Front-end Of A Digital Atv Receiver

This paper describes the front-end of a digital ATV receiver. The front-end contains a tuner, a surface acoustic wave (SAW) filter, a downconverter, a vestigial sideband (VSB) demodulator, an analog-to-digital converter (ADC), and an on-board microprocessor. The signal level at the input of the ATV receiver, in the case of a terrestrial broadcast, can change by more than 80 dB. The level of the input signal can change rapidly due to plane jitter or dynamic ghost interference. The performance of the ATV receiver depends heavily on the accuracy and reaction time of the automatic gain control (AGC) system. The concept and algorithm for a digital delayed AGC was developed and investigated. A digital delayed AGC algorithm was implemented using an on-board microprocessor with data supplied by the VSB demodulator's AGC output. The front-end board was tested in the lab and in the field with real terrestrial ATV broadcasts and some of the results are presented.