| Millimeter-wave(mmWave)automotive radar has attracted much attention as a key sensor for active safety measure of vehicles and future driverless cars.As a key component in radar systems,the radiation performance of mmWave antennas plays an important role in mmWave automotive radars in terms of system performance,shape and size,and overall cost.Therefore,designing high-performance mmWave antennas that can meet the needs of the system is an important research topic.This research mainly studies the microstrip traveling-wave array antenna applied to 77GHz mmWave automotive radar,which mainly includes four parts:1.Firstly,the thesis investigates the development of automotive radars and automotive radar antennas at home and abroad,and analyzes the development trend of millimeter wave automotive radar antennas.And then,the related antenna theory is summarized,which lays a theoretical foundation for the subsequent antenna design.2.The design of the comb array antennas for 77GHz mmWave automotive radar is mainly studied,including standing-wave series-fed array antenna and conventional traveling-wave series-fed array antenna.Two kinds of array design methods are introduced in detail,including theoretical calculation,parameter extraction and sidelobe control.Finally,through comparative analysis,it is pointed out that the standing-wave array has a narrow bandwidth and cannot obtain the shaped beam pattern,while the conventional traveling-wave array has a wider bandwidth but cannot obtain the broadside pattern.3.Aiming at the shortcomings of the conventional traveling-wave series-fed array antenna,a novel comb antenna element with reflection-canceling structure is designed firstly.Based on the comb elements,an 18-elements traveling-wave linear array is constructed and measured.The results show that the array antenna can achieve the broadside radiation pattern.Besides,the |S11| is less than-15dB over the 76-77GHz frequency band,the sidelobe level(SLL)in the elevation plane is lower than-21dB,and the half power beamwidths(HPBW)in the azimuth plane is 70°.Finally,this array antenna is applied to an 8-channel Digital Beam Forming(DBF)radar system.It is found that the array antenna has two key characteristics required by a DBF radar system:One is wide beam,whose HPBW is greater than 100°,and the other is high isolation,whose isolation between channels is greater than 25.3dB.Compared with the conventional standing-wave array,the HPBW is increased by about 18° in the azimuth plane,and the isolation between adjacent arrays can be increased by 3dB,which shows its advantages in automotive radar applications4.Combined with the system requirements of 77GHz short-range(SRR)and long-range(LRR)dual-mode automotive radar,a 3T8R MIMO array based on a new traveling-wave comb array antenna was designed.The LRR includes 2 transmit(Tx)antennas,the SRR includes 1 Tx antenna,and the two modes time-sharing the eight receive(Rx)antennas.As the LRR has a longer detection range and a narrower antennabeamwidths,the 4x18 array is adopted.The HPBW of the LRR Tx antenna is 20° in the azimuth plane,and the SLL is lower than-21dB in the elevation plane,the antenna gain is greater than 20.7dBi.The Tx antenna for SRR and all Rx antennas adopt a novel 18-element traveling-wave comb array antenna.In the MIMO antenna system,the |S11| of each channel is less than-20dB,and the isolation of channels is greater than 25.3dB.The antenna pattern indicators of each channel meet the requirements of radar indicators,which makes the proposed antenna a good candidate for the 77GHz millimeter wave automotive radar. |
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