U.S. Philips Corporation

Ian Flinn

Robert Frederick Milsom

Robert J Murray

Surface acoustic wave bandpass transversal filters, e.g. television intermediate frequency filters, comprising a +.theta..degree. rotated Y-cut X-propagating lithium niobate substrate with .theta. in the range from 121.degree. to 127.degree., preferably 123.degree. to 125.degree.. For a suitable range of filter bandwidths (35 db bandwidth between 0.05 and 0.5) these substrates provide reduced degradation of the filter upper stopband predominantly due to indirect bulk shear waves in the frequency range from the passband up to the frequency where direct bulk longitudinal wave degradation becomes significant. This frequency range is 41.5 MHz to approximately 55 MHz for a U.K. system t.v. i.f. filter and is 60.25 MHz to approximately 90 MHz for a Japanese system t.v. i.f. filter.

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Crawley, United Kingdom

Ian Flinn