Acoustic surface wave device

Claim 2

An acoustic surface wave device comprising a body of piezoelectric material on one surface of which is arranged a first and a second transducer for respectively launching and receiving an acoustic surface wave propagated on said surface, in which each transducer includes at least one interdigital electrode array, one of said transducers including two extra electrodes on said surface of the body, each of said extra electrodes being positioned near a respective siDe of said one transducer in a direction approximately perpendicular to the surface wave propagation direction but electrically connected to the respective opposite side of said one transducer, so that when both transducers are operated in a push-pull mode each extra electrode is always of opposite polarity to the adjacent side of the one transducer so as to substantially reduce unwanted capacitive signal breakthrough from the launching to the receiving transducer.

Claim 3

An acoustic surface wave device as claimed in claim 1, in which the electrical connections between the extra electrodes and the respective opposite sides of said one transducer are formed on the surface of the body without cross-overs.

Claim 4

An acoustic surface wave device as claimed in claim 1 modified so that the first and second transducers are respectively arranged for receiving and launching an acoustic surface wave.

Claim 5

An acoustic surface wave device comprising a body of piezoelectric material having an acoustic surface wave propagation surface, first and second transducers each comprising at least one interdigital electrode array positioned on said propagation surface for respectively launching and receiving an acoustic surface wave on said surface, a first auxiliary electrode positioned on said surface near one side of one of said transducers and out of the surface wave propagation path, means electrically connecting the first auxiliary electrode to the opposite side of said one transducer, a second auxiliary electrodes positioned on said surface near the opposite side of said one transducer and out of the surface wave propagation path, and means electrically connecting the second auxiliary electrode to the one side of said one transducer whereby push-pull operation of said one transducer causes each auxiliary electrode to be of opposite electrical polarity to the adjacent side of the one transducer thereby to reduce capacitive signal breakthrough between the launching and receiving transducers.

Claim 6

An acoustic surface wave device comprising a body of piezoelectric material having an acoustic surface wave propagation surface, first and second transducers each comprising at least one interdigital electrode array positioned on said propagation surface for respectively launching and receiving an acoustic surface wave on said surface, a first auxiliary electrode positioned on said surface near one side of one of said transducers and out of the surface wave propagation path, means electrically connecting the first auxiliary electrode to the opposite side of said one transducer, a second auxiliary electrodes positioned on said surface near the opposite side of said one transducer and out of the surface wave propagation path, and means electrically connecting the second auxiliary electrode to the one side of said one transducer whereby push-pull operation of said one transducer causes each auxiliary electrode to be of opposite electrical polarity to the adjacent side of the one transducer thereby to reduce capacitive signal breakthrough between the launching and receiving transducers.

Claim 7

An acoustic surface wave device as claimed in claim 4 wherein said electrical connecting means comprise first and second electric conductors formed on the propagation surface without any crossovers.