Thin film microwave acoustic filters on GaAs

The authors report on progress made in ultraminiature resonators and bandpass filters fabricated on GaAs substrates stimulated by significant advances made in the research and development of thin-film resonator (TFR) technology on Si and other substrates and a growing need for high-performance integrated passive frequency control elements on GaAs MMICs (monolithic microwave integrated circuits). It is shown that significant size reductions and performance characteristics can be obtained by using microwave acoustic waves whose wavelength and, hence physical device size, is approximately 100000 times smaller than that of electromagnetic counterparts. Monolithic multisection SCF (stacked crystal filter) devices, exhibiting higher selectivity, have been achieved on GaAs by cascading single SCF sections, without interstage coupling elements, and have demonstrated center frequencies above 1 GHz.<>