Range And Velocity Measurement Based On Photonic-assisted Frequency Modulated Signal

For the next-generation of radar,remote sensing,target recognition and imaging,transmitting signals with ever-increasing bandwidth and large time duration are highly required to acquire high resolution and detailed information of interest.For conventional electrical radars,however,both analog and digital methods are facing the bandwidth bottleneck.Based on the advantages of microwave photonic technology,such as ultra-wide bandwidth,low transmission loss,compact size,and strong immunity to electromagnetic interference,a range and velocity measurement scheme based on frequency-modulated(FM)microwave photonic signal is studied,to achieve a high resolution and to improve the bandwidth range.In this thesis,the background,significance and purpose of the selected topic are first introduced.Brief introductions are given on the research status,showing the advantages of microwave photonic technology in radar systems.In the meanwhile,deep illustrations on FM signal as well as its application in range and velocity measurement are provided in Chapter two.Then,the range-Doppler coupling problem of the single chirped signal is analyzed,explaining the advantage of the V-shaped FM signal in the range and velocity measurement.Secondly,a method of broadband FM microwave signal generation based on microwave photonic is studied,and experiments show that the scheme can generate not only tunable high-frequency broadband FM microwave signal,but also broadband FM optical signal by extending the link.A range and velocity measurement scheme based on FM microwave photonic signal is designed based on the signal generation method above,including mainly the generation of the transmitting signal and the processing of the receiving signal.A high-frequency electrical signal is generated in the transmitter using frequency doubling enabled by photonics,which improves the range resolution.Also,a high resolution is improved again by using cascaded modulator in the receiver during the range and velocity measurement.Then,the feasibility of the proposed scheme is verified by software simulation and experiments.Simulation results show that the scheme can realize the function of range and velocity measurement,and experimental results indicate an absolute error less than 3 mm,a range resolution up to 3.75 cm and a detection distance of 3.5 m,when the transmitting signal has a bandwidth of 2 GHz and a pulse width of 10 ?s along the ascending and descending sides respectively.In addition,the performance of the proposed scheme in terms of low power level is analyzed experimentally.The range and velocity measurement scheme based on FM microwave photonic signal studied in this thesis can improve the measurement resolution,and has significant bandwidth advantages in the generation of transmitting signal and the processing of receiving signal,which is significant in the fields of radar and detection to improve the performance of range and velocity measurement.