| 摘要 |
PURPOSE:To use only one matching inductor of a peripheral circuit per transducer even at a low frequency and wide band by making the admittance of a sending electrode and a reflecting electrode different from each other and deviating a geometrical phase difference from an odd number of multiple of 90 deg.. CONSTITUTION:The conductance of the transmission electrode and the reflecting electrode is made different from each other and the geometrical phase difference decided by the center distance of both the electrodes is deviated from an odd number of multiple of pi/2. Let the admittance of the transmission and reflection electrodes be Ci+jBill and Cq+jBq12 respectively, then the ratio Rp of the effective power converted into a surface acoustic wave by the transmission electrode and the reflection electrode is expressed in equation 1. When the constitution of both the electrodes is the same, the relation of Gi=Gq and Bi=Bq exists, the effective power of both the electrodes is equal and an inductor is required to obtain the unidirectionality. In making the conductance of both the electrodes different, an electric phase difference is caused without using the inductor, the geometrical phase difference is decided to make the surface acoustic wave energy propagated to both the directions of the electrode different thereby obtaining the unidirectionality.
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