Errors of In-Phase and Quadrature demodulation method created by low-pass filter

This article explores phase errors created by low-pass filter in interferometric signals which are processed by In-Phase and Quadrature demodulation algorithm (IQ-demodulation). These errors were calculated using the analytical method and were compared with mathematical modeling, which uses pre-calculated parameters: phase, sampling period, infinitesimal parameters. In this paper, we show that phase errors calculated with analytical method clearly correlate with mathematical modeling errors. This work made it possible to calculate corrections to the demodulated phase, which, in turn, made it possible to refine the phase calculation step in IQ demodulation algorithm using the arctangent function. The resulting formulas describing the correction to the demodulated phase will increase the accuracy of the quadrature method, which is used to process signals from interferometric devices of various types, such as: reflectometers, geophysical seismic systems, interferometric radiometry, etc.