| 摘要 |
<p>The circuit is specially intended for receivers having narrow-band carried filters. Such receivers usually have a mixing phase controlled by an oscillator, at least one filter for filtering out the intermediate frequency signals and a demodulator. The sharpness tuning is effected by way of a closed loop regulation. In one embodiment the mean value of the exit voltage of the demodulator is formed and compared with a desired voltage which gives the reference position of the intermediate frequency signal. The frequency of the oscillator is readjusted on the basis of the difference between the mean value and the desired voltage value. In another embodiment the mean value of the intermediate frequency is formed and compared with a desired frequency which gives the reference position of the intermediate frequency. The frequency of the oscillator is then readjusted on the basis of the difference between the mean value of the intermediate frequency and the desired frequency.</p> |
