the S-parameters obtained as input of the surrogated model, which exhibits better robustness, convergence and training efficiency. Furthermore, by integrating with the AI-driven forward solver, the performance of the RF devices could be efficiently optimised according to the requirements with the heuristic algorithms. Simulation, comparison and experimental results all demonstrate that the designed RF filters and filter antennas accordingly exhibit high efficiency and excellent prediction accuracy at various operating frequencies and bandwidths, thus proving the effectiveness and practicality of the proposed optimisation method.

This article presents the design, fabrication and experimental validation of a compact linear series-fed microstrip antenna array with dual circular polarisation (CP) capability. The proposed structure consists of a $��4�\times �4�$ slotted circular patch array excited via four microstrip lines using a coplanar proximity coupling technique. Dual-CP operation is achieved through two miniaturised and distinct microstrip power divider networks, enabling the generation of either left-hand or right-hand CP based on the excitation port. To maximise gain and efficiency, the design reduces feedline branching and employs optimised slotted patch elements, resulting in low power loss and high radiation efficiency. The antenna achieves a realised peak gain of 19.4 dBic across 12.2–12.7 GHz and a 3-dB axial ratio bandwidth from 11.9 to 13.1 GHz. Simulation and measurement results demonstrate excellent agreement. Thanks to its compact size, wide bandwidth, dual-CP functionality and high gain, the proposed antenna offers a promising solution for point-to-point wireless communication systems. Compared to existing multi- and single-layer microstrip-based CP arrays, this work introduces a simplified feed structure and improved performance, demonstrating clear advancement in antenna array design.

Emerging programmable metasurface technologies enable flexible manipulation of electromagnetic waves. However, the instantaneous design of corresponding code sequences remains a challenging problem. In this paper, a fast and reliable coding strategy for 1-bit programmable metasurfaces is proposed. Under the assumption that the reflection amplitudes for both ‘0’ and ‘1’ coding states are equal to unity, the original coding problem is first formulated as a linear inverse problem. Since the phase difference between ‘0’ and ‘1’ coding states is approximately $��\pi �$, such a prior information is then exploited for addressing the linear inverse problem. Specifically, a hierarchical truncated Gaussian mixture (TGM) prior model is adopted to account for the feature of the unknowns. Moreover, the variational expectation maximisation (VEM) along with the generalised approximate message passing (GAMP) is used for Bayesian inference, significantly reducing the computational complexity. Several numerical examples are presented to illustrate the potential of the proposed coding scheme.

This paper presents the design, simulation and fabrication of a wideband Wilkinson power divider (WPD) based on ridge gap waveguide (RGW) technology for operation in the X- and Ku-band frequency range (8–18 GHz). This paper describes the theoretical foundation and design process of the RGW power divider, followed by the development of the overall divider in two configurations: waveguide-fed and coaxial fed. Optimisation techniques were utilised to finalise the divider for fabrication and testing. Challenges in designing waveguide transitions using multiple structural configurations are discussed. The final divider was tested and validated with measurement. Results indicate that S₁₁, S₂₂ and S₃₃ are below −10 dB, output port isolation (S₂₃ and S₃₂) is below −15 dB and transmission coefficients (S₂₁ and S₃₁) are approximately −3.5 dB. In the final simulation process, the optimal values of the isolation resistors were determined based on both software-based and theoretical methods. Moreover, by evaluating the maximum electric field in the RGW structure, a higher estimated average power-handling capability was obtained compared with other technologies.

In this paper, an active quasi-circulator (QC) exhibiting a low noise figure (NF) of 1.1 dB is presented, which is composed of two couplers, three connecting transmission lines (TLs) and a nonreciprocal stage. High isolation between transmitter (Tx) and receiver (Rx) ports can be obtained through two-path signal cancelation by precisely designing the amplitude and phase of the nonreciprocal stage, which is realised by an amplifier. To reduce the additional noise introduced by the amplifier, a noise suppression technique that exploits the inherent isolation of the coupler is employed. A QC is designed to validate our design approach, which achieves an operating bandwidth of 1.82–1.96 GHz with > 20-dB Tx–Rx isolation, a minimum in-band Tx-antenna (Ant) IL of 2.6 dB, an Ant-Rx IL of 0.9 dB and a NF of 1.1 dB.

This paper proposes a filtering antenna utilising single-layer substrate-integrated waveguide (SIW) dual-mode cavities for 5G millimetre-wave user equipment. The first dual-mode cavity operates in TE₁₁₀ and TE₂₁₀ modes, generating a radiation null (RN) above the passband through cross-coupling, whereas the two hybrid modes of the other dual-mode cavity, excited together through a long slot, introduce another RN below the passband. The positions of two RNs can be independently controlled without an extra filtering circuit. The proposed single-layer fourth-order filtering antenna, designed with a centre frequency of 24.7 GHz, an impedance bandwidth of 5.67% and a maximum gain of 6.63 dBi, is well suited for 5G millimetre-wave systems. The measured results show a high degree of consistency with the simulated results.

In this article, multiple circularly polarised (CP) stacked patch antenna designs are proposed with different perturbation techniques that can be used in future CubeSat missions using NASA Near Earth Network (NEN) or Deep Space Network (DSN) ground stations. The stacked patches with different perturbations aim to optimise the axial ratio bandwidth of the antennas to cover both uplink and downlink frequency bands of NASA NEN/DSN. Combining the axial ratio bandwidth of the two stacked patches, proposed antennas can be made wideband or dual-band to replace multiple antenna systems for uplink and downlink communications. Proposed CP antennas provide the solution to overcome some of the major design challenges, such as antenna placement, limited space for solar cells and mass/volume constraints of CubeSats. The proposed antennas achieve axial ratio (AR) 3 dB bandwidths of 1.2–1.33 GHz (16%–17%) covering the X band uplink and downlink frequencies of NASA NEN. A dual-band antenna covering the uplink and downlink of NASA DSN is also achieved using the stacked patch antenna design. Alongside a wide axial ratio bandwidth, the antennas also offer a wide axial ratio beamwidth (maximum achieved $��140�°�$) and high RHCP gain (maximum 8.05 dBic gain achieved) RHCP gain. Results of the proposed designs were validated through prototype fabrication and measurements.

This study investigates the application of microwave-assisted drilling systems as an alternative to conventional mechanical drilling for marble processing. By utilising microwave energy at a frequency of 2.45 GHz, this research demonstrates how microwave radiation can effectively soften marble surfaces, reduce required drilling force, and improve surface quality. Two specialised microwave probes, Reflector Microwave Drilling Design (R-MDD) and Microwave Drilling Design-Empty Center (MDD-EC), were designed and tested to optimise the energy transfer and thermal impact on different marble types, specifically Burdur Beige and Keciborlu Angel White. Through a combination of simulation (CST Studio Suite) and experimental analysis, electric field intensity, temperature distribution, and drilling depth have been evaluated. Results indicate that microwave-assisted drilling significantly decreases burr formation and enhances drilling efficiency by generating focused thermal zones within the marble. Additionally, the MDD-EC probe's hollow conductor design allows integration with supplementary devices such as vacuum motors to manage waste discharge during drilling. This work concludes that microwave-assisted systems offer a promising cost-effective solution for hard dielectric materials in the marble industry, with potential applications extending to other high-melting-point materials.