| In recent years,with the rapid development of artificial intelligence and autopilot technology,millimeter wave automotive radar as an important part of the automatic driving system,has gradually become a research hotspot in the field of industry and scientific research.In order to meet the performance requirements of millimeter-wave automotive radar system for antenna gain,bandwidth,sidelobe level and polarization characteristics,etc.,this paper studies 77 GHz automotive radar millimeter-wave antenna array based on low-temperature co-firing ceramics technology and substrate integrated waveguide technology.The specific contents are as follows:In order to meet the requirements of automotive radar antenna for high gain and low sidelobe level,a radiation structure of substrate integrated cavity with high-order mode resonance is proposed,the resonator operates in TM21111 mode.The influence of high order mode aperture surface field on radiation pattern is analyzed.In order to solve the problem of high order mode radiation pattern splitting,parasitic patch is added to the surface of the substrate integrated cavity to adjust the electromagnetic field of the cavity aperture surface.The field distribution achieves high gain normal radiation on the aperture surface of the high order mode;then,the T-type unequal power divider of the substrate integrated waveguide is studied,which compensates the phase difference caused by the unequal cm structure by adjusting the through holes at the T-shaped junction;and,the Chebyshev antenna synthesis method is used to reduce the sidelobe level of the antenna,and the designed T-type unequal power divider with phase balance is cascaded to form one minute.Finally,a high gain,low sidelobe and high order mode integrated cavity array antenna with 8×8 elements is designed,which realizes the low sidelobe characteristics of radiation pattern in E and H planes.In addition,in order to test the antenna,the transition structure between rectangular waveguide and substrate integrated waveguide is also studied.For the dual-polarization application of automotive radar,based on the proposed radiation structure of high-order mode substrate integrated cavity,two resonant modes TM211 and TM12121 are generated in the cavity by coupling feeding the substrate integrated cavity through a cross-slot,and the dual-polarization radiation in the X and Y directions is generated.Then the feed network of the dual-polarization array antenna is designed and studied to avoid the cross-slot feeding of the T-type power divider.Based on the phase difference between the two output ports,a broadband phase-balanced power divider with double-layer substrate integrated waveguide structure is designed,and two feeding networks with 16-element array antenna are designed with T-type power divider.The cross-polarization of the antenna is improved by the orthogonal slot coupling feeding proposed in this paper,and the port isolation of the dual-polarized antenna is improved by the three-layer feeding network.A 4×4 elements high gain bipolar substrate integrated cavity array antenna is designed by combining antenna elements with bipolar feed network. |
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