| 摘要 |
PURPOSE:To measure a piezoelectric body substrate which has a relatively low electromechanical coupling coefficient with high accuracy without causing any characteristic deterioration by constituting the instrument of MF(matched filter) constitution which is tolerant to noises. CONSTITUTION:The instrument consists of a signal source 14 and the insulating substrate 13 which is provided with an input electrode 11 and an output electrode 12 made of interdigital electrodes and generates no SAW(surface acoustic wave). The electrode 12 has an array of taps 121 - 12a whose phases are nearly 0 or 180 deg. corresponding to codes 0 and 1 and the signal source 14 supplies a carrier to the electrode 11 after inverting the same code with the tap array or every other code, or imposing two-phase modulation with similar codes. Then the substrate 13 is pressed against a body 15 whose SAW propagation speed is to be measured in contact on the arrangement side of the electrodes 11 and 12 to obtain the MF constitution wherein the electrodes 11 and 12 and body 15 to be measured serve as a propagation medium for the SAW, thereby measuring the propagation speed. |
