Simultaneous Radar Detection and Frequency Measurement by Broadband Microwave Photonic Processing

Incorporating radar detection and frequency measurement functions within a single system is highly desirable in modern RF applications. In this article, a microwave photonic system is proposed and demonstrated to simultaneously realize broadband radar detection and frequency measurement. By sharing a light with +/- 2nd-order linear frequency-modulated (LFM) sidebands in a polarization-division-multiplexing manner, radar detection and frequency measurement functions can be realized simultaneously. In the transmitter, the shared light is used to generate a radar signal that has a quadrupled bandwidth compared with the input electrical LFM signal. In the receiver, the shared light is applied as the reference to perform photonic de-chirping of the radar echo and to scan the frequency of the signal under test (SUT) along two orthogonal polarization directions. In the experiment, a 4.5-6.5 GHz LFM signal is used to generate the shared light source, based on which radar detection (bandwidth: 18-26 GHz) with a range resolution as high as 2.06 cm, and frequency measurement (measurement range: 28-36 GHz) with a scanning rate of 0.8 GHz/mu s and a resolution of 37.6 MHz are achieved. In addition, the reconfigurablilty of the frequency measurement range, and its capability for measuring the multi-tone and wideband signals are also demonstrated.