Patent ID: 7558342

Claim:
A circuit for recovering a periodic signal from a data signal, the circuit comprising: a variable oscillator for producing an oscillating signal, said variable oscillator being effective for varying the frequency of said oscillating signal in response to a frequency control input; a logic transition detector circuit receiving said data signal and configured to produce a pulse signal in response to logic transitions in said data signal; a frequency detector circuit receiving said pulse signal and said oscillating signal and producing an intermediate-frequency-difference signal indicative of a frequency difference between said pulse signal and said oscillating signal; a pulse length limiter circuit receiving said intermediate-frequency-difference signal, said pulse length limiter circuit being effective for limiting a pulse length of said intermediate-frequency-difference signal to a multiple of the pulse length of said oscillating signal, and outputting the pulse length limited version of said intermediate-frequency-difference signal as a frequency-difference output; said frequency control input of said variable oscillator being responsive to said frequency-difference output, and said variable oscillator being further effective for modulating the frequency of said feedback-oscillator signal in response to said frequency-difference output.