Data-aided carrier tracking loops

Claim 2

In a phase-locked loop having a conventional d-c control signal fed back to a voltage controlled oscillator for tracking a carrier signal applied to said loop in an angle modulated communications system having said carrier signal modulated by at least one intelligence modulated subcarrier, the improvement comprising: means for phase-shifting the a-c output of said oscillator; means for multiplying said carrier signal by the output signal of said phase-shifting means to produce a product signal; means for delaying said product signal by a delay time equal to the reciprocal of the intelligence rate in one subcarrier modulated onto said carrier signal to provide a delayed product signal; means for forming a signal representing an estimate of said modulated subcarrier power as the product of demodulated subcarrier and demodulated intelligence; means for multiplying said delayed product signal by said power estimate signal to produce a final product signal; means for filtering said final product signal to produce a d-c component signal proportional to the power of said modulated subcarrier; and means for adding said d-c component signal to said control signal fed back to said voltage controlled oscillator.

Claim 3

The improvement defined by claim 1 wherein said means for forming said signal representing an estimate of said modulated subcarrier power comprises: means for demodulating said carrier signal to obtain a first signal representing an estimate of said subcarrier modulated onto said carrier; means for demodulating said subcarrier signal to obtain a second signal representing an estimate of said intelligence modulated onto said subcarrier; and means for multiplying together said first and second signals.

Claim 4

In a phase-locked loop having a conventional d-c control signal fed back to a voltage controlled oscillator for tracking a carrier signal applied to said loop in an angle modulated communications system having said carrier signal modulated by a plurality of intelligence modulated subcarriers, the improvement comprising: means for multiplying said carrier signal by the output signal of said oscillator to produce a carrier product signal; means for forming a power estimate signal representing an estimate of the power of said intelligence modulated subcarriers as the combined product of demodulated subcarriers and demodulated intelligence signals, said estimate forming means including means for aligning the phases of demodulated subcarriers and demodulated intelligence signals; means for delaying said carrier product signal by a period sufficient to align said carrier product signal with said power estimate signal; means for multiplying said delayed carrier product signal by said power estimate signal to produce a final product signal; means for filtering said final product signal to produce said d-c component signal proportional to the power of said modulated subcarriers; and means for adding said d-c component signal to said control signal fed back to said voltage controlled oscillator.

Claim 5

In a phase-locked loop having a conventional d-c control signal fed back to a voltage controlled oscillator for tracking a carrier signal applied to said loop in an angle modulated communications system having said carrier signal modulated by a plurality of intelligence modulated subcarriers, the improvement comprising: means for multiplying said carrier signal by the output signal of said oscillator to produce a carrier product signal; means for forming a power estimate signal representing an estimate of the power of said intelligence modulated subcarriers as the combined product of demodulated subcarriers and demodulated intelligence signals, said estimate forming means including means for aligning the phases of demodulated subcarriers and demodulated intelligence signals; means for delaying said carrier product signal by a period sufficient to align said carrier product signal with said power estimate signal; means for multiplying said delayed carrier product signal by said power estimate signal to produce a final product signal; means for filtering said final product signal to produce said d-c component signal proportional to the power of said modulated subcarriers; and means for adding said d-c component signal to said control signal fed back to said voltage controlled oscillator.

Claim 6

The combination of claim 3 wherein said means for forming said power estimate signal comprises: means for separately demodulating said intelligence modulated subcarriers to obtain signals representing estimates of said subcarriers modulated onto said carrier; means for separately demodulating said subcarriers to obtain signals representing estimates of said intelligence signals modulated onto said subcarriers; means for multiplying said estimate signal of each subcarrier by said estimate signal of its intelligence signal to obtain product signals; a plurality of delay means for delaying each product signal by a period equal to the intelligence rate of its intelligence signal; and means for multiplying together the output signals of said plurality of delay means.

Claim 7

In a phase-locked loop having a control signal fed back to a voltage controlled oscillator for tracking a carrier signal applied to said loop in an angle modulated communications system having said carrier signal modulated by at least two intelligence signal modulated subcarriers, a quadrature channel added to said phase-locked loop, comprising: means for multiplying said carrier signal by the output signal of said oscillator to produce a carrier product signal; means for forming a power estimate signal representing an estimate of the power of said two intelligence modulated subcarriers as the combined product of demodulated subcarriers and demodulated intelligence signals, said estimate forming means including means for aligning the phases of demodulated subcarriers and demodulated intelligence signals; means for delaying said carrier product signal by a period sufficient to align said carrier product signal with said power estimate signal; means for multiplying said delayed carrier product signal by said power estimate signal to produce a final product signal; means for filtering said final product signal to produce a d-c signal proportional to the power of said modulated subcarriers; and means for adding said d-c signal to said control signal fed back to said oscillator.

Claim 8

In a phase-locked loop having a control signal fed back to a voltage controlled oscillator for tracking a carrier signal applied to said loop in an angle modulated communications system having said carrier signal modulated by at least two intelligence signal modulated subcarriers, a quadrature channel added to said phase-locked loop, comprising: means for multiplying said carrier signal by the output signal of said oscillator to produce a carrier product signal; means for forming a power estimate signal representing an estimate of the power of said two intelligence modulated subcarriers as the combined product of demodulated subcarriers and demodulated intelligence signals, said estimate forming means including means for aligning the phases of demodulated subcarriers and demodulated intelligence signals; means for delaying said carrier product signal by a period sufficient to align said carrier product signal with said power estimate signal; means for multiplying said delayed carrier product signal by said power estimate signal to produce a final product signal; means for filtering said final product signal to produce a d-c signal proportional to the power of said modulated subcarriers; and means for adding said d-c signal to said control signal fed back to said oscillator.

Claim 9

The combination of claim 5 wherein said means for forming said power estimate signal comprises: means for separately demodulating said two intelligence modulated subcarriers to obtain an estimate of said two subcarriers modulated on said carrier; means for separately demodulating said two subcarriers to obtain an estimate of said intelligence signals modulated on said two subcarriers; means for multiplying the estimate of each subcarrier by the estimate of its intelligence signal to obtain first and second products; first delay means for delaying said first product by a period equal to the intelligence rate of its intelligence signal; second delay means for delaying said second product by a period equal to the intelligence rate of its intelligence signal; and means for multiplying the output signals of said first delay means and said second delay means.