| 摘要 |
PURPOSE:To prevent the fluctuation of the count start frequency due to the fluctuation of the oscillation signal energy by controlling the peak value counting of the oscillation signal which passed through the comb-line filter via the frequency of the resonator. CONSTITUTION:The output signal of local oscillator 1 is supplied to detector 3 via comb-line filter 2 to obtain the detection signal corresponding to the amplification component of the oscillation signal. The emerging frequencies of the detection signal's peak value are counted (7) while the control voltage of oscillator 1 is being swept (8), and the sweep of the control voltage is stopped when the count value reaches the fixed value. Counter 7 starts counting after the oscillation frequency generated according to the sweep becomes in agreement with the fixed resonance frequency of resonator 12. At the same time, the tooth-type electrodes forming filter 2 and resonator 12 are provided on the common piezoelectric substrate to make equal the frequency shift direction caused by the temperature change and thus to revent the malfunction. |
