Design Of Marine Radar Microstrip Array Antenna Based On An Optimization Algorithm

Ship radar is essential to ensure the safety of ship navigation.Marine radar antennas require the performance of narrow half power beamwidth(HPBW)and low side lobe level(SLL),but the two usually present a mutually restrictive relationship.The waveguide slot antenna has good performance but high cost,while the low-cost microstrip antenna is difficult to achieve both narrow HPBW and low SLL.Therefore,the high-performance marine radar antenna with microstrip structure needs to be further studied.In this thesis,the X-band low-SLL microstrip array antenna is designed using the IABC＿Kmeans hybrid algorithm combining the improved artificial bee colony(IABC)and K-means clustering algorithm,and the near-zero refractive index metamaterials(NZIMs)are loaded on the array antenna to further increase the gain and improve the HPBW.The thesis mainly includes the following contents:(1)The detailed steps and implementation ideas of the IABC＿Kmeans algorithm are introduced,and Matlab is used to program the algorithm.The algorithm can effectively optimize the array factor pattern of the array antenna and obtain the appropriate current distribution.Linearly polarized and circularly polarized microstrip array antennas are designed using the optimized current distribution.The antenna with an operating frequency of9.4 GHz consists of 32 element antennas arranged in a 2×16 array.The patch directions of the two rows of linear arrays are opposite and the feeding point is shifted by a quarter wavelength,so as to realize the superposition of the radiation fields of each element.This arrangement can make the patch spacing of the two linear arrays smaller without being restricted by the feeding network,thereby greatly reducing the vertical SLL,which can reduce the interference of sea clutter and airborne objects for ship radars.The gain of the linearly polarized antenna is20.45 d Bi,the HPBW in the horizontal plane is 5.9°,and the SLL is-32.14 d B;the gain of the circularly polarized antenna is 20.31 d Bic,the HPBW in the horizontal plane is 6.4°,the SLL is-27.42 d B,and the axial ratio is 0.27 d B.The experimental results show that the IABC＿Kmeans algorithm can effectively optimize the SLL of the array antenna and is suitable for antenna design.(2)A NZIMs is designed and loaded on the element antenna.After loading three layers of 5×5 NZIMs,the gain of the element antenna is increased by 6.52 d B,and the HPBW of the E-plane and H-plane is reduced by 47° and 79.8°,respectively.The effectiveness and feasibility of improving the antenna performance are verified.A three-layer 7×33 NZIMs array is loaded on the two array antennas to further increase the gain and reduce the vertical HPBW.After loading NZIMs,the gain of the circularly polarized antenna at 9.4 GHz is 22.5d Bic,which is increased by 2.2 d B,the HPBW in the horizontal plane is 5.8°,and the SLL is-28.33 d B;the cross-polarization level in the maximum radiation direction is-34.75 d B,the axial ratio is 0.32 d B,and the antenna is right-handed circularly polarized.After loading NZIMs,the measured gain results of the linearly polarized antenna is 22.72 d Bi at 9.4 GHz,which is consistent with the simulated results.The horizontal HPBW is 5.8° and the SLL is-30.66 d B;the vertical HPBW is 31° and the SLL is-26.78 d B.The experimental results show that the performance of the array antenna is significantly improved after loading NZIMs,which has application value for marine radar.