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.

I. Introduction

Millimeter-Wave (mm-wave) spectrums are expected to provide high data rates up to multiple Gb/s for the fifth-generation and beyond (5G/B5G) systems [1], [2]. In mm-wave bands, full-metal antenna arrays are favored for their low loss, easy fabrication, and better heat dissipation [3], [4], [5], [6], [7], [8]. Recently, full-metal antennas based on evanescent quad-ridge square waveguides (QRSWs) not only have compact aperture sizes but also can provide a good filtering function [9]. Due to the compact aperture compared to antennas based on large full-metal resonators [10], [11], [12], [13], [14] and no dielectric loss compared to antennas designed on printed-circuit-boards (PCBs) [15], [16], [17], the evanescent quad-ridge antenna (EQA) can be a good candidate for 5G mm-wave phased-array applications. However, a demonstration of the EQA in the mm-wave phased-array application is rarely found in the literature because there is by far no proper antenna interface.