PLL circuit and television receiver having same and beat reducing method for television receiver

摘要

A PLL circuit is used for a super-heterodyne television receiver. In the PLL circuit, a reference signal oscillator circuit generates a reference signal, and the reference signal is compared to a LO signal in a phase comparator. The phase comparator includes (i) an oscillating circuit, (ii) a series circuit of a correcting capacitor and an oscillator corresponding to a predetermined IF signal frequency, (iii) another correcting capacitor, and (iv) a switch. The switch is turned ON or OFF only when receiving a particular channel in which interference occurs, so as to shift the frequency of the reference signal by several ten kHz. This reduces beats in a particular channel, and prevents deterioration of picture quality in other channels. That is, interference in a particular channel can be reduced without causing any adverse effects in other channels having a relatively high frequency.