Low loss wide band filters and resonator filters using high temperature stable high electromechanical coupling surface acoustic wave substrates

Abstract

The important properties required for SAW substrates are a large electromechanical coupling coefficients (k/sup 2/), small temperature coefficient of frequency (TCF), low propagation loss, etc. LiNbO/sub 2/ has good properties as the SAW substrate with a large size. Unfortunately LiNbO/sub 3/ possesses the large values of TCF. We developed the SiO/sub 2//Rotated Y-cut, X-Propagating LiNbO/sub 3/ leaky SAW substrates with a large k/sup 2/(over 0.2) and zero TCF at very thin thickness of SiO/sub 2/ of H//spl lambda/ = 0.2 (H:SiO/sub 2/ film thickness, /spl lambda/ :SAW wave-length) and zero propagation attenuation in the case of moralized surface. In this paper, the theoretical and experimental results of SAW filters, resonators and resonator filters are described. The low loss filters using FEUDT showed the insertion loss of below 2dB at the center frequency of 400MHz and bandwidth of 20MHz. Also, the resonator showed the band width of 70MHz at the center frequency of 500MHz and resonator filters showed the band width of 80MHz at the center frequency of 500MHz.