Iet Microwaves Antennas & Propagation最新文献

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.

A novel design method of dual-band single-layer substrate-integrated waveguide (SIW) filtering antennas with independently controllable bands is proposed in this paper. The basic two-pole dual-band filtering antenna is proposed by a dual-mode rectangular SIW cavity coupled to two single-mode SIW cavities with respective radiating slots. Single cavity multi-mode is realised by etching dumbbell-shaped slots and metallised vias to achieve the purpose of broadening bandwidth and miniaturisation. The dual-mode SIW cavity acting as a common structure is fed by a coaxial feeder. The two orthogonal modes are coupled to two single-mode cavities by coupling windows to produce two two-pole passband filtering responses, respectively. Metallised vias in radiating SIW cavities are employed to realise good impedance matchings in radiating pass-bands. The two filtering radiation bands can be controlled independently, which is analysed in detail. Based on the basic two-pole dual-band filtering antenna, three- and four-pole dual-band filtering antennas are further proposed and analysed. For demonstration, two-, three- and four-pole dual-band filtering antennas with two centre frequencies of 10 and 11.7 GHz are designed, fabricated, and measured. The good agreement between the simulated and measured results verifies the proposed design methodology of single-layer SIW dual-band filtering antennas.

The Airborne Warning and Control System (AWACS) are pivotal assets in aerial operations, necessitating specialised protection measures, and serving as prime targets for enemy anti-radiation missiles (ARMs). This paper explores approaches to enhance the battlefield survivability of frequency diverse array AWACS (FDA-AWACS) by incorporating airborne radar technology onto the platform. The study commences by analysing the typical operational methods of anti-radiation missiles. Following this, a deception model is formulated for the frequency diverse array (FDA) against the passive radar homing head of anti-radiation missiles utilising the adjacent antenna single-pulse amplitude-comparison direction-finding technique. Expanding on this groundwork, the research further assesses the deceptive impacts of FDA-AWACS on direction finding cross-location techniques. Simulation results validate that FDA-AWACS can effectively counter the threat of anti-radiation missiles by diminishing their direction-finding and positioning systems.

This paper introduces a conformal frequency selective surface (FSS) with dual passbands from 9 to 9.3 GHz and 13.1–13.7 GHz, as well as one stopband from 10.4 to 10.9 GHz. The frequency response of the curved FSS coincides with the performance of the planar FSS with the same unit cell under normal incidence. The unit cell comprises two compact flower-shaped metallic slots patched on the dielectric substrate. This design has excellent stability of the incident angle up to 70°. The equivalent circuit model considering the mutual coupling between the two slots is illustrated to analyse the resonance mechanism. The whole antenna system enclosed by the conformal FSS is simulated to evaluate the loss in the far-field beam's directivity and aberration. The impact caused by the different curvatures is investigated. The samples in planar and elliptic cylindrical surfaces are fabricated. The insertion losses of both polarisations are less than 1.5 dB, as the angle of incidence varies to 60°. The frequency response of curved FSS is identical to the planar FSS under normal incidence. The maximum attenuations of both polarisations in the passbands are less than 1.38 dB, and the average transmission coefficient in the stopband is −22 dB. The conformal FSS brings slight aberration in the half power beamwidth (HPBW) of the incident beam in the passbands. Furthermore, it suppresses the main beam in the stopband by at least 25 dB.

Semi-analytical design approach to electrically small, dual-mode resonant, wideband circularly polarised (CP) microstrip annular sector patch antenna (MASPA) with variable polarization is proposed for satellite-assisted Internet-of-vehicle (IoV). At first, the upper bound of electrically small patch is theoretically laid down by advancing an interpolated algorithm to the eigen-roots of the characteristic equation, so that the radius of patch can be rapidly determined in the initial design step. In this way, MASPA with electrically small patch, multimode resonant, and frequency scannable CP angle can be yielded. Dual-mode resonant MASPAs with flare angles of 330° on air substrate, and 270° on suspended microstrip air/F4B substrates having a profile less than 0.05-wavelength are then numerically studied and experimentally validated. In the suspended microstrip case, MASPA with maximum patch radius of 0.159-wavelength (electrically small), equal impedance and tilted CP bandwidths up to 26.6%, and tilted CP angle of θ_t = −10°–35°, has been successfully implemented. Therefore, the proposed approach should be highly effective for low-profile, electrically small, wideband CP antenna designs.