Planar microwave and millimeter-wave lumped elements and coupled-line filters using micro-machining techniques

Planar microwave and millimeter-wave inductors and capacitors have been fabricated on high-resistivity silicon substrates using micro-machining techniques. The inductors and capacitors are suspended on a thin dielectric membrane to reduce the parasitic capacitance to ground. The resonant frequencies of a 1.2 nH and a 1.7-nH inductor have been increased from 22 GHz and 17 GHz to around 70 GHz and 50 GHz, respectively. We also report on the design and measurement of a new class of stripline filters suspended on a thin dielectric membrane. Interdigitated filters with 43% and 5% bandwidth have been fabricated and exhibit a port-to-port 0.7 dB and 2.0 dB loss, respectively, at 14-15 GHz. The micro-machining fabrication technique can be used with silicon and GaAs substrates in microstrip or coplanar-waveguide configurations to result in planar low-loss lumped elements and filters suitable for monolithic integration or surface mount devices up to 100 GHz