Design and fabrication of two-pole monolithic bulk acoustic filters

A new class of miniature monolithic filters has been fabricated in the 1-GHz to 1.5-GHz range. The devices are two-pole ladder filters which incorporate two inductors, a coupling capacitor, and two bulk acoustic resonators. They are characterized by small size and weight, low insertion loss (typically between 1 and 1.5 dB), narrow passbands (between 2 and 5%), and potentially very low cost. Filters have been fabricated on both high-resistivity silicon and semiinsulating gallium arsenide substrates. Fabrication is completely compatible with all monolithic microwave IC components, and thus integrating these devices with active components on the same wafer is a straightforward procedure.<>