Research On 77GHz Microstrip Array Antenna

In recent years, the ownership of car in China has increased sharply. Meanwhile, the property damage and casualties caused by the traffic accidents are rising. In order to reduce the traffic accidents, automotive radar has got widespread attention of the automotive industry and research institutions. Now, many countries have allocated 24 GHz and 77 GHz frequency bands to vehicle radars. While, 24 GHz radar is mainly used in short-range radar, but 77 GHz radar can be used in both shortrange radar and long-range radar.In this dissertation, we proposed some millimeter-wave microstrip array antenna, that can be used in the automotive radar. We had designed two antenna arrays composed by the same elements, and one array composed by the elements with tapered width. All of them are composed of 16′8 elements. As for the two antenna arrays composed by the same elements, one follows the Dolph-Tchebyscheff(D-T) distribution, and the other one follows the exponential distribution.The antenna array composed by the same elements, which follows the D-T distribution, has a bandwidth of 1.46 GHz. At 77 GHz the antenna achieves the gain of 24.7 d Bi and its half power beamwidths(HPBW) for E plane and H plane are 12.6° and 6°respectively. The sidelobe level(SLL) is lower than-22 d B for both E plane and H plane. While, the antenna array composed by the same elements, which follows the exponential distribution, has a bandwidth of more than 5GHz. At 77 GHz the antenna achieves the gain of 23.9 d Bi and its HPBWs for E plane and H plane are 16°and 6.1°respectively. The SLL is lower than-22 d B for both E plane and H plane. The two arrays have about the same SLL, but the array that follows the D-T distribution has a narrow beamwidth and achieves higher gain. But the design of the D-T distribution antenna array is much more complex than the array follows exponential distribution.The antenna array composed by the elements with tapered width achieves the gain of 21.3d B at 77 GHz. Its HPBWs for E-plane and H-plane are 7.9° and 11.8° respectively. The SLL of the E plane is-18.9d B, and the SLL of the H plane is-17 d B. The pattern of the E-plane is determined by 16 linear series fed rectangular microstrip patches with tapered width, the width of the elements follows D-T distribution, so the radiation power of the elements also follows D-T distribution. The 2D array was composed by 8 linear arrays. When the array was fed by a corporate-feed network, it needs three-stage T-junction power divider network, the feed lines is much longer than the feed lines used in the series-fed arrays. The radiation from the feed lines used in the corporate-feed network is a serious problem. In this dissertation, the array was fed by a series-corporate hybrid feed network, which can shorten the feed lines significantly by just use one T-junction power divider network and two series feed lines, so the radiation pattern can be improved greatly.