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 similar to 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.