Millimeter-Wave Wide-Angle Ridge Gap Waveguide Multibeam Antenna Fed by 3-D Printing Butler Matrix

A novel 3-D printing ridge gap waveguide (RGW) wide-angle endfire dual-dipole multibeam antenna operating at millimeter-wave (mmW) frequency spectrum is proposed, which consists of an RGW $6\times 6$ Butler matrix (BM) and an endfire dual-dipole antenna array. This article provides a detailed description of the working principle and design process of the $6\times 6$ BM. By incorporating RGW technology, transmission losses of the beamforming network (BFN) are effectively reduced, which enhances the radiation efficiency of the final multibeam antenna. A modified endfire dual-dipole antenna with wide beamwidth is introduced. By integrating the $6\times 6$ BM with the endfire dual-dipole antenna array, the final multibeam antenna is realized. This antenna provides a maximum scanning-plane half-power beamwidth (HPBW) coverage of ±83.5° and an associated gain varying from 12.3 to 13.8 dBi at 28 GHz. Furthermore, an analysis is conducted on the fabrication issues related to manufacture tolerance and surface roughness in 3-D printing processes, which evaluate the ability and accuracy of 3-D printing technology in mmW antenna applications.