Design And Implementation Of Radio Frequency Front-End Of Frequency Modulated Continuous Wave Radar

With the continuous development of drone imaging technology at home and abroad,the demand for imaging radar is also increasing.This thesis integrates domestic and foreign UAV imaging radar technology,and proposes a Linear Frequency Modulated Continuous Wave(LFMCW)radar system based on the miniaturization,low power consumption and other characteristics.LFMCW radar is a radar that uses linear frequency modulated continuous wave signals to obtain distance and velocity information.It achieves high resolution by effectively increasing the signal bandwidth,and has no distance blind zone,high resolution,and is easy to integrate other devices.Therefore,it is widely used in UAV imaging radars.The main work of the thesis includes the following aspects:Based on the detailed analysis of the application and function of the UAV imaging radar,the working frequency band,radar system,antenna parameters,and transmission power of the LFMCW radar program are formulated.The effects of the leakage signal of the strong transmit signal on the isolation of the transceiver are eliminated through the three mixing frequency operations,the radio frequency cancellation function is realized,the overall framework of the radar system is determined,and the frequency domain response characteristic of the system frame is obtained using AWR VSS simulation.Its high practicality is verified.When designing the frequency synthesizer module,a linear frequency sweep circuit based on DDS and multiple phase-locked loops is designed on the basis of the effects of signal linearity,phase noise,spurious,etc.This circuit can greatly improve the phase noise and spurious of the frequency source.It can also makes the digital control to the sweep frequency system,it is easy to realize the high sweep frequency linearity and the sweep frequency slope adjustment.This thesis describes the leakage problem of the LFMCW radar's transmission signal in detail,gives a variety of ways to eliminate the leakage signal,introduces the RF cancellation function of the three-stage mixing module in this system,and designs a Dechirp band-pass filter which uses 7-order elliptic LC structure through AWR simulation.In the antenna design,a 2×8 microstrip slot-coupled antenna array was used to obtain the required index through HFSS simulation.The entire radar system layout,hardware system,installation and commissioning are completed.The availability of the implementation of the system designed herein is verified by a test system.