MULTILEVEL QAM DEMODULATOR VLSI WITH WIDE-BAND CARRIER RECOVERY AND DUAL EQUALIZING MODE

A 16-/64-/256-quadrature amplitude modulation (QAM) demodulator LSI wi th an all-digital carrier-recovery loop including a novel phase detect or and a fractionally/symbol-spaced equalizer is described. The phase detector, which decides the transmitted symbol from received signal po wer, detects phase errors up to +/-45 degrees and enables the loop to internally eliminate the +/-80 kHz carrier-frequency offset. The fract ionally spaced equalizer is implemented at the same clock rate as the symbol-spaced equalizer by increasing only mnltiplexers and flip-flops , though the former theoretically requires an operation twice as fast as the latter. A large scale integrator (LSI) operating at a symbol ra te up to 8 MBaud is successfully implemented. The 0.5-mu m CMOS three- metal technology is used to implement 880 000 transistors in a die siz e of 12.87 x 12.49 mm(2).