High temperature stable GHz-range low-loss wide band transducers and filter using SiO/sub 2//LiNbO/sub 3/,LiTaO/sub 3/

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/ lambda /sub 0/ and larger K/sup 2/ than those of the substrates of LiNbO/sub 3/ and LiTaO/sub 3/ at temperature coefficients of the frequency (TCFs) of below -5 p.p.m./ degrees C at the 1 approximately 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./ degrees C. These materials are applicable for devices at GHz range because SiO/sub 2/ thickness is very thin and the center frequency shift of the filter vs. SiO/sub 2/ thickness is very small.<
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