| With the rapid development of the automotive industry and artificial intelligence technology,a safe and reliable driving experience is increasingly becoming an important criterion to measure the overall performance of a car.Millimeter-wave radar is widely used in driving assistance systems as a high-performance sensor with little environmental impact.The antenna,as the front-end part of the radar,is the key to whether the system can achieve longdistance and high-precision detection.In recent years,the grid antenna has received extensive attention from researchers due to its high gain,low profile,and low cross-polarization characteristics.In order to meet the performance requirements of millimeter wave automotive radar for antenna gain,size and bandwidth,this paper carried out an integrated antenna based on the grid array antenna for 79 GHz millimeter-wave automotive radar.The main contents of the paper include:1.First,the research on millimeter wave automotive radar antennas is summarized.Secondly,introducing the classification of automotive radars,focusing on the principle of FMCW radar range,speed,angle measurement and the principle of MIMO antenna to increase the antenna’s aperture through synthetic virtual array.Then compared the current mainstream manufacturers’ solutions to automotive radar transceiver chips,and chose CALTERAH CAL77A4T8 R as the transceiver chip for subsequent design references.Finally,the radiation principle of the grid antenna is explored,and the grid antenna is analyzed using the equivalent magnetic current method.The grid antenna E plane and H plane radiation pattern are obtained by calculating and fitting the contribution of the equivalent magnetic current of the radiating edge and the non-radiating edge to the antenna’s far field,which are basically consistent with the simulation results.2.A curving line wideband compact grid array antenna structure is proposed.By replacing the radiator of the grid antenna with an ellipse from the traditional linear shape,and bending the non-radiating edges,the size reduction and bandwidth expansion of the grid antenna are realized,the problems that grating lobes due to the large unit size and bandwidth cannot fully cover the working frequency band of 79 GHz millimeter wave automotive radar are solved.3.Based on the CALTERAH CAL77A4T8 R transceiver chip and the wideband compact grid array antenna structure proposed in this paper,a set of automotive radar antenna solutions are proposed,including the design of the low-loss interconnection structure between the chip and the antenna and the design of the antenna array.The antenna array includes 8×6 multiple field-of-view transmitting array antenna,3×6 transmitting array antenna loaded with parasitic elements,and 8×6 receiving array antenna,of which 8×6 receiving array can be combined with 3×6 transmitting array antenna to form 3-transmit and 8-receive MIMO array antenna.In the 8×6 multiple field-of-view array antenna design,based on the beamforming theory,a 1 to16 power division phase shift network is designed for feeding,so that a single-link-fed radar system can simultaneously conduct targets in three distance ranges without blind spot and reduces the demand for the number of chip links and the difficulty of signal processing.The3-transmit and 8-receive MIMO array uses the synthesized virtual array to expand the antenna aperture,which helps to improve the angular resolution of the radar,so that the radar has both azimuth and elevation detection functions.In the design of the MIMO array antenna,on the one hand,the beam width is expanded by placing parasitic elements on both sides of the transmitting antenna;on the other hand,by arranging the planar electromagnetic band gap structure between the receiving and transmitting arrays,the isolation between the transmit and receive arrays is improved. |
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