Patent ID: 8331519

Claim:
A frequency detector comprising: an error measurement unit that measures a time interval between zero-crossing points of an input signal that is modulated to provide a measured time interval; an error conversion unit that quantizes the measured time interval using one of modulation time intervals to provide a quantized time interval; and an error calculation unit that calculates a frequency error based upon a difference between the measured time interval and the quantized time interval to provide a calculated frequency error, wherein the error measurement unit comprises: a sampling unit that generates a first absolute value and a second absolute value respectively corresponding to the input signal and a delayed input signal at the sampling time points before and after a j-th zero-crossing point, where “j” is a natural number over 2; a first linear interpolation unit that generates a first interpolation value based upon the first absolute value and the second absolute value; a zero-crossing point detection unit that detects a zero-crossing point of each of the input signal and the delayed input signal and that measures the number of samplings between the j-th zero-crossing point and i-th zero-crossing point, “i” being a natural number greater than j, to provide a measured sampling number; and a second linear interpolation unit that generates an interpolation value difference based upon the first interpolation value and a second interpolation value generated at the i-th zero-crossing point, and that generates the measured time interval based upon the measured sampling number and the interpolation value difference.