Abstract :
A single VLSI chip solution for variable rate demodulation of 16/64/256 QAM modulated signals is described. This chip is suitable for receiving QAM modulated signals over cable and MMDS (multi-point microwave distribution system} channels. The IC is capable of working both in bandpass sampling mode, and quadrature sampling mode. The functional blocks of the chip inc1ude: a digital decimation filter for variable symbol rate demodulation, digital receive filtering for matched filtering, a fully adaptive decision-feedback (DFE) equalizer to compensate for the micro-relections, dc offset correction to remove baseline wander effects, quadrature imbalance compensation, digitally implemented carrier recovery loop, automatic gain control (AGC), and digitally implemented symbol timing loop. The chip was implemented in 3.3 volt, 0.5 micron CMOS technology, and has been successfully tested in various laboratory experiments and field trials.
