Iet Microwaves Antennas & Propagation最新文献

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.

This paper demonstrates a method to control the resonant transmission due to Fabry–Perot and Fano resonances through a dielectric-loaded slot in a thick conducting diaphragm embedded in a rectangular waveguide. It is shown that the location of these resonances can be controlled by introducing a gap of a different dielectric constant in the middle of the slot. The two kinds of resonances are adjusted to overlap, forming a complex behaviour with potential applications as a bandpass filter with a relatively narrow notch in the passband response. The theoretical projections are confirmed through both full-wave numerical simulations and experimental measurements. A new fabrication approach was used to overcome the shortcomings in construction that caused some discrepancies with the theory in a previous study.

Energy efficiency is fundamentally concerned in 5G/6G communication systems. Window glass considers mainly thermal energy efficiency, and it does not consider microwave efficiency too much for wireless communications, particularly in the fixed wireless access scenario, where the window glass is the only non-destructive microwave wireless propagation path between the transmitter outside the house and the signal receiver inside. Regular window glasses induce severe reflections and large penetration loss, resulting in low energy efficiency for 5G/6G communications. This paper provides a new paradigm to obtain the wave efficient window glass with designing the passive and transparent metasurface. Thanks to the glass-metasurface adjoint model and the ABCD-field adjoint analysis, it is not only appropriate for known glasses with detailed dimensions, materials etc, but also compatible with unknown pre-existing glasses such as an encrypted glass model. Moreover, the metasurface design is quite applicable for pre-existing glasses with surface mounting process, rather than the regular integrated manufacturing process in which new glasses and metasurfaces are designed and manufactured together. Spectral transmission enhancement induced by the proposed metasurface is measured, validating the effectiveness of the proposed method. In addition, surface mount process and the CPE (Customer Premises Equipment) location are discussed for a limited space. Due to the passive, and low carbon design of the metasurface, the wave efficient glass can be easily obtained, and is compatible with the CPE (Customer Premises Equipment) or RIS (Reconfigurable Intelligent Surface) for 5G/6G communications.

A novel design of quad-band power divider (PD) is proposed in this brief. By introducing the stepped impedance coupled lines, the frequency offset and power loss caused by dispersion are effectively reduced. This brief gives the complete theoretical derivation and design flow of the proposed quad-band PD, according to which people can design the PD operating in four bands. Finally, according to the design method, a quad-band PD operating at 0.7, 2.4, 3.6 and 5.3 GHz is simulated and designed. After processing and measurement, it exhibits low return loss and high isolation in the four operating bandwidths, and the simulation results are highly consistent with the experimental results, which proves the correctness of the proposed design method.

The diffraction by a finite parallel-plate waveguide cavity with perfect electric conductor loading is rigorously analysed for the E-polarised case using the Wiener–Hopf technique. By taking the Fourier transform to the unknown scattered field and applying boundary conditions in the transformed domain, the problem is formulated in terms of the simultaneous Wiener–Hopf equations. These equations are solved using the factorisation and decomposition procedure. The solution is exact but formal because it involves branch-cut integrals with unknown integrands and an infinite number of unknowns. Approximation procedures based on rigorous asymptotic are also presented, leading to an approximate solution of the Wiener–Hopf equations. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and using the saddle point method of integration. Numerical computations of the radar cross-section have been performed for different physical parameters, providing a detailed analysis of the scattering characteristics.

Inhomogeneities in the troposphere cause refraction and re-radiation of radio waves, leading to troposcatter propagation. However, traditional two-dimensional troposcatter models focus solely on the vertical scattering effects, limiting their accuracy in predicting radio wave propagation in complex three-dimensional environments. To address this limitation, a new three-dimensional troposcatter parabolic equation (3DTSPE) model is proposed. This model provides a comprehensive analysis of the three-dimensional scatterers in both vertical and horizontal dimensions and examines the impact of different scatterer structures on radio wave propagation. It selects an appropriate three-dimensional scatterer structure while maintaining computational accuracy. Simulations comparing it to the two-dimensional troposcatter parabolic equation (2DTSPE) model, the AREPS system, and the ITU-R P.617 standard, alongside real-world analysis using ERA5 atmospheric data, confirm the model's accuracy and effectiveness. This provides a solid foundation for further research on radio wave propagation in complex three-dimensional troposcatter environments.

A novel lightweight L-band combined aperture-coupled microstrip antenna has been proposed for synthetic aperture radar (SAR) applications. The proposed antenna element is composed of only two membranes. This design innovatively integrates the coupling aperture with the radiating patch, significantly reducing the number of required dielectric layers to achieve a simplified and lightweight structure. The feed line is placed on the front side to facilitate integration with the transmit/receive (T/R) module. Simulation results demonstrate that the antenna element exhibits excellent radiation pattern performance and bandwidth. A $��4�\times �4�$ passive antenna array utilising polyimide as the dielectric material was fabricated and measured to validate its performance. This array employs a 4-stage Wilkinson power divider network. Measurements show that S_1,1 is below −15 dB in the frequency range from 1.15 to 1.49 GHz, with a maximum efficiency of 72.87%. Additionally, an $��8�\times �4�$ phased array antenna was fabricated and tested. This array demonstrated stable radiation pattern performance over an azimuthal scan range of $��\pm �25�°�$ and an elevation scan of $��\pm �15�°�$. This design offers a new option for antenna modules in spaceborne SAR applications.