Demonstration of Spurious-Free and Low-Loss X-Band SAW Filter

In this work, the authors explore the possibilities of scaling the shear horizontal surface acoustic wave (SH-SAW) resonators and filter to the X-band by designing the high-performance hetero-substrate. Through finite element simulation, high-velocity, low-loss and high-temperature stability LiTaO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>/SiC hetero-substrate, and the interdigital transducers (IDT) are designed to achieve the high-frequency response and avoid the appearance of spurious modes. The series and shunt SH-SAW resonators operating at high frequencies up to 9~10 GHz exhibit decent coupling, quality factors of 500 and spurious-free responses. The fabricated SAW filter shows an ultra-high center frequency of 9.51 GHz, a 3-dB bandwidth of 424 MHz, an insertion loss of 1.92 dB, a spurious-free frequency response in the range of 1~11 GHz. The temperature coefficients of frequency of filter are also measured, exhibiting small frequency drift and stable frequency response of the passband. These high-performance SAW devices based on the LiTaO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>/SiC hetero-substrate show great potential to develop the advanced communication systems.