Patent ID: 6025763
Filing Date: 2000-02-15
Classification: H03H

Abstract:
A resonator-type surface-acoustic-wave filter having at least one series-arm surface-acoustic-wave resonator and at least one shunt-arm surface-acoustic-wave resonator coupled in a ladder circuit configuration, at least one said series-arm surface-acoustic-wave resonator having an interdigital transducer and a pair of reflectors disposed on opposite sides of said interdigital transducer, wherein:at least one said series-arm surface-acoustic-wave resonator satisfies the following condition A:(condition A) said reflectors are separated from said interdigital transducer by a distance t of at least (N/2+0.55).lambda..sub.1 but not more than (N/2+0.81).lambda..sub.1, where N is an arbitrary non-negative integer, and .lambda..sub.1 is a wavelength of a surface acoustic wave excited by said series-arm surface-acoustic-wave resonator;and whereinevery said series-arm surface-acoustic-wave resonator has an interdigital transducer with electrode fingers mutually separated by a distance of .lambda..sub.1 /2;in every said series-arm surface-acoustic-wave resonator having reflectors, said reflectors have electrode fingers mutually separated by said distance of .lambda..sub.1 /2;every said shunt-arm surface-acoustic-wave resonator has an interdigital transducer with electrode fingers mutually separated by a distance of .lambda..sub.2 /2, where .lambda..sub.2 is a wavelength of a surface acoustic wave excited by said shunt-arm surface-acoustic-wave-resonator; andin every said shunt arm surface-acoustic-wave resonator having reflectors, said reflectors have electrode fingers mutually separated by said distance of .lambda..sub.2 /2.