Research On Optical Broadband Radio Frequency Correlator

Microwave signal recognition is a critical technique in electronic warfare,which involves frequency measurement and chirp rate measurement.In the conventional microwave measurement based on electronic technology,due to the existence of electronic bottleneck,the working bandwidth is limited,and the response speed is generally slow in a large frequency range.In contrast,the photonic microwave signal measurement technology based on microwave photonics has significant advantages in anti-electromagnetic interference,instantaneous bandwidth and other aspects.In this paper,the main content of this thesis is the optical wideband RF correlator based on frequency shift loop structure.The frequency shift loop is used to realize the time-frequency mapping of discrete Fourier transform to achieve a higher resolution frequency measurement result of broadband microwave signal.In addition,by adjusting the frequency shift,the fractional Fourier transform can be realized,the pulse compression of LFM signal can be realized,and the chirp rate of LFM signal can be measured by using the same system.The experimental scheme has the advantages of higher frequency resolution,higher chirp rate measurement accuracy and larger working bandwidth.Main work of this paper is as follows:1.The research progress,basic concepts and basic structure of the dispersion Fourier transform are introduced,with emphasis on the principle of the fractional Fourier transform based on the frequency shift loop.The principle of microwave frequency measurement and chirp rate measurement based on this structure is deduced in detail.On this basis,combining with experiments,how to control the parameters of each instrument and device in the loop is analyzed in detail,so as to build a stable and high performance optical frequency shifting loop.2.A high-precision width frequency measurement method and data recovery algorithm based on optical frequency shift loop is proposed and verified.The simulation design of frequency measurement based on frequency shift loop is realized by writing software program on Matlab software platform,which ensures the feasibility of the theory.A reasonable frequency recovery algorithm is designed to keep the high accuracy of frequency measurement and widen the range of frequency measurement.The influence of the parameters of each device in the loop on the system performance is analyzed in detail.The experimental results show that the high precision frequency measurement results can be achieved under 80 k Hz within the bandwidth of 4GHz.3.A broadband chirp rate measurement method and pulse compression scheme based on optical frequency shift loop are proposed and verified.Under the existing experimental conditions,the chirp rate of the LFM signal in the measurable range is measured,and the measured results are obtained within 0.5 MHz/ ?s measurement error.The correctness and feasibility of the system scheme are verified by the detailed simulation analysis of the linear frequency modulation signal.This paper summarizes the error sources of chirp rate measurement of LFM signal and pulse compression scheme based on the principle of fractional Fourier transform based on frequency shift loop,and puts forward the corresponding improvement scheme.