| 摘要 |
A timing error extractor (166) determines the phase angle between an input signal and a sampling clock by computing arctan(v/u)=arctan(alog(log(v)-log(u)), where (v) and (u) are the respective quadrature amplitudes of the input signal and sampling clock. The log function values are stored in a first lookup table (180) that is time-shared by a switching function (182) to provide both log(v) and log(u) values. A storage element (184) holds the log(u) value while the switching function routes magnitude (v) to the first lookup table. The resulting log(v) value and the stored log(u) are combined in a subtraction function (186) that generates log(v)-log(u), which result addresses a second lookup table (188) that returns the addressed arctan(alog(log(v)-log(u)) value. This phase estimating approach is advantageous because it is gain insensitive, does not include a costly and time-consuming divide operation, and requires a relatively small lookup table.
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