Research On The Radio Frequency Front-end System Of Land And Air Target Detection Radar Based On LFMCW

With the explosive development of the information age,the requirements of intelligent detection for radar system are higher and higher,including detection accuracy,detection range,detection environment,power consumption,volume and etc.For the detection of maneuverable aerial targets and ground targets with weak echo signal,a Ku band LFMCW radar front-end system is developed by designing a high-performance SIW filter and filtering power divider.The research works of this paper are as follows.1)By analysing the principle of LFMCW radar measuring range,velocity and angle,the system structure of LFMCW radar is designed according to the detection specifications.The design parameters of each circuit are calculated reasonably,and the basic scheme of LFMCW radar is determined.2)According to the requirements of LFMCW radar system for local oscillation,spurious suppression and miniaturization,a band-pass filter with two transmission zeros and a four-port filtering power divider based on SIW are developed.By introducing electric coupling with short grounded coplanar waveguide(GCPW)transmission line,two transmission zeros are achieved at the target position on each side of the filter passband.By analysis of the circuits of the filtering equal power divider and unequal power divider,the design process is summarized and the filtering power divider design examples with the power ratio of 1:2,1:16 And 1:1:1 are given.3)According to the design specifications of the system,modules of the transmitting link and two receiving links in the radar system are designed,including the circuit design of LFM source,local oscillator source and IF processing module.The component selection and working principle of mixer,amplifier and frequency multiplier are also introducted.The performance of each module is tested to verify its performance.4)The principle of difference-frequency ranging and sum-difference angle measurement is verified by the MATLAB signal processing on the test data of the system.The experimental results show that the transmitting chain with SIW filter and SIW filtering power divider can restrain the stray emission to 48dBc which improves the spectral purity of the transmission signal,the sensitivity of the receiver,and the detection performance.Finally,a set of high-precision LFMCW radar with 2W transmitting power is successfully developed.The range of detection is 30m?500m,and the range of pitch angle is-10°?20°.The size of the radar is(?)24cm×12cm,with stable performance,simple operation and easy productization.