Research On Electrically Beam Scanning Microstrip Reflectarray Antennas

With the rapid development of modern wireless communications, high-gainantennas with beam scanning capability have received more and more attentions, and theelectronically beam scanning reflectarray antenna is the most prominent. Compared tothe conventional reflectors and phased array antennas, the reflectarray antenna has theadvantages of low cost, low loss, high radiation efficiency and high precision of beamcontrolling. After all, the reflectarray antenna is widely used in microwavecommunication, satellite communication and radar fields.The development background and overseas research status are presented in the first.By introducing the basic theories of the reflectarray antenna, this dissertation explains thebasic operating principle and research methods in details, including the calculation ofscatter field, analysis of the element, design of the feed antenna and the derivation of theradiation efficiency. Besides, the center feed and offset feed microstrip reflectarrayantenna are design respectively, the simulation results show that the characteristics of theproposed antenna have a good agreement with the original scheduled requirements andtarget. And that is to say, the theories of the reflectarray antenna and the design procedureare correct and reliable.Finally, a novel reflectarray element etched by microwave varactor diodes isproposed. The active element allows continuous tuning of the scatter wave’s phase over a360deg range, and it has a quasi-linearity phase distribution versus the capacitancecharacteristics. Furthermore, this dissertation proposed a center feed array antenna, whichis consist of349novel active elements. By adjusting the whole bias voltage of thevaractor diodes on the reflector, the antenna can realize the scanning of the main beam intwo-dimensions plane with high radiation efficiency, and the azimuth angle is less than2degree. In addition, the realization method of the multi-beam is presented at last based onthe former reflectarray antenna design, and the radiation efficiency is improvedremarkable.