All-Metal Filtering Antenna Array Using Slow Wave Structure and Double-Grating Waveguide

This communication proposes a novel filtering antenna design methodology that integrates a slow-wave structure with a double-grating waveguide (DGWG), forming an all-metal structure with inherent frequency-selective radiation. The proposed method achieves both radiation and passband filtering through a unified structure. The designed slow-wave structure not only radiates a wideband fixed-beam, but also intrinsically generates upper cut-off frequency. The DGWG is used to excite the slow-wave structure while simultaneously providing lower cut-off frequency. This dual mechanism enables independent tuning of the upper and lower cut-off frequencies. To validate the concept, aKa-band 1×4 antenna array prototype is designed, fabricated, and measured. The prototype achieves a wide impedance bandwidth (|S11| < -10 dB) of 27.6–37.6 GHz and a stable beam direction of around 76°. The peak gain reaches 16.5 dBi with a fluctuation below 1.5 dB across the operating band. Additionally, the out-of-band suppression levels exceed 25 dB. The total efficiency within the operating band is above 85%. Owing to its excellent selectivity, high gain, and high efficiency performance, the proposed filtering antenna array offers promising applications in millimeter-wave communication systems.