Patent ID: 7860205

Claim:
An apparatus for synchronizing a local clock at a receiver with a local clock at a transmitter, where indications of transmitter clock signals are communicated to the receiver as timestamps, the apparatus comprising: a phase detector operable to compute an error signal indicative of differences between the timestamps and a local clock signal; a loop filter operable to estimate a frequency offset of the receiver clock with respect to the transmitter clock by weighted least-squares calculation, and thereby produce an estimate of the receiver frequency, the weighted least-squares calculation including calculating a first order finite difference function of a past frequency estimate and an offset value, the offset value based on first and second order finite difference equations; a control signal produced by scaling an estimated frequency by a factor dependent on a receiver oscillator characteristics; a digital oscillator operable to oscillate at a frequency based at least in-part on the control signal, and thereby produce a digital oscillator output signal; and a counter operable to receive the digital oscillator output signal and to count pulses in the digital oscillator output signal, and output the local clock signal.