Design of Evanescent Quad-Ridge Antenna With Compact Transition for 5G Millimeter-Wave Phased-Array Applications

An evanescent quad-ridge antenna (EQA) fed by a compact transition is proposed in this letter for 5G millimeter-wave (mm-wave) phased-array applications. The EQA is realized by an evanescent-mode quad-ridged square waveguide (QRSW) filter with a cross-shaped slot as the radiator. The compact transition is designed by leveraging the coupling between circuits on a multilayer printed circuit board (PCB) and metal ridges in the QRSW. Thanks to the proposed microstrip-to-QRSW transition, the EQA can be easily installed on a multilayer PCB and fed by active circuits. The proposed antenna is fabricated and measured. Measurement results show that the antenna can cover the 5G n257 band from 26.5 to 29.5 GHz. For beamforming demonstration, a 4 × 4 EQA array driven by mm-wave active beamformer ICs is designed and measured. The proposed EQA achieves compact size, filtering function, and easy integration with active circuits, which makes it suitable for 5G mm-wave phased-array applications.