Optimal Design Of Millimeter Wave Automotive Radar Antenna System

Today,Millimeter-wave automotive radar is widely used as an important sensor in safe driving assistance system.Automotive sensors typically use frequency modulated constant wave(FMCW)as working mode,and calculate the target vehicle's speed,distance and angle by processing the the down converted signal.Automotive radar antennas are the most critical part of the radar's transmitting-receiving electromagnetic wave link.In order to have long-range detection capabilities for automotive sensors installed in complex and narrow environments,automotive radar antenna system designs often require miniaturization,high gain,low Sidelobe and high isolation,which put forward high requirements and challenges.Therefore,this paper focuses on practical problems in engineering applications:1.How to realize the miniaturization design of millimeter-wave automotive radar antenna systems;2.How to improve the problem of reducing the detection distance of automotive radar due to the coupling between transmitting and receiving antennas;3.How to improve the accuracy of radar sensors angle measurement.The main contents include the following parts:Firstly,by studying the linear array antennas synthesis method,two antennas working in the 24 to 24.25 GHz with the gain on less than 14dB and the sidelobe level less than-18dB are designed.One of the antennas uses a comb antenna design,which has a shorter feed length.The designed one-transmitting-two-receiving miniaturized radar antenna has an aperture of only 50mm×45mm.Secondly,by researching two decouple methods of the electromagnetic band gap periodic structure and the dummy antenna,the isolation between transmitting and receiving antenna of automotive radar transceiver antenna is improved greater than 45dB.The electrical band gap periodic unit uses the Jerusalem cross slot structure,and the structure's band gap characteristics are analyzed by the suspended microstrip method.The dummy antenna adopts the same shape structure as the transmitting and receiving antenna.Analyze the mutual coupling relationship between the transmitting and receiving antennas through the microwave network method,and use the optimization algorithm to calculate the optimal placement position and terminal load of the dummy antenna.Furthermore,by introducing single-baseline and dual-baseline phase interferometer angle measurement methods and digital beamforming(DBF)method,the high-precision angle measurement methods of millimeter-wave automotive radar are researched.The dual-baseline phase interferometer angle measurement method can resolve the phase ambiguity in the single-baseline method,and improve the accuracy by increasing the length of the baseline.Digital beamforming method generates digital beams with different directions through digital signal processing,and uses a three-beam parabolic method to compare the amplitudes of the target echo signals to obtain the angle.Compared with the interferometer angle measurement method,digital beamforming method has higher measurement accuracy.Finally,as an extended research,a multiple field-of-view pattern antenna synthesis method based on hybrid algorithm of genetic algorithm and aggressive space mapping is proposed for application of 77GHz vehicle anti-collision radar.The multiple field-of-view pattern antenna can realize the requirement that a single-channel transmitting antenna has different detection field-of-view angles according to different detection distances,and can lower hardware cost than the current method of combining multiple antennas.By designing a multi-field-of-view pattern array antenna as an example,the simulation calculation process of the propose method is introduced in detail to provide a reference for actual engineering design.