Optimization Study On Linear Arrays With Rectangular Patch Elements

Microstrip antennas have many good characteristics of small volume, light weight, thin section plane, easily manufacturing and matching with other shapes easily, so they are widely used in lots of fields such as wireless communications, radar, remote-sense, electronic warfare. To overcome the drawbacks of narrow bandwidth and low gain of single microstrip antenna, several microstrip antennas are usually used to construct an antenna array. But this will bring some difficult problems such as higher side lobe. Therefore, a great number of researchers try their best to solve the problems in recent years. The popular method is that microstrip antenna arrays are optimized to lower side lobe of antenna array.In this paper, the optimization of linear array with rectangular patch elements is studied. First of all, the function of main plain's orientation pattern of rectangular patch antenna is deduced by using transmission line method. Then, using finite difference time domain method, the near field is calculated. The radiate pattern of the far field is obtained by using near-zone-to-far-zone transformation theory. Also, the radiation pattern of the far field is compared with the pattern obtained by using transmission line method. Finally, the side lobe of linear array of rectangular patch antenna is effectively reduced by using genetic method on the condition of controlling the width of main lobe.There is some contradiction between the width of main lobe and the side lobe level. The distance between antenna elements and element's excitation currents are used as variables to optimize the side lobe of equal space linear array firstly. Subsequently, the distance between antenna elements is fixed and only element's excitation currents are used as variables to optimize the linear array. The optimized element excitation and radiate pattern by using genetic algorithms are compared with those of Chebyshev equal-sidelobe-array, and they are in good agreement. Thirdly, considering the main plain's radiate pattern, the linear array with rectangular patch elements is optimized. At last, all of spaces among array elements are used as variables to optimize the linear array. In a word, experimental results indicate that genetic algorithm is a good method for optimizing antenna array.