Research On Key Technology And System Of Millimeter Wave FMCW Radar For Detection Of Targets On Road Surface

With the rapid development of electronics and information technology,the application of millimeter wave frequency modulated continuous wave(FMCW)radar has penetrated into many aspects of military and civil fields.In order to improve the detecting range,detection precision,imaging resolution and anti-jamming capability of FMCW radar,the research of key technologies such as millimeter wave wide-band high linearity sweep source,wide-band high power source,high gain narrow beam antenna,beam scanning technology,broadband low noise receiving technology have been paid much attention in recent years.With the goal of achieving an E-band FMCW radar for detection of targets on road surface,an overall scheme of RF front-end and antenna have been worked out and designed.Key techniques for E-band broadband high efficiency power combining have been studied.Design and optimization techniques of W-band frequency scanning waveguide slot array antenna and W-band high gain narrow beam reflector antenna are proposed.On this basis,the key components of the broadband power-combined amplifier and the high gain reflector antenna are developed.Then,the experimental research work on a prototype of the system has been carried out.The main achievements of this dissertation are as follows:1?An overall technology scheme is proposed for the RF front-end and antenna of an E-band FMCW radar for detection of targets on road surface.Based on SPM(small-perturbation model),the influence of road roughness,grazing incidence angle and frequency on road backscattering coefficient is systematically analyzed.The design principle of the overall index of the RF front-end and antenna for the on-road-target detection radar is established.According to this principle,the key parameters such as transmitting power,gain of antenna,range resolution,cross range resolution and real-time performance are analysis and demonstrated.Based on that,the analysis and design of the overall technical scheme of the RF front-end and antenna are completed.2?Based on the theory of traveling wave power combining,a compact E-band broadband traveling-wave power-combined amplifier with low loss waveguide-microstrip probe coupling structure and waveguide E-T power divider/combiner is proposed.The variation of the amplitude and phase characteristics of the power divider/combiner with the key circuit and the structure size is studied by using full wave simulation technology.The mechanism of parasitic modes coupling in a shielded microstrip line and the cavity resonance in the millimeter wave broadband circuit are analyzed in depth.The design criteria for broadband millimeter wave shielding cavity and the method to suppressing the parasitic resonance are proposed.A broadband power-combined amplifier module at E-band is designed and machined.The measured output saturated power is higher than 24 dBm in the frequency band of 71 to 80 GHz,the maximum power is 25.5dBm.The estimated active power combining efficiency is great than 77%,the maximum power combining efficiency is 85%.In order to realize the driving amplifier required for the E-band solid-state frequency doubling source and to meet the needs of the system test,a full Ka-Band high gain power-combined amplifier based on waveguide-microstrip probe-array has been fabricated and tested.The measured continuous wave saturated output power of the amplifier module is higher than 30.5dBm over the entire Ka-band and the small signal gain is greater than 40 dB.Power combining efficiency is within the range of 84% to 92%.3?To solve the problem of the high processing difficulty,high cost and the difficulty of guaranteeing performance consistency of W-band slotted-waveguide antennas,an improved method for extracting the conductance function of the slot is proposed,which effectively simplifying the process complexity.In this method,the waveguide wall thickness and the width of slots are set as constraint conditions and the depth of slots are altered in a step manner.Based on this method,a 76 elements waveguide slot array antenna based on WR10 standard rectangular waveguide is developed,which is used as a feed antenna for the on-road-target detection radar.The variation of antenna beam direction with frequency makes it possible for radar to scan in the vertical plane.The fabricated slotted-waveguide antenna has been tested by a Compact Range(CR)measurement system in an anechoic chamber.Measured gain of the slotted waveguide antenna is higher than 23.5dBi for a frequency coverage of 75 to 79 GHz,while the-3dB beam width is 1.2 degree and the side lobe level lower than-20 dB in E-plane.The-3dB beam scanning range in E-plane is 5.5° when the frequency sweeps from 75 to 79 GHz.4?A fast and efficient design method of electronically large size elliptic cylindrical reflector antenna with a Taylor distribution line source as the feed is proposed,which reduces the workload of simulation and the design periods of the traditional design method.The initial size of the reflector antenna,which can form both a narrower focal spot width in the near field and a higher directivity in the far field,is obtained by theoretic calculation of the half intensity focal spot width at the far focus in H-plane and the optimum aperture utilization of the reflector antenna.Then,with the goal of achieving the best antenna efficiency,the final processing dimension is obtained by simulation and optimization with the help of FEKO.The target detection function of the radar system is used to measure the half intensity focal spot width in H-plane near the far focus of the reflector antenna.At the same time,the radiation characteristics in H-plane of the far field of the reflector antenna are tested by a CR measurement system in an anechoic chamber.The measured gain of the reflector antenna is higher than 44 dBi,while the-3dB beam width in H-plane is 0.4° and the half intensity focal spot width near the far focus in H-plane is 0.37° to 0.4°.This reflector antenna is suitable for the target detection radar which has high requirements for the cross range resolution in the middle and long distance.5?Designing and adjustment of the RF transceiver front-end module have been fullfiled,and the integration of antenna system has been carried out.The experimental research of the E-band FMCW on-road-target detection radar has been done.According to the requirements of the RF front-end specification,the detailed analysis and design of the RF front-end is completed,with the electrical performance parameters of various source devices are fully considered.The effect of detection distance on the amplitude of beat signal after dechirp is eliminated by using the roll-off characteristic of the two order active high pass filter.The key indexes of RF front-end,such as transmitting power,receiving noise coefficient and receiving dynamic range,are investigated in the experiment.On this basis,a set of experimental verification system for on-road-target radar has been established,and the preliminary experimental test was carried out in the laboratory corridor environment.The experimental results show that the radar can effectively detect metal wrenches,cans,shells,tires,cartons,bubbles and other foreign samples in the test scenario.The detection accuracy of the target distance is 0.1m and the range resolution is 0.11 m,achieving the desired detection effect.