Research On Ku Band Microstrip Reflectarray Antenna With Low Side-Lobe

Nowadays, with the rapid development of the wireless technology applications and the increasing demands of the radio spectrum resources, the radio spectrum resources have been nearly exhausted. In order to increase the efficiency on using limited frequency resource, the thesis focuses on the design of transmitting and receiving antenna used in the co-frequency co-time full duplex system(CCFD). This design attempts to build a structure from microstrip reflectarray antenna, and integrates transmitting feed, receiving feed and microstrip reflectarray into a system. Eventually, the antenna features high isolation between transmitting and receiving feed and high gain, low side lobe for radiation pattern under the CCFD. The contents of thesis can be summarized as follows:Firstly, a feed antenna is designed. For the reflectarray, feed antenna will directly affect the overall performance of the whole antenna system, especially the performance of radiation pattern. Thus by utilizing the additional higher modes, a dual-mode conical horn with equal E and H patterns is designed as the feed antenna.Secondly, phase compensation elements for the proposed reflectarray are accomplished. High linearity and wide phase compensation are the challenges for reflectarray elements design. In this paper, the element with a range of 454° is achieved by using two-layer patch structure to introduce two close resonance points.Thirdly, the reflectarray is designed based on the theory of phase compensation. In order to make the reflected and received signals point on the same direction at the same time, this thesis proposes an elliptical reflectarray depending on the symmetry and the reciprocity of feed horn. The elements on the reflectarray are mirror-symmetric about both long and short axis of the elliptical array. The transmitting and receiving feed are located at the same side of the reflectarray along the long axis and also mirror-symmetric about the normal plane of the array which is through the short axis. However two grating lobes appear in the radiation pattern for this structure, which will be suppressed by optimizing part of phase compensation elements using genetic algorithms(GAs).Fourthly, a reflectarray antenna is designed based on multilayer PCB process. It also features good performance with overall size of 300×240×3.2mm3. The measured gain of main lobe is 24.3 dBi at 15.3 GHz with 6° for 3dB beam width and the grating lobes are below-15.6 dB. The isolation bandwidth higher than 40 dB is 1.3GHz.Finally, work in the thesis is summarized and possible improvements are discussed.