Cross-Sectional Lamé Mode Ladder Filters for UHF Wideband Applications

This letter reports on the first demonstration of ladder filters based on the recently demonstrated cross-sectional Lamé mode resonator (CLMR) technology. These filter prototypes show a fractional bandwidth (BW_3dB) as high as 3.3% and an insertion loss as low as 0.4 dB. As the resonance frequency of CLMRs can be lithographically controlled without significantly degrading their electromechanical coupling coefficient (k²_t), multiple contiguous frequency bands can be covered by this filter technology without adding fabrication complexity. This unique feature addresses one of the most crucial challenges associated with the development of miniaturized mobile platforms adopting carrier-aggregation. Furthermore, the capability of achieving large BW3dB, around lithographically defined center frequencies, enables the fabrication of transmit and receive modules of the next-generation radio-frequency front ends on the same chip without adding fabrication steps.