Calibration of 90° phase difference measured by digital sampling method

Digital sampling method is widely used in precision electromagnetic measurements based on DFT algorithms. The accuracy of phase difference measured by sampling method influences a lot to power, energy and so on. The active phase shifter is constructed to get stable 90° phase standard. To obtain the error of the phase shifter, two calibration steps are carried out in which a 1:-1 two-stage inductive voltage divider (IVD) is used. The calibration uncertainty for the 90° phase difference is 0.0006°. With the 90° phase standard, phase difference measured by a synchronous sampling digitizer using an improved DFT algorithm is calibrated.