Study of Monolithic Multiband SAW Filters for S-Band

In this work, a set of resonators covering the S-band (2-4 GHz) in frequency was prepared based on 42°YX LiTaO3/SiC substrates. The fabricated SH-SAW resonators operate in the S-band with high quality (Q) factors of 550–2114 and electromechanical coupling coefficients (K<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) of 8.30%–9.68%. Then, monolithic multiband filters with full S-band coverage were designed and prepared by adjusting IDT period of the resonators. All filters have the same electrode thickness (120 nm Al) and film thickness (510 nm) and are prepared using the same set of experimental procedures. The S-band filters show low insertion loss (IL) of 0.67–1.61 dB, 3-dB fractional bandwidth (FBW) of 3.71%–5.63%, and out-of-band (OoB) rejection larger than 28 dB. The frequency drifts of resonators and filters were also measured. The results show the excellent temperature stability of the fabricated devices. These demonstrated SAW devices with excellent comprehensive performances show the great potential of LiTaO3/SiC as the platform for future wireless communications.