| As an effective active safety defense device,millimeter-wave vehicle anti-collision radar has gradually become a research hotspot of major scientific research institutes and automobile manufacturers.Among them,the 77GHz radar device is small in size,light in weight,and highly adaptable to the environment,and it can achieve long-distance detection and high spatial resolution at the same time,whose advantages make it the mainstream of anti-collision radars in the future.In the automotive anti-collision radar system,the microstrip patch antenna has become the main form used today because of its high gain,miniaturization,and ease of integration with planar circuits.The mid-range distance vehicle anti-collision radar concentrates on the range of targets in front,and filtering the air and ground clutter by reducing the side lobes,which becomes the focus of current research.Today's market-oriented millimeter-wave anti-collision radars adopt the form of vertical polarization.In the case of opposite traffic,there will be strong electromagnetic interference between the radar devices with the same vertical polarization,and the proposed microstrip series-feed antenna of 45-degree linear polarization form provides a new idea for the anti-jamming capability design of future front-end anti-collision radar.This paper firstly has introduced the working principles and basic parameters of the microstrip antenna,and also the form and idea of the two arrays,namely the line array and the area array.The analysis of the advantages and disadvantages of the series and parallel feeds lays the foundation for the design of the feed network.Secondly,a group of W-band 77 GHz vertically polarized antenna arrays were proposed.The feed mode of series-fed linear array is cascaded and the efficiency of the antenna is high.The side lobe of the antenna is reduced through antenna synthesis.The power divider with first order and ten ways achieves the power division ratio of 4.5 times instead of the quarter wavelength transmission lines by the T-shaped structure junction,which has achieved a low side lobe in the horizontal orientation of the long-range emission array.In order to verify the performance of the antenna,a broadband ridge-finline and microstrip converter was designed.The processed antenna was tested by the standard WR10 waveguide.The test results show that the antenna bandwidth exceeded 1.4 GHz,but the resonance point occurred to varying degrees at low frequencies.The simulated sidelobe level is lower than-20dB,and the measured sidelobe level is lower than-17dB.The half-power beam width is basically the same as the design result.Finally,a novel set of W-band 77GHz 45-degree linearly polarized microstrips were proposed.The single-row series-fed antenna array with sidelobe suppression of 25dB was designed by the amplitude-weighted,combined with reflection-canceling unit.By adding welted rectangular slots,the cross-polarization ratio of the main beam is improved by a maximum of 20 dB,and the cross polarization level in the normal direction is-23 dB.A first-order ten-way power splitter was used to examine the sidelobe suppression of the antenna and the improvement of cross-polarization based on the new patch unit in the area array design.In order to further reduce the cross-polarization level in the normal direction,a linear array of center-feed was proposed,and the cross polarization level in the normal direction is-33 dB. |
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