Iet Microwaves Antennas & Propagation最新文献

In this work, a simple analytical model based on the array factor to effect 1-bit electronic reconfigurability in one-dimensional 1-D leaky-wave antennas (LWAs) is proposed. The model, based on the array factor, outlines the discrete control of the phase constant along the longitudinal direction of the LWA $��\left({\beta }_z\right)�$ subsequently describing the beam scanning logic in the H-plane. The effectiveness of the proposed approach is evaluated by comparison against full-wave calculations. An extremely low-profile electronically reconfigurable 21-element LWA operating at X-band is then fabricated and measured to validate the proposed concept. The individual antenna element making up the array is designed at X-band and is capable of switching between radiating and non-radiating states by use of a PIN diode used to control the resonant frequency of the element. The limitations of both the proposed approach and the antenna are also evaluated.

This study proposes a novel three-dimensional integral-equation-based electromagnetic solver with surface susceptibilities of metasurfaces that satisfy the generalised sheet transition conditions (GSTCs). The metasurface is replaced by an equivalent zero-thickness sheet with surface susceptibilities, which can be extracted using the retrieval method deduced from the GSTCs. We consider the problems of composite structures with metasurfaces for greater generality and applicability. The integral equations of the problems are formulated and discretised using Rao–Wilton–Glisson (RWG) basis functions through Galerkin's testing procedure. We also propose a technique for enforcing the boundary condition at the interface, which should be carefully considered within the problem formulation of composite structures. The proposed method is validated by using a circuit-analog-based absorber to extract the surface susceptibilities. Composite structures, including flat and curved metasurfaces, are employed to verify the IE-GSTC solver, and numerical simulation results are compared with those obtained from a commercial finite-element method-based simulation (FEM-HFSS).

Self-interference (SI) suppression has always been critical for simultaneous transmit and receive (STAR) systems. To address the strong coupling between nearby transmit and receive antennas, this study employs an improved quantum genetic algorithm (IQGA) to eliminate SI by combining digital self-interference cancellation (SIC) and adaptive beamforming (ABF). Through digital SIC, both transmit noise and transmit signals are suppressed. The objective of the transceiver beamformer is to further reduce SI through SIC while simultaneously achieving high transceiver gain in the desired direction. IQGA represents the weights of feasible transceiver beams using chromosomes. By updating the population through quantum rotation, quantum crossover and quantum mutation strategies, IQGA demonstrates improvements in convergence accuracy, convergence speed, and reliability. In comparison to traditional ABF approaches, IQGA eliminates the need for complex matrix calculations and numerical derivations, thereby simplifying the solution process. The simulation results indicate that by cancelling the SI component through SIC and ABF, an isolation of 159.78 dB can be achieved at a transmit power of 1000 W. This represents an improvement of 40.32 dB compared to SIC alone and 113.87 dB compared to scenarios without SIC and ABF.

Over-the-air (OTA) tests have become an essential tool to assess the performance of a wireless device under controllable and repeatable conditions. Such benefits provide a deep insight into the device under test (DUT) performance; nevertheless, the realism achieved by OTA tests is still moderate in comparison to open-field tests. This contribution takes the OTA testing method for wireless devices and combines it with the wave field synthesis (WFS) technique to increase the efficiency, reliability and especially the realism of the tests. The main focus of this contribution is to use the aforementioned method to emulate realistic GNSS scenarios inside an anechoic chamber, where multiple virtual satellite signals are electronically generated in the far field along with their individual trajectories. For the validation and verification of the method, a commercial GNSS antenna and receiver are placed as the DUT inside the chamber. The WFS calibration methods implemented in an OTA testbed are described in detail along with the performance analysis obtained by each method. This study strives to establish the foundation for a forthcoming standardisation of the proposed methodology, applicable not only to GNSS devices but also to any variety of wireless devices.

The design of artificial electromagnetic materials (AEMMs) depends highly on full-wave numerical simulations or equivalent circuit model (ECM)-assisted analysis. This work proposes an intelligent design method using a deep learning (DL) technique based on the residual neural network (ResNet) to improve its efficiency. Firstly, adopting pixeled matrix modelling methods enhances the freedom of design. Next, the staircase approximation is utilised for the S-parameter curve, which also describes the required electromagnetic (EM) property to be used in the training process. These processed samples, along with their corresponding labels, are transformed and fed into ResNet for training. After these procedures, the structural matrix of the desired curve can be predicted through well-trained networks. To validate the effectiveness of the method, typical notched-band frequency selective absorbers (FSAs) are designed, while the reflective band can easily be adjusted. Compared with conventional methods and other deep neural network (DNN)-based methods, this method performs more efficiently and accurately. Finally, an illustrative sample is fabricated to validate the prediction result.

