Patent ID: 8090056

Claim:
A system comprising: a first complex multiplier and a second complex multiplier, the first complex multiplier configured to receive an input signal and provide a baseband I component signal, the second complex multiplier configured to receive the input signal and provide a baseband Q component signal; a first filter configured to filter the baseband I component signal; a second filter configured to filter the baseband Q component signal; an equalizer configured to equalize the filtered baseband I component signal and to equalize the filtered baseband Q component signal; a carrier recovery portion configured to generate a reference signal based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal; a first multilevel comparator configured to receive the equalized filtered baseband I component signal from the carrier recovery portion and provide an output I signal for further demodulation; a second multilevel comparator configured to receive the equalized filtered baseband Q component signal from the carrier recovery portion and provide an output Q signal for further demodulation; and a signal quality estimation circuit configured to estimate a signal quality based on the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal, the signal quality estimation circuit comprising: a distance calculator configured to determine a distance between an ideal symbol and a received symbol of the equalized filtered baseband I component signal and the equalized filtered baseband Q component signal; an average calculator configured to determine an average distance based on the distance from the distance calculator; the average distance being between successive received symbols and corresponding ideal symbols; and a comparator configured to compare the average distance to a predetermined threshold.