Iet Microwaves Antennas & Propagation最新文献

A compact leaky-wave antenna (LWA) with innovative phase-shift asymmetric coupling for continuous beam scanning is presented. The antenna utilises a slow-wave half-mode substrate integrated waveguide with spoof surface plasmon polaritons (SW-HMSIW-SSPP) transmission line structure to achieve ultra-compact dimensions in both longitudinal and lateral directions. The radiation characteristic is achieved using sinusoidal modulation on the SSPP structure. To enable continuous beam scanning through broadside, a novel and simple phase-shift asymmetric coupling method is developed by placing sinusoidally modulated patches with π/2 phase shift on the metallised blind via-hole arrays. This approach effectively suppresses the open stopband (OSB) and enables continuous beam scanning from backward to forward directions without radiation degradation at broadside. A prototype of the proposed LWA is fabricated and characterised. The measured results demonstrate that the antenna with 12 unit-cells operates over a wide frequency range from 14.3 to 20.5 GHz with continuous beam scanning from −40° to +30°, while maintaining an ultra-compact aperture of only 6.67 λ₀ × 0.27 λ₀.

A gain enhancement method is presented for a circularly polarised (CP) wideband Fabry–Perot resonator antenna (FPRA). The proposed antenna structure consists of a multilayer configuration of closely spaced truncated dielectric plates (TDPs) and a broadband CP patch array. By appropriately designing the patch array, the 3-dB axial ratio (AR) bandwidth is effectively broadened, and the overall gain performance of the antenna is improved. The TDPs act as partially reflective surfaces (PRS), exciting the Fabry–Pérot (FP) resonance effect to further enhance the radiation efficiency and gain. Moreover, the multilayer TDPs are utilised to optimise the phase distribution of the antenna aperture field, significantly reducing its non-uniformity and achieving a more uniform phase profile. This leads to an extended 3-dB gain bandwidth and enhanced peak gain. Measurement results demonstrate that the proposed antenna achieves a −10 dB impedance bandwidth of 55.6% (8.73–15.45 GHz), an AR bandwidth of 42.7% (9.50–14.65 GHz) and a 3-dB gain bandwidth of 50.8% (9.52–16 GHz), with a peak gain of 15.19 dBic. An aperture efficiency of 46.3% is achieved at 10.2 GHz.

In this paper, we propose a phased antenna array with enhanced coupling configuration that integrates ultra-wideband performance, low profile and significantly reduced scattering. The antenna design leverages an innovative arrangement of cross-stacked planar dipole layers and a nonbalanced feed structure, achieving a miniaturised and highly integrated form. To further enhance performance, we incorporate resistive frequency selective surfaces (RFSS), short-circuit columns and optimised dielectric layers to mitigate multifrequency resonance points caused by the ground plane and unbalanced feeding. These innovations enable a broader 9:1 operating bandwidth. Additionally, the integration of a hybrid-functional metasurface is optimised using a synergy of equivalent circuit characterisation and space mapping (SM) technology, improving both design efficiency and functionality. We also extend the phase cancelation technique into the folded metasurface to induce reflection phase differences, resulting in an RCS reduction of more than 5 dB across the entire frequency band. An 8 × 8 antenna array was fabricated and tested, demonstrating exceptional wide bandwidth, wide scanning angles and low scattering characteristics, validating the effectiveness of the proposed design.

This work presents a rigorous analysis of H-polarised wave diffraction by a finite parallel-plate waveguide cavity with perfect electric conductor loading, employing the Wiener-Hopf technique. The unknown scattered field is transformed using the Fourier transform, and boundary conditions are enforced in the transformed domain, leading to a system of simultaneous Wiener-Hopf equations. These equations are solved through the application of factorization and decomposition procedures. The solution is exact but formal, as it involves branch-cut integrals with unknown integrands and an infinite number of unknowns. Approximation procedures based on rigorous asymptotic analysis are proposed and employed, resulting in an approximate solution to the Wiener-Hopf equations. The scattered field both inside and outside the cavity is determined by applying the inverse Fourier transform in conjunction with the saddle-point method. Numerical results for the radar cross section under varying physical conditions are provided to illustrate the scattering behaviour in the H-polarised case.

This paper presents a novel method for designing a wideband dual-polarised multibeam transmitarray antenna. First, a dual-polarised element is implemented through a polarisation-separating, orthogonal-interleaved three-dimensional frequency-selective surface (3-D FSS). Subsequently, a wideband dual-polarised unit cell is developed by integrating true-time-delay (TTD) technology, allowing full 360° linear phase shifting for distinct polarisations. A superposition method is then employed to efficiently and stably determine the phase distribution of the array, facilitating multibeam radiation. Finally, measurements of the fabricated transmitarray antenna validate its excellent quad-beam radiation performance at 5 GHz for both vertical and horizontal polarisation, with each beam exhibiting precise spatial separation and maintaining sidelobe levels below −12 dB and cross-polarisation suppression ratios better than −20 dB. The 3 dB gain bandwidths are measured to be 16.31% for vertical polarisation and 16.96% for horizontal polarisation, with corresponding peak aperture efficiencies of 37.27% and 35.63%, respectively.

