Cross-sectional Lamé mode filters for UHF wideband applications

We demonstrate the first ladder filter based on the use of the recently demonstrated cross-sectional Lamé mode resonators (CLMRs). This device shows a fractional bandwidth (BW3db) as high as 3.3% while enabling an insertion-loss as low as 2.5 dB. As the resonance frequency of CLMRs can be controlled lithographically without significantly degrading their electromechanical coupling coefficient (kt2), this novel filtering technology permits to cover multiple frequency bands without adding fabrication complexity. In particular, as demonstrated in this work, this feature enables the use of CLMFs in platforms adopting carrier-aggregation. In addition, the capability of achieving large BW3dB around lithographically defined center frequencies permits to build transmitter and receiver modules of next-generation Radio-Frequency (RF) front-ends on the same chip and without adding fabrication steps.