Research On The Generation Technology Of Linearly Frequency Modulation Signal In Microwave Photonic Radar

Radar technology is widely used in the military field and daily life.Modern radar systems need to have a longer detection range and higher resolution.The LFM signals have received more and more attention as commonly used transmit signals in pulse compression radar systems.The high-quality LFM signals with large TBWP can be generated by microwave photonic technology.In this paper,the technology of LFM signal generation is studied based on microwave photonics.The main contents of the work are as follows:(1)On the basis of analyzing the method to generate dual-chirp signal using MZM,a scheme to generate dual-chirp signal using DPMZM is proposed.The bandwidth and carrier frequency of the up-chirped and down-chirped signal are twice that of the modulated signal,and the overall bandwidth becomes four times.Simulation results show that dual-chirp signals with a carrier frequency of 60 GHz,bandwidth of 12 GHz and 20 GHz,TBWP of 120 and 200,and pulse compression ratio of 166.67 and 161.3 are generated respectively.(2)Based on the research of frequency doubling in microwave photonics,a scheme of large bandwidth LFM signal generation and de-chirp is proposed.The LFM signal is generated by using DPMZM and RPML.The center frequency of the signal becomes eight times,and the de-chirp is completed by a phase modulation at the receiving end.The results show that a LFM signal with center frequency of 80 GHz,bandwidth of 32GHz,TBWP of 320,and pulse compression ratio of 284.01 can be generated.The bandwidth,chirp rate,and TBWP of the LFM signal can be tuned by changing the number of cycles and parabolic modulation signal.In addition,it is analyzed that the system is affected by the noise of modulators and amplifiers.At the receiving end,the de-chirp process of echo signals with different delays is simulated.The delays are 1.0?s,0.9?s,0.7?s,0.5?s,0.3?s,0.1?s respectively.After de-chirping,the signals of 25.0GHz,23.0GHz,17.8GHz,13.0GHz,7.60GHz and2.50GHz are obtained respectively.The detection distances are 150m,135m,105m,75m,45m and 15m respectively.