Design and Fabrication of PTFE Substrate-Integrated Waveguide Butler Matrix for Short Millimeter Waves

Abstract

SUMMARY We attempt to design and fabricate of a 4 × 4 Butler matrix for short-millimeter-wave frequencies by using the microfabrication process for a polytetrafluoroethylene (PTFE) substrate-integrated waveguide (SIW) by the synchrotron radiation (SR) direct etching of PTFE and the addition of a metal film by sputter deposition. First, the dimensions of the PTFE SIW using rectangular through-holes for G-band (140-220 GHz) operation are determined, and a cruciform 90 ◦ hybrid coupler and an inter-section circuit are connected by the PTFE SIW to design the Butler matrix. Then, a trial fabrication is performed. Finally, the validity of the design result and the fabrication process is verified by measuring the radiation pattern. key words: microstructure, X-ray lithography, dielectric loaded waveguides