A Millimeter-Wave “Quasi-Reflectionless” Filter Prototype Implemented with Micromachined Silicon

A proof-of-concept “quasi-reflectionless” filter integrated on a micromachined silicon-on-insulator (SOI) substrate platform is described. The filter is designed to have a low-pass response with 3 dB roll-off at 150 GHz. Suspended high-impedance transmission lines are incorporated as inductive elements, in addition to thin-film resistors, and metal-insulator-metal capacitors to realize the complete filter architecture. Through-silicon vias provide access to the circuit ground plane. Measurements of the filter are conducted using a broadband on-wafer measurement setup with dual-band probes covering the dc-to-220 GHz frequency band. The filter exhibits a return loss greater than 15 dB over the measured frequency range and to the authors’ knowledge is the first reflectionless filter prototype operating over 100 GHz and implemented on micromachined SOI.