Digital frequency-locked loop for use with staggered sampling systems
First Claim
1. A method for providing a sampling signal having a first frequency corresponding to a first period wherein said first frequency is maintained in substantially constant proportion to a second frequency of an input signal, said method comprising the steps of:
- (a) sampling said input signal at instants determined by said sampling signal to provide a plurality of data signals wherein each said data signal represents the magnitude of said input signal at the sampling instant;
(b) performing an approximation to the optimal mean square estimation analysis on said data values to minimize the sum of the squares of the errors between said data values and assumed values with respect to phase angle, amplitude and frequency to thereby provide a frequency deviation signal which is indicative of the frequency difference between said first and second frequencies; and
(c) modulating said first period in response to said frequency deviation signal such that said frequency deviation signal is minimized and, therefore, said first frequency is maintained in substantially constant proportion to said second frequency.
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Abstract
A digital frequency locked loop is disclosed for use with programmable signal processing apparatus wherein frequency locking is desired from staggered data samples. Sampling means are provided for sampling an input signal, at instants determined by the sampling signal, to provide N data signals from M cycles of the input signal wherein each data signal represents the magnitude of the input signal at the sampling instant. Signal processing means are provided for performing a unique approximation to the optimal mean square estimation analysis to provide a frequency deviation signal which is proportional to the difference in frequency between the sampling and input signals. The frequency deviation signal is used to modulate the period of the sampling signal such that the frequency of the sampling signal is maintained in constant proportion to the frequency of the input signal.
25 Citations
10 Claims
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1. A method for providing a sampling signal having a first frequency corresponding to a first period wherein said first frequency is maintained in substantially constant proportion to a second frequency of an input signal, said method comprising the steps of:
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(a) sampling said input signal at instants determined by said sampling signal to provide a plurality of data signals wherein each said data signal represents the magnitude of said input signal at the sampling instant; (b) performing an approximation to the optimal mean square estimation analysis on said data values to minimize the sum of the squares of the errors between said data values and assumed values with respect to phase angle, amplitude and frequency to thereby provide a frequency deviation signal which is indicative of the frequency difference between said first and second frequencies; and (c) modulating said first period in response to said frequency deviation signal such that said frequency deviation signal is minimized and, therefore, said first frequency is maintained in substantially constant proportion to said second frequency. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for providing a sampling signal having a first frequency corresponding to a first period wherein said first frequency is maintained in substantially constant proportion to a second frequency of an input signal, said apparatus comprising:
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(a) means for sampling said input signal at instants determined by said sampling signal to provide a plurality of data signals wherein each said data signal represents the magnitude of said input signal at the sampling instant; and (b) signal processing means for performing an approximation to the optimal mean square estimation analysis on said data values to minimize the sum of the squares of the errors between said data values and assumed values with respect to phase angle, amplitude and frequency to thereby provide a frequency deviation signal which is indicative of the frequency difference between said first and second frequencies, said signal processing means being further adapted to provide said sampling signal and to modulate said first period in response to said frequency deviation signal such that said frequency deviation signal is minimized and, therefore, said first frequency is maintained in substantially constant proportion to said second frequency. - View Dependent Claims (7, 8, 9, 10)
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Specification