Surface Acoustic Wave Filters for Communication Systems

Abstract

Low insertion loss and good temperature stability are the main requirements for filters used in communication system front ends. These requirements severely limit the design options for SAW filters that can be used in modern communication systems. It should be noted that until recently SAW filters with a relative bandwidth of 1..10% and low losses, and most demanded for communication systems, had low-temperature stability. This was due to the temperature coefficients of waveguide material medium frequency of the SAW filters. Such materials are strong piezoelectrics niobate and lithium tantalate.

Research aimed at improving the temperature stability of devices based on lithium niobate and tantalate was started a long time ago. Still, only emerging new technologies have provided the possibility of solving this problem for mass production conditions. Currently, the input circuits of almost all mobile communication devices incorporate filters (duplexers) on SAW.

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