Method and device for determining the phase intercept in a system employing phase-shift keying modulation

A method for deriving a signal from which the phase intercept value of a transmission channel at a given frequency can be determined, comprising the steps of:

• generating a mesurement signal having sinusoidal components at a given frequency and upper and lower frequencies spaced equally from the given frequency;
• transmitting the measurement signal over the transmission channel to a receiving unit;
• operating on the received measurement signal to extract signals proportional to the instantaneous phases of the received measurement signal at the given, upper and lower frequencies by
• sampling the received measurement signal at the signaling rate,
• converting the sampled signal to a digital format,
• separating the digitized, sampled signal into in-phase and quadradure components,
• filtering the separated components to derive the in-phase and quadrature components at the given, upper and lower frequencies, and
• combining the in-phase and quadrature components at each of the frequencies to derive the instantaneous phase signals for each of the frequencies;
• combining said instantaneous phase signals and a signal proportional to the difference between the upper and lower frequencies to derive a signal proportional to the slope of the channel in the region defined by the upper and lower frequencies;
• and
• operating on the instantaneous phase signals, the slope signal and signals proportional to the signaling rate and the given frequency to derive the signal from which the phase intercept value can be determined, said last-named step including the further steps of
• generating a first signal proportional to the difference between the instantaneous phase signals for the upper and lower frequencies,
• generating a second signal proportional to the product of said first signal, the given frequency and the signaling rate,
• generating a third signal proportional to the generated slope signal,
• generating a fourth signal proportional to the sum of said second signal and the instantaneous phase signal for the given frequency, and
• subtractively combining said third and fourth signals to produce the signal from which the phase intercept value can be determined.

A system for initializing a receiver to reduce the effects of phase intercept caused by transmission channel distortion, said system including:

• means for generating a measurement signal for transmission on said channel at a given signaling rate, the measurement signal having components at a given frequency and at upper and lower frequencies spaced uniformly from the given frequency;
• means for receiving said measurement signal and for extracting therefrom signals proportional to the instantaneous phases of the received signal at the given, upper and lower frequencies;
• means connected to said extracting means for generating a signal proportional to the slope of said channel in the region defined by the upper and lower frequencies as a function of the values of the three instantaneous phase signals and the difference between the upper and lower frequencies;
• means connected to said generating means for deriving the phase intercept signal as a function of the slope signal, the three instantaneous phase signals, the signaling rate and the given frequency;
• and
• data detection means including a filter having one input from said signal deriving means and an output which is subtractively combined with received data signals and switching means for isolating the data detection means from the data path during an initialization phase while connecting the filter to the output from said signal deriving means.

A method for initializing a receiver to reduce the effects of phase intercept caused by transmission channel distortion, said method including the steps of:

• generating a measurement signal having sinusoidal components at a given frequency and upper and lower frequencies spaced equally from the given frequency;
• transmitting the measurement signal over the transmission channel to a receiving unit;
• operating on the received measurement signal to extract signals proportional to the instantaneous phases of the received measurement signal at the given, upper and lower frequencies;
• combining said instantaneous phase signals and a signal proportional to the difference between the upper and lower frequencies to derive a signal proportional to the slope of the channel in the region defined by the upper and lower frequencies;
• operating on the instantaneous phase signals, the slope signal and signals proportional to the signaling rate and the given frequency to derive the signal from which the phase intercept value can be determined;
• and
• setting the output of a linear filter in a feedback loop to provide a compensating signal proportional to the derived phase intercept signal, the output being subtracted from applied data during post-initialization receiver operation.