Patent ID: 8879669

Claim:
A QAM channel monitor comprising: a QAM demodulator for demodulating a QAM signal and generating first and second diagnostic data for diagnostics of demodulation of the QAM signal; an impairment detector coupled to the QAM demodulator, configured for providing an impairment detection signal upon detecting that the first diagnostic data crosses a threshold; and a memory unit coupled to the QAM demodulator, configured for capturing at least a portion of the second diagnostic data upon receiving a triggering signal comprising the impairment detection signal or based on the impairment detection signal, the memory unit comprising: a memory buffer configured for continuously writing the second diagnostic data therein; and a snapshot controller coupled to the memory buffer, configured for receiving the triggering signal and for controlling the memory buffer to capture at least one of first and second portions of the second diagnostic data received before and after the triggering signal was received, respectively.