Design of surface acoustic wave filters using layer diamond structures with zero temperature coefficient of delay

The (100) ZnO/Cu IDTs/(100) AlN/diamond structures is presented in this study to retain a zero temperature coefficient of delay (TCD) along with a larger coupling coefficient and a higher phase velocity such that it can be employed to design wide-band RF filters for the long term evolution (LTE) wireless communication applications. With the optimized AlN and ZnO films thickness ratio of 3.333 and 0.17, and Cu electrode thickness ratio of 0.093, respectively, Sezawa mode in the (100) ZnO/Cu IDTs/(100) AlN/diamond structures possesses the phase velocity of 5672.05 m/s, coupling coefficient of 6.97%, and reflectivity of 0.15. The tailored ladder filter using these coupling-of-mode (COM) parameters yields a RF filter operating at 2535 MHz with 2.1 dB bandwidth of 74.2 MHz, insertion loss of 0.765 dB, and sidelobe suppression of 55.6 dB.