U.S. Philips Corporation

Martin Redwood

Richard F Mitchell

Frederick Warren Smith

Richard Stevens

Philip D White

John S Palfreeman

An acoustic wave resonator device comprises a substrate carrying a pair of spaced apart reflectors forming a resonant cavity that supports only three adjacent distinct resonant mode frequencies. An interdigital transducer is disposed on the substrate between the reflectors and includes an array of electrodes symmetrically arranged relative to a central point of the cavity to form a plurality of electrode pairs with the electrodes of each pair equally spaced on opposite sides of the central point. The central point of the cavity coincides with a node or an anti-node of the standing wave. If the two electrodes of each electrode pair are connected to the same terminal then the transducer has zero net coupling with one set of alternate modes of the cavity, whereas if said two electrodes are connected to opposite terminals then the transducer has zero net coupling with the other set of alternate modes.

Acoustic wave devices

An acoustic wave resonator device includes two pairs of coupled spaced apart reflectors which define two resonant cavities. The two cavities are each provided with two interdigital transducers which provide intercavity coupling. Additional reactance coupling between the transducers in one cavity combines with the equivalent cavity reactance to provide series or parallel resonance at a selected pole frequency.

A surface acoustic wave band-pass filter comprising a piezoelectric substrate having on one surface first and second SAW resonators tuned to the same frequency and coupled together. An input transducer is coupled to the first resonator and an output transducer is coupled to the second resonator. Each resonator is preferably formed by two spaced apart aligned grating reflectors and the two resonators are preferably coupled by an array of discrete parallel metallic strips extending between the two cavity resonators.

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Sevenoaks, United Kingdom

Martin Redwood