ABSTRACT GHz-range low-loss transducers and filters are required for communication systems, especially mobile telephone communication systems. Many types of low insertion-loss transducers and filters utilizing the high electromechanical coupling coefficient (K2) materials such as LiNbO3 and LiTaO3 have been developed. Unfortunately, these materials have large temperature coefficients of the frequency (TCF). In this paper, SAW substrates with high coupling coefficients and low propagation attenuations and small temperature coefficient of frequency at GHz-range are theoretically and experimentally investigated. The experimental results show very low propagation loss of 0.02dB/λ0 and larger K2 than those of the substrates of LiNb03 and LiTa03 at the TCF of below -5ppm/°C at 1~2 GHz-range. The low-loss filter results using internal reflection types of IDT show the insertion loss of about 2.9dB at 1 GHz and 4.9 dB at 2 GHz under the TCF's of 0 and +20 ppm/°C. These materials are applicable for devices at GHz-range because SiO2 thickness is very thin such as below 1 µm and the center frequency shift of the filter versus SiO2 thickness is very small.
© 1995, by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.