Measuring Radar Microwave Frequency Instantaneously With Photonic Technology

In modern warfare, the radar plays an important role in the field of information access and precise navigation, and how to get access to radar parameters of the microwave carrier frequency instantaneously launched by the enemies is the key to affecting the result of the war situation in the electronic warfare. Traditional frequency measurement receiver can provide a measurement range of 0.5-18GHz with electronics methods(sensitivity no higher than -50dBm). Furthermore, the instantaneous frequency measurement system is complex, bulky, expensive and susceptible to electromagnetic interference. Recently, millimeterwave radar signal(0.5-40GHz) has been used in electronic warfare. Due to the complex electromagnetic environment, it is diffcult to achieve such a large bandwidth with traditional detection methods, and the traditional methods of the Instantaneous frequency measurement are facing challenges severely to meet the need of Modern electronic warfare. Microwave photonic technology can upgrade and improve the performance of the instantaneous frequency receiver, providing an wideband, low loss, anti-interference, small and portable solution.It is necessary to modulate the unknown microwave signal to optical carrier wave in order to measure microwave signal frequency instantaneously with microwave photonic technology, and modulated optical carrier going through a certain optical-fiber structure,an amplitude comparison function only related to microwave signal frequency could be obtained, so that microwave signal frequency can be worked out. With two light source generating optical carrier, the modulated carrier signal is processed by microwave photonic filter, completing instantaneous frequency measurement, but it is complex, high cost and a small range of bandwidth. It is simple to employ single source and commercial optical fiber Mach-Zehnder interferometer structure to achieve instantaneous frequency measurement with the use of the principle of light interference, but the output of the Mach-Zehnder interferometer are susceptible to interfer to external environmental conditions, resulting in considerable error, so it is diffcult to ensure the accuracy of the frequency measurement result. This paper introduces a new program, and still uses a single light source and fiber Mach-Zehnder structure, but it is necessary to choose broadband light source and design the optical fiber Mach-Zehnder structure reasonablely, striving to avoid the modulated optical carrier signal interfering. So the external environment influence to the result of the frequency measurement can be reduced, meanwhile a large range of measurement bandwidth is obtained. The simulation and analysis verify the feasibility and Effectiveness of the method.