300-GHz microstrip-to-waveguide transition integrated in LTCC

A 300-GHz probe-type microstrip-to-waveguide transition in low-temperature co-fired ceramic (LTCC) is presented. A via fence and air holes are used to form a three-dimensional impedance-matching structure and a vertical hollow waveguide inside the multi-layer LTCC substrate. By incorporating the air-hole matching structure beside the microstrip probe, the bandwidth is enhanced. A prototype of the LTCC probe-type transition exhibits minimum insertion loss of 1.2 dB and 36-GHz bandwidth with less than 10-dB return loss. The compact transition makes it easy to integrate it in a low-cost LTCC package with an MMIC chip.