High Precision Phase Measurement Using Reduced Sine and Cosine Tables

, 4 b s t r a c t : In conventional techniques [4-61 the phase angle between two signals of same frequency is computed by converting the signals into two square waves and then measuring the time difference between the zero crossing points of the square waves. In some other techniques the phase is computed by measuring the time difference between the pulse centers of the two square waves [l-31. However, all these techniques introduce error in phase measurement when the input signals are distorted by harmonics. A high precision phase measurement technique, which can accurately determine the phase even when the signals are distorted by harmonics, is presented in [7]. This paper proposes a microprocessor-based hardware implementation of the high precision phase measurement technique presented in [7]. T h e hardware implementation requires two reduced tables: a sine table and a cosine table. If each table has i(i+5)/2 entries then the phase could be accurately determine even if the signals are distorted by any number of harmonics in the range 2nd through ith h a r m o n i c s .