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

SUMMARY We attempt to design and fabricate of a 4 × 4 Butler matrix forshort-millimeter-wavefrequenciesbyusingthemicrofabricationprocessforapolytetraﬂuoroethylene(PTFE)substrate-integratedwaveguide(SIW)bythesynchrotronradiation(SR)directetchingofPTFEandtheadditionofametalﬁlmbysputterdeposition.First,thedimensionsofthePTFESIWusingrectangularthrough-holesforG-band(140-220GHz)operationaredetermined,andacruciform90 ◦ hybrid coupler and an intersection 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.