Compact W-Band Silicon-Micromachined Filters with Increased Fabrication Robustness

In this paper, we present a new, robust fabrication and assembly method which allows for achieving highly-accurate responses of multilayer silicon-micromachined filters containing large-sized cavities. To obtain coupled-resonator filters with accurate and predictable frequency responses, chips fabricated with two different techniques are combined: (1) the first technique allows for fabricating geometries with accurate dimensions and well-controlled side walls, and these chips determine the electrical functionality; (2) the other fabrication technique allowing for complex 3-D geometries, including waveguide roofs, does not have the same geometrical confidence, but these chips don’t dominate the electrical performance. A 5th-order all-pole bandpass filter with fractional bandwidth of 1.3% at 76.5 GHz is designed using rectangular TE101 cavities and fabricated by silicon micromachining with gold metallization. The measured average insertion loss in the passband of the filter is 3.1 dB. The experimentally extracted unloaded quality-factor is 850. The measured insertion loss shows excellent agreement with the simulation results, while the return loss is slightly detuned.