Communications – electrical: acoustic wave systems and devices – Distance or direction finding
Patent
1997-03-06
1998-06-23
Pihulic, Daniel T.
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
367907, 310313R, H01L 4108
Patent
active
057712069
ABSTRACT:
An elastic wave position-sensing device comprising a piezoelectric substrate, an input interdigital transducer T formed on an upper end surface of the piezoelectric substrate, and an output interdigital transducer R formed on the upper end surface of the piezoelectric substrate such that the finger direction of the interdigital transducer R is slanting to that of the interdigital transducer T by an angle .alpha.. The thickness d of the piezoelectric substrate is smaller than an interdigital periodicity P of the interdigital transducer T. An interdigital periodicity P.sub.N along the vertical direction to the finger direction of the interdigital transducer 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 interdigital transducer R is equal to the product of an overlap length L of the interdigital transducer T and sec .alpha.. When an electric signal is applied to the interdigital transducer T, the elastic wave is excited in the piezoelectric substrate, and is transduced to electric signals E.sub.j with phases .theta..sub.j by the interdigital transducer R, the phases .theta..sub.j corresponding to positions F.sub.j on the upper- or a lower end surface of the piezoelectric substrate. 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 interdigital transducers T and R form minute propagation lanes Z.sub.j, corresponding to the positions F.sub.j, of the elastic wave in 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 interdigital transducer 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: 5679998 (1997-10-01), Toda
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