DIGITAL HIGH-RESOLUTION TELEVISION SIGNAL RECEIVER HAVING IMAGINARY-NUMBER-SAMPLE SENSING SENEOR FOR PERFORMING MODE SELECTION OF QUADRATURE-AMPLITUDE/VESTIGIAL-SIDEBAND MODULATIONS

摘要

PURPOSE: To provide a radio receiver for receiving a selected digital HDTV signal in spite of whether the selected digital HDTV signal to utilize the same tuner is a quadrature amplitude modulation(QAM) signal or a residual side band (VSB) signal. CONSTITUTION: A final IF signal from the tuner is digitized for impression to an in-phase and orthogonal phase QAM synchronism detector and an in-phase and orthogonal phase VSB synchronism detector. The carrier frequency of QAM and VSB final IF signal is adjusted so as to be the divisor of symbol frequency by impressing an automatic frequency phase control signal developed by a digital circuit to the local oscillator of tuner. Because of operation in VSB HDTV signal reception mode when average energy is lower than a threshold level and because of operation in QAM HDTV signal reception mode when the average energy is not lower than the threshold level, average energy of output sample from the orthogonal VSB synchronism detector is searched for automatically switching a radio receiver reception mode.