A Micromachined High-Q Microstrip Line with a Broadband Microstrip-to-CPW Transistion

A high-Q micromachined microstrip line with its corresponding broadband microstrip-to-CPW transition is presented. The micromachined suspended-ground microstrip line is fabricated monolithically to eliminate the usage of multiple substrates and more complicated processes including wafer bonding and thru-substrate vias. Furthermore, via-less connections between the signal line and ground plane of the microstrip can be easily implemented. The fabricated 1-mm long suspended ground microstrip line with back-to-back transition shows an excellent RF performance with insertion loss of less than 0.36 dB and reflection below -18 dB over a broad bandwidth from dc to 30 GHz.