50O-terminated ALN MEMS filters based on lamb wave resonators

Abstract

This paper reports on an implementation of an ultra-miniature 140 MHz narrowband filter based on aluminum nitride (AlN) Lamb wave resonators (LWRs). First, a design principle for ladder type LWR filters is presented. The fabricated device, cascaded with an inductor-capacitor network, is well matched to 50 ohm and shows a remarkably high performance. Further, the filter is monolithically integrated with a pair of on-chip capacitors and only the inductors are needed, thus involving much simpler circuits and size savings. The final filter shows a low pass-band insertion loss (IL) of 2.78 dB and steep filter skirts and occupies much smaller areas than its surface acoustic wave counterpart in the intermediate frequency band. KEYWORDSLamb wave resonator, aluminum nitride, MEMS, intermediate frequency, band-pass filter