DIGITAL TELEVISION RECEIVER

摘要

PURPOSE:To store an image free of distortions in a frame memory by providing an analog band pass filter and a waveshape forming circuit for constituting a horizontal phase synchronizing loop operating with the analog output as clocks. CONSTITUTION:Clocks are produced by a BPF180 and the waveshape forming circuit 181. With the clock frequency setting of NFH/FX (wherein N denotes the ratio of frequency division, FH horizontal frequency and FX the clock frequency derived from the crystal) the oscillation frequency at a digital oscillating circuit 125 equals NFH. This clock frequency is converted in a D/A converting circuit 127 into an analog frequency and the clock signal component is extracted at the BPF180 and sliced to produce clocks. Either the clock frequency of 13.5MHz and the crystal frequency of 25MHz, the Nyquist frequency is exceeded. High harmonics are produced by exciting a circuit 127 with pulses so that clocks of 13.5MHz are obtained.