Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1997-03-06
1998-06-16
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310313B, 310313D, 333193, H01L 4104
Patent
active
057676089
ABSTRACT:
A surface acoustic wave (SAW) position-sensing device comprising a piezoelectric substrate, an input interdigital transducer (IDT) T formed on an upper end surface of the piezoelectric substrate, and an output IDT R formed on the upper end surface of the piezoelectric substrate such that the finger direction of the IDT R is slanting to that of the IDT T by an angle .alpha.. The thickness d of the piezoelectric substrate is larger than three times an interdigital periodicity P of the IDT T. An interdigital periodicity P.sub.N along the vertical direction to the finger direction of the IDT R is equal to the product of the interdigital periodicity P and cos .alpha.. An overlap length L.sub.P along the finger direction of the IDT R is equal to the product of an overlap length L of the T and sec .alpha.. When an electric signal is applied to the IDT T, the SAW is excited on the upper end surface of the piezoelectric substrate, and is transducer to electric signals E.sub.j with phases .theta..sub.j by the IDT R, the phases .theta..sub.j corresponding to positions F.sub.j. The total phase .SIGMA..theta..sub.j made by the phases .theta..sub.j, and the total electric signal .SIGMA.E.sub.j made by the electric signals E.sub.j are zero. The IDT T and R form minute propagation lanes Z.sub.j, corresponding to the positions F.sub.j, of the SAW on the upper end surface of the piezoelectric substrate. If touching a position F.sub.x on a minute propagation lane Z.sub.x, an electric signal E with a phase .theta. is delivered from the IDT R. The position F.sub.x corresponds to an electric signal E.sub.x with a phase .theta..sub.x, the electric signal .SIGMA.E.sub.j minus the electric signal E.sub.x being equal to the electric signal E, the phase .SIGMA..theta..sub.j minus the phase .theta..sub.x being equal to the phase .theta..
REFERENCES:
patent: Re33151 (1990-01-01), Adler
patent: 4293734 (1981-10-01), Pepper, Jr.
patent: 5679998 (1997-10-01), Toda
Budd Mark O.
Williams Timothy A.
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