| 摘要 |
PURPOSE:To prevent an error of phase difference detection near 0 deg. or 180 deg. by not measuring a direct phase difference between a reference signal and a signal to be measured but by giving a prescribed phase bias to the reference signal with respect to the signal to be measured and measuring the result. CONSTITUTION:As reference signal inputs being the reference of phase difference measurement, for kinds of reference signals (No.1 system) whose phase is retarded by 45, 135, 225 and 315 degrees respectively and four kinds of reference signals (No.2 system) whose phase is retarded respectively by 0, 90, 180 and 270 deg. by a reference signal generating circuit 1 are outputted. The reference signals of the No.1 system is subject to phase-comparison with the signal input to be measured by a pass comparator circuit 2 and a prescribed reference signal selection signal is outputted. The selection signal is fed to a reference signal selection circuit 3 and a subtraction circuit 5. The selection circuit 3 selects the reference signal of the No.2 system reference signal from the reference signal selection signal and the result is fed to a phase detection circuit 4, where the signal to be measured and the reference signal are subject to phase difference detection and the phase difference data is outputted.
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