Iet Microwaves Antennas & Propagation最新文献

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.

This paper demonstrates a miniaturised frequency selective rasorber (FSR) that incorporates meander cross-rings to realise a wide transmission band. The FSR comprises a resistive layer and a bandpass frequency selective surface (FSS), which are separated by an air layer. The resistive layer is constructed by employing meander cross-rings equipped with lumped resistances, where the inner arms of cross-rings are bent to obtain a parallel resonant circuit with large inductances and small capacitances to achieve broadband transmission at high frequencies. The bandpass FSS is implemented using a triple-layer metallic structure, where two identical square ring layers are coupled through a central metal grid layer to form the transmission band. The measured results indicate that the absorption band with absorptance exceeding 90% is from 3.5 to 9.4 GHz, and the passband exhibiting insertion loss of less than 1 dB spans from 11.92 to 17.98 GHz with a 40.5% relative bandwidth, which matches well with simulated ones. This FSR has the characteristics of simple structure and high performance, which provides a novel concept of stealth applications.

In this paper, an electronically 1-bit reconfigurable reflectarray antenna (RRA) with wide-angle beam-scanning and high efficiency performance is presented for formation satellite communication applications. A 1-bit phase distribution can be generated by controlling the state of the PIN dipole in the configurable element comprising a double split ring (DSR) patch and two T-shaped parasitic structures. The resonant frequency of the DSR patch in both states can be optimised by a T-shaped parasitic structure, which is beneficial to improving the bandwidth and aperture efficiency. A 180° ± 20° phase difference can be realised from 9.7 to 10.3 GHz only by controlling one PIN dipole loaded on the proposed element, which ensures stable radiation performance over a larger band. To validate the effectiveness of the proposed element, a prototype RRA containing 20 × 20 units is designed and measured. A ±60° beam scanning range with the gain drop of 3.2 and 3.3 dB in the xoz and yoz planes is realised, which verifies the wide-angle beam-scanning ability of the RRA. The measured peak gain is 25 dBi at 10 GHz in the broadside direction, corresponding to an aperture efficiency of 25.2%. Meanwhile, the 1-dB gain bandwidth of the proposed RRA is 12.6%.