Patent ID: 7760821

Claim:
A method for identifying the impulse response of a data channel, the method comprising: using an apparatus comprising a controller, a sequence generator, and a correlator for: supplying to the data channel an input comprising a pseudo-random binary sequence of L symbols at a symbol rate of 1/T; producing a channel output by sampling a channel output signal corresponding to said input with a sampling interval T S =(q/p)T, where q and p are relative prime integers with q<p, and q and L are relative prime integers; producing p polyphase sequences from said channel output by selecting, for each polyphase sequence, every p th sample of said output, with a phase shift of one sample between successive polyphase sequences; producing a decimated binary sequence by selecting every q th symbol of the channel input; for each polyphase sequence, correlating that polyphase sequence with the decimated binary sequence, the two possible binary values being of equal magnitude and opposite sign for the correlation, and accumulating the correlation results to produce a correlated output sequence; and interleaving samples of the correlated output sequences in phase order of the corresponding polyphase sequences to produce the impulse response of the channel.