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

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.