Instantaneous Microwave Frequency Measurement Assisted By Microwave Photonic Technology

In modern electronic warfare, instantaneous frequency measurement (IFM) is a crucial technology. It is necessary to capture the electromagnetic radiation for detecting enemy, interfering enemy’s communication, confronting offensive and capturing enemy’s information. Instantaneous frequency measurement system can be used to quickly locate the unknown signal band, and identify the type and quantity of enemy’s electronic equipment, and other important information, which will help us take reasonable attack or replied measures. Because of electronic bottleneck, the traditional electronic frequency measuring mechanism can not meet the needs of future wars.Photonic technology is introduced to implement low loss, small size, light weight, wide bandwidth, electromagnetic interference immunity microwave signal processing systems which are difficult to achieve in the microwave system. Due to the widespread attention from foreign and domestic researchers, related research has become the current hot spots. However, microwave photonics frequency measurement technology still faces some challenges. Military applications have strict requirements on the performances such as response speed, cost and so on. Furthermore, the the influence of Microwave photonic link characteristics on the frequency measurement capacity, especially the sensitivity and dynamic range is also needed systematic analysis. These key issues have been studied. The main innovative research efforts are summarized as follows.1) In order to meet the requirement of short response speed, photonic-assisted approaches have been proposed and demonstrated experimentally. The proposed schemes are based on the frequency-to-power mapping with cascading Mach-Zehnder Interferometers and polarizers. This scheme shortens the response time to the magnitude of10picoseconds. The measurement errors as shown in experimental results can be kept in0.1GHz over a frequency range of0.1GHz-8.5GHz.2) In order to meet the requirement of low cost, a novel photonic approach based on the frequency-to-optical power mapping have been proposed and demonstrated. This scheme avoids the use of high-speed photodetector, which can greatly reduce the system cost. A Mach-Zehnder Interferometer is used as the comb filter. Different optical carriers corresponding to different filter curves, resulting in orthogonal frequency transmission response, which could be used to carry out the measurement of microwave frequency. The measurement errors as shown in experimental results can be kept in0.2GHz over a frequency range of6GHz-10GHz.3) The performance of links in photonic assissted frequency measurement is analysised. The relationships among measurement sensitivity, measurement error, the link gain, noise figure, and the nonlinear distortion are studied, revealing the best indicators and performance can be achieved using intrinsic simulation photonic link. Under normal circumstances, the sensitivity of intrinsic microwave photonic link is-42dBm when the measurement errors are kept in0.2GHz. This research is quite important for the further optimization of frequency measurement means.