HDTV SIGNAL RECEIVER WITH IMAGINARY SAMPLE PRESENCE DETECTOR FOR QAM/VSB MODE SELECTION

摘要

A wireless receiver for receiving a selected digital HDTV signal, regardless of whether the selected digital HDTV signal is a quadrature amplitude modulated (QAM) signal or a residual sideband (VSB) signal using the same tuner. The final IF signal from the tuner is digitized for application to in-phase and quadrature QAM sync detectors and in-phase and quadrature VSB sync detectors. The carrier frequency of the QAM and VSB final IF signals is adjusted to be a divisor of the symbol frequency by applying an automatic frequency phase control signal developed in the digital circuit to the tuner's local oscillator. To operate in the VSB HDTV signal reception mode when the average energy is below the threshold level and to operate in the QAM HDTV signal reception mode when the average energy is not below the threshold level, the average energy of the output samples of the right-angle VSB sync detector automatically changes to the wireless receiver reception mode. Detected to switch to