This paper presents a 4 $��\times �$ 4 millimeter-wave (mm-wave) phased array antenna operating in the Ka-band (27–34 GHz) fabricated using low-temperature co-fired ceramic (LTCC) technology. The proposed array employs several innovative design features to achieve superior performance. An oversized aperture, combined with a parasitic patch and an embedded air cavity, significantly enhances the gain and bandwidth. Additionally, an asymmetric stripline feed structure minimises back radiation and facilitates multi-layer integration, enabling seamless compatibility with beamforming systems. The antenna demonstrates a measured impedance bandwidth of 27% and a realised gain of 17.5 dBi at 29 GHz, with a scanning angle of $��\pm �25�°�$. These results establish the design as a compact, high-efficiency, and broadband solution for mm-wave phased array applications in 5G and beyond. Experimental validation using a 16-channel beamformer module further highlights the practicality of the design for real-world deployment.

Dual-band antennas have found extensive applications in the fields of communications, guidance, tracking systems, etc. However, traditional designs often struggle to simultaneously achieve high gain, wide impedance bandwidth and conical beam characteristics. In response to this challenge, a dual-band high-gain conical beam antenna with broad impedance bandwidth based on a nested horn operating at Ku-/Ka-band is presented in this paper. The nested horn excited by metal probes comprises a Ka-band circular waveguide horn and an outer nested Ku-band waveguide horn. The proposed antenna operates in the TM₀₁ mode, demonstrating rotationally symmetrical field distribution, which enables the generation of conical beams. The utilisation of a ridge waveguide further widens the impedance bandwidth. The incorporation of dual reflectors enhances the directivity of electromagnetic wave propagation, leading to increased gain and a fixed beam pointing angle. The measured results show that the proposed antenna operates at 12.8–18 GHz in the Ku-band and 25.2–43.5 GHz in the Ka-band, with relative impedance bandwidths of approximately 33.8% and 53.3%, respectively, covering nearly the entire Ku-band and Ka-band. The peak gain reaches 12.2 dBi at 15 GHz and 16.4 dBi at 40 GHz. Furthermore, the maximum beam pointing angles are maintained at 30° for both frequency bands.

This paper significantly improves the previously proposed novel multiband waveguide filter implementation employing cylindrical resonators. The improved model has the advantages of a further reduced footprint using stacking shunt resonators horizontally and vertically and the ability to realise advanced filtering functions, including transmission zeros below and above the passbands. The coupling matrix synthesis with a brief example and a detailed filter design with considerations for additional coupling and in-line and folded topologies is given. Several filter prototypes, namely third-order quad-band and quintuple-band in-line filters and a sixth-order dual-band folded filter in Ku-band, were designed to validate the proposed model. Selective laser melting (SLM), a metal 3-D printing technique where metal powder is selectively melted with a laser layer by layer, was used to fabricate a dual-band folded filter prototype in copper to validate the proposed model since the model has a complex inner geometry. Additionally, selective laser melting has the advantage of monolithic near-net shape fabrication, eliminating assembly, improving reliability, and reducing weight. The measured results show good agreement with the simulations.

This paper presents a novel dual-band waveguide-fed circularly polarised (CP) horn antenna for the feeder of synthetic aperture radar (SAR) onboard microsatellite. The proposed horn antenna consists of an asymmetric linearly tapered slot and a waveguide feed. The C-/X-band left-hand circular polarisation (LHCP) design was simulated, and the 3D-printed prototype was fabricated to validate the simulation and measured in an anechoic chamber. The measured circularly polarised (CP) antenna can achieve dual-band operations with a 3 dB axial ratio bandwidth of 40% (5–6.5 GHz; 8.5–10 GHz), VSWR less than 1.4 in the operating band and a peak gain of 13.6 dBic (5.3 GHz) and 18.5 dBic (9.4 GHz). The measured half-power beamwidth (HPBW) at C-band and X-band frequencies in the xz-plane and yz-plane are achieved at 26°/37° and 18°/23°, respectively. The proposed antenna offers several advantages over current CP antenna designs, including simpler design, low-cost manufacturing, better impedance matching, wider AR bandwidth and lower sidelobe levels.

An LC quadrature voltage-controlled oscillator (LC-QVCO) with novel compensated coupling networks to achieve both low supply sensitivity and quadrature phase enhancement is proposed. Designed and fabricated in a standard 0.18-μm CMOS process, the proposed QVCO improves the supply noise rejection by more than 16.72 dB compared with the conventional LC-QVCO and achieves quadrature phase error of < 0.86° within the frequency tuning range from 3.32 to 3.52 GHz, whereas occupying a core area of 504 × 400 μm² and consuming 3.2 mA including the bias circuitry, from a 1.8-V supply voltage. The phase noise is measured to be −110.64 dBc/Hz at 1 MHz offset and −130.49 dBc/Hz at 10 MHz offset from the high-band carrier frequency at 3.52 GHz.