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Digital high definition television signal receiver with imaginary sample presence detector for quadrature amplitude modulation / vestigial sideband mode selection
Digital high definition television signal receiver with imaginary sample presence detector for quadrature amplitude modulation / vestigial sideband mode selection
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机译:带有虚拟样本存在检测器的数字高清电视信号接收器,用于正交幅度调制/残余边带模式选择
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摘要
A radio receiver for receiving a selected digital HDTV signal, irrespective of whether it is a complex-amplitude-modulation (QAM) or a vestigial sideband (VSB) signal, using the same tuner. The final IF signal from the tuner is digitized for application to in-phase and quadrature QAM synchronous detectors and to in-phase and quadrature VSB synchronous detectors. The carrier frequencies of the QAM and VSB final IF signals are regulated to be submultiples of symbol frequency by applying automatic frequency and phase control signals developed in the digital circuitry to a local oscillator of the tuner. The mean average energy in the output samples of the quadrature VSB synchronous detector is sensed for automatically switching the radio receiver reception mode, for operation in a VSB HDTV signal reception mode when the mean average energy is below a threshold level, and for operation in a QAM signal reception mode when the mean average energy is not below the threshold level.
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