Tuning control apparatus of receiver

Abstract

The output of a voltage controlled oscillator serving as a local oscillator is frequency divided by a prescaler and a programmable frequency divider, and the frequency divided output is applied to a phase locked loop including a phase comparator and a charge pump. An S curve signal obtained from a frequency discriminator is applied to an automatic frequency control loop including a window comparator and a charge pump. The outputs of these two charge pumps are applied through an analog switch to a common low-pass filter and the output of the low-pass filter is applied to the voltage controlled oscillator as a control voltage. A state of reception by the tuner is detected based on the output of an intermediate frequency amplifier and the analog switch is responsive to the detected output and a lock detected output of the phase locked loop. Accordingly, a control voltage obtained from the phase locked loop on the occasion of a station selecting operation or a control voltage obtained from the automatic frequency control loop on the occasion of the reception of the electric wave by the tuner, is switchably selected and is applied to the voltage controlled oscillator.