Ying Liu

This paper proposes a circularly polarized (CP) antenna array featuring high aperture efficiency, a low in-band radar cross section (RCS), and a low profile. First, two different patch antenna elements are designed, which exhibit desirable CP performance and a 180° reflection phase difference under x-polarized normal incidence within the same operation band. These elements are then arranged in a chessboard configuration to simultaneously achieve high aperture efficiency and in-band RCS reduction under x-polarized normal incidence. Subsequently, the parasitic units are uniformly embedded into the array elements, which are employed to realize reflection phase cancellation with the array elements under y-polarization normal incidence. The simulated results show that the proposed array achieves a peak monostatic RCS reduction of 12.8 dB, and the 6 dB RCS reduction bandwidth fully covers the antenna’s operating bandwidth under both x- and y-polarized normal incidences. Moreover, the gain of the antenna array reaches 18.2 dBic at 3 GHz with an aperture efficiency of 58% and a profile of 0.03λ. A good agreement is obtained between the simulated and measured results. This design successfully combines the advantages of high aperture efficiency, dual-polarized in-band RCS reduction, and a low profile, making it highly valuable for aerospace satellite communications and unmanned aerial vehicle data links.

In this communication, a hybrid-controlled reconfigurable leaky-wave antenna (R-LWA) based on a double-layer slow-wave structure is proposed. The proposed design employs a varactor-loaded extended double-layer composite (E-DLC) unit to realize tunable slow-wave characteristics through simple interlayer biasing, while elliptical radiating patches embedded into the lower slots provide stable external radiation. Under frequency control, the proposed R-LWA maintains 180° full-space beam scanning across the different reverse-bias conditions, covering an overall operating frequency range of 5.03–6.85 GHz with a scanning rate ranging from 6.7°/% to 7.5°/%. More importantly, under voltage control, the antenna further enables fixed-frequency beam scanning within the effective operating frequency range. Experimental results demonstrate that the maximum beam reconfiguration range can also reach 180°, thereby providing an additional beam-control dimension without sacrificing the original frequency-scanning capability. By combining frequency-controlled full-space beam scanning and voltage-controlled wide-angle beam steering within a unified slow-wave platform, the proposed design offers enhanced beam-control flexibility and angular coverage for multifunctional integrated systems.

A left-handed circularly polarized (LHCP) and frequency reconfigurable Fabry-Pérot cavity antenna (FPCA) is proposed using mechanically reconfigurable Fabry-Pérot cavity (FPC). By using chiral metasurfaces as the top and bottom boundaries of the FPC, LHCP waves can be multiply reflected within the cavity while preserving the same handedness. Moreover, the resonant frequency is directly dependent on its twist angle. Hence, the antenna can realize frequency reconfiguration by rotating the chiral partially reflective surface (PRS). The chiral bottom reflector is designed with low polarization loss. Additionally, a chiral PRS is designed to achieve both chiral reflection and polarization-stable transmission during the rotation of the PRS, ensuring stable LHCP radiation during reconfiguration. Finally, a Fabry-Pérot cavity antenna is obtained under the excitation of an LHCP source antenna. It achieves narrowband performance in terms of gain and axial ratio bandwidth with a high directionality. Moreover, a wide and continuous frequency reconfiguration range of peak gain is realized from 5 to 6.02 GHz. The maximum peak gain of 19.98 dBic with a variation of less than 1.9 dB is realized. Maximum aperture efficiency reaches 55.55%. A prototype has been fabricated and measured for verification. Both simulation and measurement results show good agreement, confirming the feasibility of the proposed design method.

In this letter, a circularly polarized (CP) filtering grid-slotted patch antenna (GSPA) is proposed for millimeter wave (MMW) applications. The antenna mainly consists of a corner-truncated patch radiator, a coupling slot, and a substrate integrated gap waveguide (SIGW) feeding network. By properly incorporating several parasitic structures, the proposed design achieves wide axial-ratio bandwidth (ARBW) and good stopband suppression. Specifically, a cross strip and four parasitic strips are introduced to broaden the ARBW, while the radiator, coupling slot, and feeding network together form a third-order filter for upper stopband suppression. In addition, a circular ring and two folded strips are incorporated to generate two radiation nulls in the lower stopband. Since the added parasitic structures occupy no additional space, the antenna remains compact with an aperture of only 0.37λ0 × 0.37λ0. For validation, a 1 × 4 filtering antenna array is fabricated. Measurements show a −10 dB impedance bandwidth (IBW) of 23.3% and a 3 dB ARBW of 27.8%, fully covering the 5G MMW band (24.25–29.5 GHz). Meanwhile, the out-of-band suppression is greater than 22 dB.