| Recently,with the demand of continuous growing driving safety and automatic drive,the advanced driver assistance systems(ADASs)with the active safety technology have been developing fast.As a key sensor in the ADAS,the millimeter-wave automotive radars have broad application prospects.Antenna arrays for millimeter-wave automotive radar applications are investigated in this work.The main works of the thesis are as follows.First,based on the patch element width tapering method,a 12-element microstrip series-fed linear antenna array is design.Then using the Differential Evolution Algorithm(DEA),together with electromagnetic full wave simulation software HFSS,the sidelobe level(SLL)of the linear antenna array at center frequency of 76.5 GHz is optimized to-22.8 dB,under the constraint of 3-dB beamwidth and the mean beam tilt angle.Next,a Chebyshev tapered microstrip 1 to 8 power divider is designed to consititute an 8 × 12 microstrip series-fed planar array together with the optimized linear array.Finally,a Microstrip-Finline-WR12 transition and two metal waveguide structures which are suitable for thin substrates are designed to measure the antenna array.The measured results show that the gain and the SLL in the E plane at 76.5 GHz of the linear array are 14.6dBi and-20.1 dB,respectively.And the gain at 76.5 GHz of the planar array is 21.3 dBi,the SLL in the E plane and in the H plane at 76.5 GHz are-17.5 dB and-14.6 dB,respectively.Next,a 16-element center-fed substrate integrated waveguide(SIW)slot antenna array operates in the band of 77?81 GHz is designed.By using machine learning techniques,a surrogate model is built.By combining the DEA with the HFSS,the maximum SLL in the H plane in the band of 77?81 GHz is optimized to-19.6 dB.The measured results show that the gain at 79 GHz is 10.4 dBi,and the maximum SLL in the H plane is-12 dB at 81 GHz.Moreover,a novel wideband SIW cavity-backed slot antenna element which operates in the band of 75?82GHz is proposed.The antenna element consists of two L-shaped slot pairs.The simulated element gain is 10.9 dBi.After analyzing the negative effect of regular substrate bonding layer on the gain and radiation pattern of slot coupled antenna array,an antenna array is built.By adjusting the positions of metallic via holes and metallic blind holes,8 SIW isolation cavities with one side removed in the bonding layer are formed,which remarkably reduce the negative effect on radiation pattern and gain caused by electromagnetic energy leaks through the bonding layer.The measured results show that the gain of the antenna array at 79 GHz is 16 dBi and the gain fluctuation is less than 1 dB in the band of 75?82 GHz. |
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