Phase tracking network

An apparatus adapted to receive an input signal which contains phase error wherein the apparatus provides a variable reference signal which is an estimate of the level of the input signal, said apparatus comprising:

• phase correction means responsive to the input signal for correcting at least some of the phase error to provide a phase corrected signal;
• detector means responsive to the phase corrected signal for providing a detected signal;
• error calculator means responsive to at least one of the phase corrected signal and the detected signal to provide a first signal which is related to said variable reference signal and first means responsive to the first signal for providing a phase error signal;
• said first means including means for dividing the first signal by the variable reference signal whereby the phase error signal is made substantially independent of variations in the reference signal;
• and
• said phase correction means including means responsive to the phase error signal for at least partially correcting of the phase error in the input signal.

A method of correcting the phase error of an input signal which is representative of data wherein a receiver provides a variable reference signal which is an estimate of the level of the input signal, said method comprising:

• correcting at least some of the phase error of the input signal to provide a phase corrected signal;
• detecting the data in the phase corrected signal to thereby provide a detected signal;
• using at least one of the phase corrected signal and the detected signal to provide a first signal which is approximately equal to the variable reference signal times the phase error of the phase corrected signal;
• dividing the first signal by the variable reference signal to provide a phase error signal which is substantially independent of variations in the reference signal;
• and
• using the phase error signal to at least assist in the correcting of the phase error in the input signal.

A method of correcting the phase error of an input signal which is representative of data comprising:

• correcting at least some of the phase error to provide a phase corrected signal having components in first and second channels;
• detecting the data in the phase corrected signal to provide a detected signal having first and second components in the first and second channels, respectively, each of said components of the detected signal having an ideal value which can vary from positive to negative and at least at times equals zero;
• providing a first control signal representing a first fixed value, zero, and a second fixed value when the first component of the detected signal is ideally positive and not zero, ideally zero, and ideally negative and not zero, respectively, one of said first and second fixed values being positive and the other of said first and second fixed values being negative;
• providing a second control signal representing a third fixed value, zero, and a fourth fixed value when the second component of the detected signal is ideally positive and not zero, ideally zero, and ideally negative and not zero, respectively, one of said third and fourth fixed values being positive and the other of said third and fourth fixed values being negative;
• providing a phase error signal in accordance with a relationship having the values of said control signals in different terms of the numerator and algebraically summing said terms whereby the phase error signal contains substantially no noise from the first channel at least when the first component of the detected signal is zero and which contains substantially no noise from the second channel at least when the second component of the detected signal is zero;
• and
• using the phase error signal to at least partially correct the phase error of the input signal.