Design Of A Microstrip Planar Antenna With Slow Sidelobe

Compared with a common array antenna, a microstrip array antenna has many excellences such as thinner section, smaller cubage, littler weight, simplifier structure and lower cost. But its application has been limited because of its narrower frequency bandwidth and higher sidelobe level. In this paper, a novel microstrip array antenna working on C band has been designed. The antenna is composed of 64 elements. Every element is an aperture-coupled microstrip antenna with wide frequency bandwidth. In this design, the elements are distributed according to the Dolph-Tchebyscheff amplitude illumination. The antenna can realize wider frequency bandwidth than 15%, lower sidelobe than -18dB and higher gain than 20dBi.From the design, we can get the following experiences:①An aperture-coupled micro-strip antenna can supply power for radiating patch through the coupling of the feed line and the patch by a rectangle slot. The antenna's bandwidth exceeds 30%( VSWR≤2). In addition, because the antenna's radiating patches are separated from the microstrip line by the ground plane, the feed net consists of many feed lines can be designed independently. The independent design of the feed net will not affect the radiation of the antenna.②The elements' distribution according to the Dolph-Tchebyscheff amplitude illumination can make the antenna get slower sidelobes and narrower mainlobe.③Binary power divider can realize the distribution and the synthesis of power according to various proportions. Binary power divider has wider frequency bandwidth and it is easy to be designed. When we use binary power divider, the same phase's feed of every element can be ensured. Because the currents on 64(8×8) elements are centrosymmetric, we can get the feed net of the whole array by analyzing and designing the feed net of one quadrant.④The coupling among elements has great effect on the sidelobe level of the array antenna.⑤In this design, we use Microwave Studio to simulate the characteristics of the element antenna and the array antenna. At the same time, we use Microwave Office to simulate the Characteristics of the feed net. The simulation result has given us many helps to design and optimize the antenna.