Patent ID: 8868364

Claim:
A device for measuring power of an alternating current (AC) comprising: a frequency detector having a first oscillator to generate a local reference signal to detect a fundamental frequency of the AC and a controller to generate a control signal indicating the detected fundamental frequency of the AC; and a power analyzer to analyze power of the AC, the power analyzer comprising: a second oscillator, to receive the control signal from the frequency detector, to generate first and second substantially mutually orthogonal sinusoid signals at a programmable harmonic of the fundamental frequency; a first group of multipliers for mixing the first and second sinusoid signals with a current data signal and a voltage data signal of the AC respectively; a group of low-pass filters for respectively removing high frequency components from a multiplication product of the first group of multipliers; a second group of multipliers for respectively mixing the filtered multiplication products; and a plurality of adders each to sum together a pair of multiplication products of the second group of multipliers.