| With the continuous improvement of the economy,China’s automobile industry and transportation industry have made rapid progress.The number of motor vehicles is increasing year by year.While automobiles bring convenience to people,they also cause a series of traffic problems.In order to ensure the safety of driving and improve the intelligence of driving,as early as 60 s and 70 s twentieth Century,countries began to explore the automobile ranging system preliminarily.Until twenty-first Century,automobile ranging technology entered the stage of full and rapid development.In recent years,the advanced driving assistance system(ADAS)has become a hot topic in the industry.It uses various sensors installed on the vehicle to collect various data inside and outside the vehicle,and feedback the specific information of obstacles,so as to control the vehicle and avoid the risks.Traditional ultrasonic,infrared and other radar can detect the distance very close,and are easily restricted by weather and night conditions.Microwave radar is a new ADAS sensor,which is hardly limited by weather and nighttime.Its detection distance is far away and the precision is high.It occupies an absolute advantage.The research on microwave automobile ranging radar started late in China.At present,the domestic research focuses on the 24 GHz band,which is mainly applied to reversing car collision avoidance,blind spot monitoring and lane changing assistance.This topic researched and designed antenna part and transceiver module of a24 GHz automotive ranging system,it can transmit and receive 24 GHz signal correctly.And it has small volume,high integration and easy installation.The antenna part consists of a transmission antenna and two receiving antennas,all of which are microstrip array antennas,and adopts the two comprehensive methods of exponential distribution and Chebyshev to design the feed network.It has the performance of narrow beam,low side lobe and high gain.The transceiver module is designed based on RF transceiver chip BGT24ATR12 and phase-locked loop chip ADF4158.ADF4158 generates control voltage and controls VCO in BGT24ATR12 to generate linear frequency modulation signal.The signal is sent out by the transmitting antenna.The echo is generated after the obstacle is encountered.When the echo signal is received by receiving antenna,it is mixed with the signal directly transmitted from thetransmitter to get the IF signal containing the distance information.The topic focuses on the front-end antenna.The main work of this project is as follows:1、The research on the theoretical basis of FMCW ranging system.This paper briefly introduces the research history,development situation and trend of automotive ranging system at home and abroad,compares the detection mode and radar system of the commonly used ranging system,and expounds the working principle of the FMCW range finder system.And the main structure of it is described in this paper.2、Design of detecting antenna.For the 24 GHz vehicle ranging system,this paper designs two 2 × 10 transmission array antennas and two 4 × 10 receiving antenna groups(including two receiving antennas).All of them are in series parallel connection of the feed network structure,and use the two methods of exponential distribution and Chebyshev synthesis to reduce the sidelobe level.The narrow beam,low side lobe and high gain are finally realized.The simulation optimization is completed and then processed.Finally,the performance of the antenna is tested,and results are basically consistent with the simulation results.3、Design of transceiver module.The transceiver module takes BGT24ATR12 RF transceiver chip as the main chip,and adds other devices such as phase-locked loop and CPLD chip.The module realizes the sending,receiving and preliminary processing of the signal,and obtains the IF signal.Finally,the hardware is made and tested on the basis of the schematic diagram.4、Hardware overall test.By using DC power,signal source,spectrum analyzer and other equipment,launch test and receiving test are carried out respectively.The test results show,the antenna part and transceiver module can realize long distance24 GHz frequency signal transmitting and receiving,and can produce intermediate frequency signal with distance information,the design is correct and effective. |
