Spurious-Free and Low-Loss Surface Acoustic Wave Filter Beyond 5 GHz

In this work, the high-frequency shear horizontal surface acoustic wave (SH-SAW) devices are demonstrated based on the high-velocity, low-loss and high-temperature stability LiTaO
3
/SiC hetero-substrate. Through finite element simulations, the ratio of the LiTaO
3
thickness to interdigital transducers (IDT) pitch is specially designed to achieve high-frequency response and avoid the appearance of the Rayleigh spurious mode. Besides, the double piston IDT is adopted to suppress transverse modes. The series and shunt SH-SAW resonators operating at high resonant frequencies up to 4.9~5.2 GHz exhibit high quality factors of more than 1700 and suppressed spurious modes. The fabricated SAW filter shows an ultra-high center frequency of 5.1 GHz, a 3-dB bandwidth of 251 MHz, a low minimum insertion loss of 0.98 dB, a spurious-free frequency response and a sufficient out-of-band rejection (>32 dB) in the range of 0.5~6.5 GHz.