A mm-Wave Low-Loss Transition from Microstrip Line to Air-Filled Substrate Integrated Wavguide on Printed Circuit Board Technology

This paper introduces the design of an air-filled substrate integrated waveguide (AFSIW), and a transition design from microstrip line (ML) to AFSIW at 60 GHz. The proposed structure is realized by printed circuit board (PCB) technology so that the fabrication cost is low and the whole structure is easy to be integrated with other planar components. An equivalent circuit model of the proposed ML-AFSIW transition is proposed and verified by full-wave simulation. To verify the proposed idea, a back-to-back transition is designed, fabricated and measured. The measured return loss is higher than 15 dB from 60.6 to 64.5 GHz. The minimum of measured insertion loss is 0.2 dB at 61 GHz. The measured results show that the proposed ML-AFSIW transition is suitable for millimeter-wave (mm-Wave) application.