Iet Microwaves Antennas & Propagation最新文献

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.

A method of batch generation of frequency selective surface structure is proposed in this paper. The method of random image generation and random diode insertion position is used to generate a database through a large number of automatic calculations to replace manual design by screening high-performance cells. This method can achieve most of the possible indicators of FSS, significantly reduce the manual workload and shorten the design cycle.

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.