VARIABLE SYMBOL-RATE DEMODULATORS FOR CABLE AND SATELLITE TV BROADCASTING

We present the design and the basic features of variable symbol-rate d emodulators for digital TV broadcasting by cable and satellite. The de modulators are fully compliant with the DVB Recommendations which were later published as ETSI standards. The satellite demodulator employs the QPSK signal constellation and can handle symbol rates up to 30 Mba ud. The cable demodulator is configurable to operate with all QAM sign al formats from 16-QAM to 256-QAM, and handles symbol rates up to 7 Mb aud which is the maximum possible symbol rate in an 8 MHz channel. Bot h demodulators employ polyphase filtering for variable symbol rate ope ration and fully-digital carrier recovery loops with an extended frequ ency acquisition range. In addition, the cable demodulator includes a blind equalizer with smooth transition to a conventional adaptation al gorithm after convergence.