Abstract: This paper presents a new phase in terferometer system combining hardware and software technology to solve the problem. AD8302 is used to measure the phase difference directly instead of the down converter, and to export the equivalent voltage signal of the phase difference. After the equivalent voltage signal is sampled, the Kalman Filter is used to optimize the Voltage signa1. Finally, the voltage signal is translated into the phase difference communication which can be used to calculate the location of the target. The calculation result shows that the phase difference measurement error reduces to only about 1／10 after using the Kalman filter.