PURPOSE: To generate a corrected reference subcarrier and to generate a subcarrier phase locked to the corrected reference subcarrier even when a characteristic change takes place due to a temperature change in a band pass filter(BPF) extracting the reference subcarrier from a video signal VIDEO.

CONSTITUTION: A BPF 21A extracts an original external reference subcarrier EXT-SCO included in a video signal VIDEO. A gradient circuit 212a comprising a diode 201, a resistor 202 and a capacitor 203 generates a gradient subcarrier SC in which the trailing of the subcarrier EXT-SC0 is subject to gradient. A base-emitter voltage VBE of a transistor(TR) 211 changes with temperature and its amplification factor is subject to change. Thus, a level adjustment circuit 212b including the TR 211 changes an amplitude of the subcarrier in response to a temperature change in the BPF 21A to provide an output of an external reference subcarrier EXT-SC. The subcarrier EXT-SC whose amplitude changes with temperature indicates it that the valid pulse width is changed at a threshold level and the subcarrier EXT-SC whose amplitude is adjusted and tilted in this way is equivalent to that the phase is adjusted substantially in the phase comparison in a phase locked loop circuit (PLL).