Coarse carrier phase correction system

Claim 2

A carrier phase offset correction system for use with a data receiver of the type that receives a data signal that has been transmitted at one or more prearranged rates wherein said correction system is comprised of: a first and second signal channel, each comprised of a demodulator means for receiving said data signal and for demodulating said data signal against a reference carrier signal, low pass filter means for filtering said demodulated signal, means for providing an output pulse each time the filtered signal from said low pass filter means crosses through a zero amplitude level at a rate higher than a preselected rate; a difference means for receiving the output pulses from said first and said second channel to proviDe an error signal indicative of the difference in carrier phase error between said first channel and said second channel; a reference carrier phase signal source; a phase modulator for receiving said reference carrier phase signal and for modulating the phase of said signal in response to said error signal; a phase offset means for receiving the modulated reference carrier phase signal and for offsetting said signal by a fixed increment to provide an offset reference carrier signal which is fed to the demodulator in said second signal channel against which the input data signal is demodulated, the demodulator of said second channel receiving the offset phase modulated carrier signal as the reference signal against which the input data signal is demodulated.

Claim 3

The system according to claim 1 wherein said first and second signal channel are each further comprised of: a narrowband filtering means for converting the output pulse train from said zero-crossing-to-impulse converter means into a signal level indicative of the phase error in said reference carrier signal.

Claim 4

A carrier phase offset correction system for use with a data receiver of the type that receives a data signal that has been transmitted at one or more prearranged baud rates wherein said correction system is comprised of: first and second demodulating means for demodulating said received data signal against a reference signal, the output of said correction system being taken from said first demodulator means; first and second zero-crossing detector means for receiving the demodulated baseband signal from said first and second demodulator means, respectively, and for providing output signals indicative of the zero-crossings of said demodulated baseband signal; rate means for limiting the provided output signals from said zero-crossing detector means to crossing signals having a rate of crossing greater than a preselected value; difference means for receiving the non-limited crossing signal from said first and said second zero-crossing detector means and for providing an error signal proportional to the difference between said output signals; a reference carrier signal source providing a carrier signal; a phase modulator receiving said provided carrier signal and modulating the phase of said carrier signal by an amount proportional to said error signal, said phase modulated carrier signal being fed to said first demodulating means as said reference signal; and phase offset means for receiving as an input said modulated reference carrier phase signal and for offsetting the phase of said modulated reference carrier signal by a fixed amount, said offset signal fed to said second demodulator as said reference signal.

Claim 5

A carrier phase offset correction system for use with a data receiver of the type that receives a data signal that has been transmitted at one or more prearranged baud rates wherein said correction system is comprised of: first and second demodulating means for demodulating said received data signal against a reference signal, the output of said correction system being taken from said first demodulator means; first and second zero-crossing detector means for receiving the demodulated baseband signal from said first and second demodulator means, respectively, and for providing output signals indicative of the zero-crossings of said demodulated baseband signal; rate means for limiting the provided output signals from said zero-crossing detector means to crossing signals having a rate of crossing greater than a preselected value; difference means for receiving the non-limited crossing signal from said first and said second zero-crossing detector means and for providing an error signal proportional to the difference between said output signals; a reference carrier signal source providing a carrier signal; a phase modulator receiving said provided carrier signal and modulating the phase of said carrier signal by an amount proportional to said error signal, said phase modulated carrier signal being fed to said first demodulating means as said reference signal; and phase offset means for receiving as an input said modulated reference carrier phase signal and for offsetting the phase of said modulated reference carrier signal by a fixed amount, said offset signal fed to said second demodulator as said reference signal.

Claim 6

The system according to claim 3 and further comprising: a narrowband filtering means for receiving the output signal from said rate means and for converting said output signals into signal levels indicative of the phase error in said reference carrier, said signal levels being fed to said difference means.

Claim 7

A carrier phase offset correction system for use with a data receiver of the type that receives a data signal that has been transmitted at one or more prearranged baud rates wherein said correction system is comprised of: first and second demodulating means for demodulating said received data signal against a reference signal, the output of said correction system being taken from said first demodulator means; a first and second zero-crossing detector for providing an output signal indicating the zero-crossing of the demodulated signals from said first and said second demodulating means, respectively; a first and second rate detector having as an input the demodulated signals from said first and said second demodulators, respectively, and providing an output signal when said demodulated signal passes through a zero reference at a rate greater than a preselected value; a first and second gate means reCeiving the output signals from said first and second zero-crossing detectors, respectively, and from said first and second rate detectors, respectively, and providing an output upon the simultaneous receipt of an output signal from said rate detector and said zero-crossing detector; difference means for receiving the output signal from said first and said second gate means and for providing an error signal proportional to the difference between said output signals; a reference carrier signal source providing a carrier signal; a phase modulator receiving said provided carrier signal for modulating the phase of said carrier signal by an amount proportional to said error signal, said phase modulated carrier signal being fed to said first demodulating means as said reference signal; and phase offset means for receiving as an input said modulated reference carrier phase signal, for offsetting the phase of said modulated reference carrier signal by a fixed amount, said offset signal fed to said second demodulator as said reference signal.

Claim 8

A carrier phase offset correction system for use with a data receiver of the type that receives a data signal that has been transmitted at one or more prearranged baud rates wherein said correction system is comprised of: first and second demodulating means for demodulating said received data signal against a reference signal, the output of said correction system being taken from said first demodulator means; a first and second zero-crossing detector for providing an output signal indicating the zero-crossing of the demodulated signals from said first and said second demodulating means, respectively; a first and second rate detector having as an input the demodulated signals from said first and said second demodulators, respectively, and providing an output signal when said demodulated signal passes through a zero reference at a rate greater than a preselected value; a first and second gate means reCeiving the output signals from said first and second zero-crossing detectors, respectively, and from said first and second rate detectors, respectively, and providing an output upon the simultaneous receipt of an output signal from said rate detector and said zero-crossing detector; difference means for receiving the output signal from said first and said second gate means and for providing an error signal proportional to the difference between said output signals; a reference carrier signal source providing a carrier signal; a phase modulator receiving said provided carrier signal for modulating the phase of said carrier signal by an amount proportional to said error signal, said phase modulated carrier signal being fed to said first demodulating means as said reference signal; and phase offset means for receiving as an input said modulated reference carrier phase signal, for offsetting the phase of said modulated reference carrier signal by a fixed amount, said offset signal fed to said second demodulator as said reference signal.

Claim 9

The carrier phase offset correction system of claim 5 wherein said first and second rate detectors are each comprised of: a differentiator for receiving said demodulated signal and for providing a signal proportional to the differential of said demodulated signal; a rectifier for rectifying said differential signal; and a threshold detector for providing an output signal when the amplitude of said rectified differential signal is above a preselected amplitude.

Claim 10

A carrier phase correction system according to claim 5 wherein said first and said second zero-crossing detectors are each comprised of: an amplifier for amplifying said demodulated signal; a limiter for converting said amplified signal into a square wave signal; and a differentiator for converting said square wave signal into output pulse signals corresponding to the zero-crossings of said demodulated signals.

Claim 11

The carrier phase offset correction system according to claim 5 and further comprising: a first and second narrowband filter means receiving the outputs from said first and second gate means, respectively, and for converting said output signals into signal levels indicative of the phase error in said reference carrier, said signal levels being fed to said difference means.