In this paper, a compact broadband flexible wearable antenna with an improved high-order mode radiation pattern is designed and analysed using the characteristic mode analysis (CMA) method. Through loading nonuniform stacked patches on traditional metasurface (MS) unit cells, the radiation properties of high-order mode are enhanced, thereby widening the operating bandwidth of the antenna. The antenna achieves broadband impedance matching by simultaneously exciting the slot radiation mode and two metasurface modes via a coupling feed. The antenna is fabricated using membrane circuits on felt substrates. It is demonstrated that the antenna achieves a −10 dB bandwidth of 4.42–7.66 GHz (53.6%) and a 3 dB gain bandwidth of 4.55–7.54 GHz (49.5%). The peak gain is measured at 9.6 dBi while maintaining a compact size of 0.62 × 0.62 λ₀². In addition, the robustness and specific absorption rate (SAR) properties of the proposed antenna are evaluated.

This work introduces the biconical cavity as a high-performance resonator for multimode wideband bandpass filters. Unlike conventional cylindrical cavities, its tapered geometry enhances mode separation and extends the rejection band compared to an equal-order cylindrical cavity of the same configuration without additional tuning elements, while maintaining compact size. To verify this advantage, quadruple- and quintuple-mode bandpass filters using biconical cavities are directly compared with equivalent cylindrical implementations. Both quadruple- and quintuple-mode filters using biconical cavities are designed, fabricated and measured. The quadruple-mode filter operates at 3.82 GHz with 46.8% fractional bandwidth and three transmission zeros, whereas the quintuple-mode filter achieves 67.2% bandwidth at 3.52 GHz with four transmission zeros. Close agreement between measured and simulated results confirms improved stopband suppression and stable passband matching, establishing the biconical cavity as a compact and practical alternative for next-generation wideband communication systems.

This paper proposes a novel phased array which has outstanding advantage of broadband, miniaturisation and wide-angle scanning. First, leveraging a conventional antipodal Vivaldi structure enhanced with microstrip line side-feeding, resistive loading techniques and top-loaded radiating patches. Then, wide-angle impedance matching and stable scanning performance are realised by incorporating a dielectric matching layer above the radiating element and introducing dummy elements at the array edges. Additionally, elliptical parasitic patches are integrated to suppress gain fluctuations during beam scanning. Finally, a miniaturised 6 × 10 finite array is fabricated and measured. Both simulated and measured results indicate that the array maintains an active voltage standing wave ratio (VSWR) below 2.5 across a 4:1 bandwidth (2.1–8.4 GHz), supporting scan coverage up to ± 60° in the E-plane and ± 50° in the H-plane. The gain fluctuations at key frequencies is constrained within 3 dB throughout the scan range. Therefore, the design achieves a comprehensive property of low cost, compact size, ultra-wideband operation, wide-angle impedance matching and wide-angle scanning. This design demonstrates great potential for space-constrained applications, particularly in airborne multifunction radar systems.

An innovative deep-learning driven convolutional perfectly matched layer (CPML) integrated into the hybrid implicit-explicit finite-difference time-domain (HIE-FDTD) method is proposed to improve the efficiency of open-region electromagnetic simulations. The Autoformer neural network is introduced to replace the conventional multi-layer CPML structure. Both the computational domain size and algorithmic complexity are reduced since only a single-layer boundary layer is involved in the new model. Benefiting from the time series decomposition and sparse attention mechanism, the wave absorption efficacy of the proposed model is significantly improved without backward cumulative errors. Through a column-stacked data acquisition approach, the Autoformer-based CPML is compatible with both the FDTD and HIE-FDTD frameworks. The time step size of this proposed method is only determined by the coarse grid size, thereby extending the applicability of intelligent absorption boundaries beyond traditional FDTD limits. Numerical examples demonstrate that this method markedly improves computational efficiency while maintaining excellent wave absorption performance. Additionally, results confirm the method's robustness in complex scenarios, including multi-material, multi-source and multi-scale environments.

In this work, a graphene-based tunable phase shifter is proposed which deploys a semiautomated procedure for graphene deposition leading to a high-quality graphene transfer. The deposited graphene's complex impedance values are extracted from measured transmission coefficient values in the X band. Analysis of different widths of graphene is performed for better understanding of the microwave properties of graphene. It is evident that by decreasing the width of graphene, the impedance of graphene decreases, making it more conductive for lower widths. In order to observe the microwave tunable behaviour of graphene, varying DC biasing voltages are applied and the variation of transmission coefficients are measured. From the extracted values of complex impedance of graphene, it is observed that graphene possesses significant reactance variation, something that is not considered in literature. The reactance variation can be exploited in the variation of the phase of microwave signals. The reactance variation of graphene is further enhanced for increased phase variation by deploying it with an Interdigitated Capacitor (IDC). The IDC graphene phase shifter provides a phase variation of 60° with negligible amplitude variation at 9 GHz.