SBAR filter monolithically integrated with HBT amplifier

Abstract
The authors describe the successful monolithic integration of bulk acoustic filters with gallium arsenide integrated circuits. Data are presented for a filter-amplifier chip with a center frequency of 1023 MHz, a 4 MHz bandwidth, and +14 dB gain. The size of the filter-amplifier chip is 1.6*3.2 mm. The monolithic filter is an SBAR (semiconductor bulk acoustic resonator) stacked crystal filter. The filter was fabricated with sputtered aluminum nitride piezoelectric films. The active circuit is a gallium arsenide HBT amplifier. The amplifier is a two-stage design and has biasing resistors and coupling capacitors on-chip. The integration process for the monolithic SBAR-HBT filter-amplifier is outlined.

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