Simultaneous Echo Power and Doppler Frequency Measurement System Based on Microwave Photonics Technology

A Doppler shift measurement system based on four-wave mixing effect in a highly nonlinear fiber is demonstrated practically. The system exhibits two low-frequency voltages, which are functions of the Doppler shift, and therefore, low-cost low-frequency photodetectors can be employed in the system. No sophisticated electrical instrument is required to perform the measurement. The scheme is able to simultaneously and independently measure the Doppler frequency of a radar echo and its power level with carrier frequency up to 40 GHz. The system is suitable to be employed in any microwave photonics (MWP) radar system with broad frequency agility characteristics or the other MWP systems operating based on frequency hopping technique.