Photonic-assisted multi-functional system for simultaneous distance, velocity and frequency measurement

Abstract

A photonic-assisted multi-functional system that can implement simultaneous distance, velocity and frequency measurement is proposed and experimentally demonstrated. The distance and the radial velocity of a moving target are measured by transmitting a complementarily (V-shaped) linear-frequency-modulated microwave waveform, and by mixing the reflected microwave waveform with the transmitted microwave waveform, two de-chirped waveforms with different carrier frequencies are generated. The distance and the radial velocity are measured by analyzing the de-chirped microwave waveforms. Frequency measurement can also be performed by the system which is done by modulating a received unknown signal on an optical carrier which is mixed with a frequency-sweeping light. By passing the mixed signal through an electrical bandpass filter, short electrical pulses are generated. By measuring the time delay difference between adjacent pulses, the frequency of the unknown signal is measured. The operation of the proposed system is evaluated experimentally. The results show that the distance and velocity can be measured with mean absolute errors of 2.95 cm and 6.09 cm/s, respectively, with a range resolution better than 5.5 cm. The frequency measurement function with the capability of implementing single-tone, multi-tone and broadband signals is verified for an input signal with a frequency ranging from 1 to 20 GHz. The mean absolute error of the frequency measurement is 34.22 MHz.