| 摘要 |
PURPOSE:To prevent deterioration in signal quality by providing an input electrode exciting a surface acoustic wave and an output electrode converting the surface acoustic wave into an electric signal to a piezoelectric substrate and using plural taps for the input output electrodes. CONSTITUTION:Let a length of an output electrode 13 in the direction of propagation of a surface acoustic wave be L, a transmission speed of an input signal inputted to an input electrode 12 be A (bits/sec), a transmission speed of the surface acoustic wave be V(m/sec), a length of inter-tap space be DELTA1, then the relation of 2V/A=L+DELTA1 is satisfied. When a signal is applied to the electrode 12, the surface acoustic wave is excited and propagated to the electrode 13. When the phase of the signal inputted to taps 1-N and the phase of the signal inputted to taps N+1-2N are in-phase, correlation peaks are overlapped in phase and a larger peak is obtained. On the other hand, when the phases of two signals are opposite to each other, the correlation peaks are opposite to each other and cancelled together. Thus, data are easily demodulated by having only to detect an output level of the surface acoustic wave element. |
