LTCC-Based Substrate Integrated Image Guide and Its Transition to Conductor-Backed Coplanar Waveguide

A substrate integrated image guide (SIIG) transmission line based on the low temperature co-fired ceramic (LTCC) technology is proposed in this letter. Compared with other existed SIIGs, this configuration is easier to design and offers better fabrication reliability. Then, a compact transition between a SIIG and a conductor-backed coplanar waveguide (CPW) is designed and fabricated. Within the frequency range of 56.5 ~ 67.5 GHz, the measured return loss is better than 10.8 dB while the maximal insertion loss is 3.4 dB including a back-to-back CPW-SIIG transition and a 30 mm length SIIG. Therefore, the measured insertion loss for such a transition from the CPW to the SIIG is evaluated to 0.748 dB at the center frequency of 62 GHz.