High temperature stable GHz-range low-loss wide band transducers and filter using SiO2/LiNbO3,LiTaO3

SAW substrates with high coupling coefficients, low propagation attenuations, and small temperature coefficients in the GHz frequency range are theoretically and experimentally investigated. The experimental results show a very low propagation loss of 0.02 dB/λ₀ and larger K² than those of the substrates of LiNbO₃ and LiTaO₃ at temperature coefficients of the frequency (TCFs) of below -5 p.p.m./°C at the 1~2-GHz range. The low-loss filter results using internal reflection types of IDT show an insertion loss of about 2.9 dB at 1 GHz and 4.9 dB at 2 GHz under TCFs of 0 and +20 p.p.m./°C. These materials are applicable for devices at GHz range because SiO₂ thickness is very thin and the center frequency shift of the filter vs. SiO₂ thickness is very small