| 摘要 |
PURPOSE:To realize improvement of the temperature characteristics by setting the optimum conditions excepting the temperature coefficient of the substrate when the decision is given to the frequency within the using frequency band of the dispersing elastic surface wave delay line. CONSTITUTION:Frequency fi is mixed with frequency (f) sent from local oscillator 10 through mixer 11 and with the use of dispersing elastic surface wave delay lines 12 and 14 with which a set of screen-roller type electrodes are distributed on substrate 1. Delay time tau1 is given to the signal of frequency f-fi via delay line 12 and then restored to the signal of frequency fi after adding frequency (f) sent from oscillator 10 and via mixer 13. The restored signal is then applied to delay line 14 to form the variable delay line with addition of the delay of time tau2. In case the frequency characteritics of lines 12 and 14 of such constitution are expressed by tau= af+b [(a),(b): constants] and a certain frequency fO which is within the using frequency band of lines 12 and 14 each is decided, constants (a) and (b) are set to the value approximate to -tauO/fO (tauO: delay time to fO) and the value approximate to 2tauO each. As a result, the temperature characteristics can be improved to secure the constant delay time. |
