High-Performance N77 Band Filters on Sapphire-based Heterogenous Substrates

This work demonstrates two fifth-generation (5G) N77 band shear horizontal surface acoustic wave (SH-SAW) filters with high-frequency and low insertion loss on sapphire-based heterogeneous substrates, including LiTaO3-on-sapphire (LTOS) and LiNbO3-on-sapphire (LNOS) substrates. The LTOS-based resonators maintain a high Q value above 3 GHz. The LTOS-based filter exhibits a small minimum insertion loss of only 0.86 dB at 3.6 GHz. Resonators on LNOS exhibit an excellent electromechanical coupling coefficient (k²) larger than 30%. The filter on LNOS exhibits a broad 3-dB bandwidth (BW3dB) of 603 MHz near 4 GHz with low insertion loss. After optimizing the structure and manufacturing process, SH-SAW filters on sapphire-based heterogeneous substrates will have great application potential in 5G N77 bands.