Research On RF Front-end Circuit Of Five-channel Air Detection Rada

In recent years,with the diversified needs of target detection scenarios,linear frequency modulated continuous wave(LFMCW)radars have become more and more popular by scholars due to its low power consumption,small size,high range resolution,no range blind zone,and all-weather work.Low-altitude and high-speed target detection is one of the popular application directions.Aiming at the detection of air targets with high maneuverability and short distances,this paper designs an X-band LFMCW radar for speed,range and angle measurement,focusing on the radio frequency front-end circuit.The radial filtering power divider is designed for the integration of the array unit,and the decoupling structure is designed for the isolation of the transceiver antenna.The main contents of this paper are as follows:1.According to the principle of LFMCW target detection and the requirements of detection in a large angle range,a uniform circular array layout of the transmitting and receiving antennas is proposed,and the radar parameters and system frame structure are further designed.2.Focus on the design of radial filtering power divider.Aiming at the filtering requirements of the local oscillator leakage and spurious signals of the radar in this paper,a new type of cascaded quadruplt structure with dual microstrip resonators added to the coupling path of the substrate integrated waveguide(SIW)cavity is proposed.This structure can create two adjustable transmission zero points to achieve sharp frequency selection performance.Finally,the single-layer and two-layer SIW radial filtering power dividers were designed respectively to verify the feasibility of the design method.3.Aiming at the problem of LFMCW transceiver isolation,based on the design of the patch antenna unit,a method to reduce the coupling of the transceiver antenna by using a multi-step choke groove structure and a multi-step nail bed structure is proposed.Explain the principle of improving the isolation and design the real object for measurement.The measurement results show that the proposed structure can increase the isolation by 30 d B and 24 d B respectively.4.The design of the LFMCW radar active circuit module was completed,and the whole system was assembled and debugged.The actual target detection experiment in the field has been completed.The detection range of the radar system in this paper is 20 m-200 m,the detection angle range is 360°,the pitch angle is ±40°,and the speed measurement error is less than 0.3 m/s.It verifies the feasibility of the proposed speed and distance measurement scheme in a large angle range.