Wireless receiver for receiving residual sideband and quadrature amplitude modulated digital high quality television signals

摘要

A wireless receiver for receiving a selected digital HDTV signal, regardless of whether the selected digital HDTV signal is a complex amplitude modulated (QAM) signal or a residual sideband (VSB) signal using the same tuner. The tuner provides the final IF signal in the 6 MHz frequency band, with its lowest frequency not exceeding 2.38 MHz. In a digital synchronization circuit, the final IF signal is digitalized to synchronize to the baseband, showing a 2.375 MHz difference between the carrier frequency of the QAM signal and the carrier frequency of the VSB signal. The carrier frequencies of the QAM final IF signal and the VSB final IF signal are controlled to be a divisor of the symbol frequency by applying the automatic frequency and phase control signal developed in the digital circuit to the local oscillator of the tuner. The presence of a pilot carrier accompanying the selected VSB HDTV signal is detected to automatically switch the wireless receiver to operate in the VSB receive mode. The absence of a pilot carrier accompanying the selected QAM HDTV signal is detected to automatically switch the wireless receiver for operating in the QAM signal reception mode.