BAND SWITCHING FILTER USING SURFACE ACOUSTIC WAVE RESONATOR, AND ANTENNA DUPLEXER USING THE FILTER

摘要

PROBLEM TO BE SOLVED: To miniaturize a band switching filter by miniaturizing a resonated and also reducing the number of stages in a filter by switching a band and to provide an antenna duplexes using the filter. SOLUTION: In this band switching filter, a resonance circuit consisting of a surface acoustic wave resonator 11, a switching element 13 and an impedance element 12 is installed and only one of two different bands is selectively made to pass through by one filter. The connection state of the surface acoustic wave resonator 11 and the impedance element 12 is switched by the shorting/ opening of the switching element 13. The parallel resonance point of the surface acoustic wave resonator 11 is moved to the other arbitrary resonance point.