| 摘要 |
PURPOSE:To decrease the number of connecting terminals for input/output, by using the number of pulses as digital signals in a surface acoustic wave device for D/A converter and converting the number of pulses into an analog quantity. CONSTITUTION:In analog-converting the number of pulses up to N, the number of pairs of a comb type electrode 2 for surface acoustic wave excitation of a normal comb-shaped electrode of the surface acoustic wave device is designated as M(M=1,2-) and the number of pairs of a comb-shaped electrode 3 for surface acoustic wave detection is designated as N+M-1 or over, and the comb- shaped electrode for exciting surface acoustic is driven by a pulse circuit 4 where the period of pulse generation is KT0 (K=1,2-, and T0 is delay time for one pair). Thus, the number of pulses is analog-converted by using the function of addition of the comb-shaped electrodes. The number of pairs of the comb- shaped electrode 3 has only to be increased by N-1, by summing the number of pulses without fail, because the surface acoustic wave having the number of waves N with one driving pulse is excited and propagated, where the number of pairs of the comb-shaped electrode 2 for exciting surface acoustic wave is designated as N1. |
