Research On Electronically Steerable Leaky-wave Antenna Based On Liquid Crystal

In recent years, leaky-wave antenna has become the high concerned topic of contemporary antenna research because of its many advantages inc luding hign antenna efficiency, high direction and controllable gain. Especially, the beam of leaky- wave antenna has frequency scanning feature which means through loading electronic control materials, leaky- wave antenna can easily implement electronically scanning feature. However, there are still some main problems existing in electronically steerable leaky- wave antenna research, which are given as follow:I. Contemporary electronically steerable leaky- wave antennas are mainly based on solid microwave devices such as varactor. Because of the stray parameter and loss, this kind of electronically steerable leaky- wave antennas cannot work at K u frequency band and above.II. Up to now, there is little research available on the beam control method of leaky- wave antennas even though this problem is very important for electronically steerable leaky- wave antennas research.Aiming at the first problem, this the sis utilizes the liquid crystal material to design electronically steerable leaky- wave antennas. The design method of electronically steerable leaky- wave antennas based on liquid crystal is proposed in this graduation thesis and four kinds of electronically steerable leaky- wave antennas based on liquid crystal which work in X band and K u band are designed. Through changing the applied voltage of liquid crystal, the antennas are able to implement zero passage scanning feature. While scanning, antennas are always in a good matching state. In addit ion, for the antennas proposed, the perfusion and control method of liquid crystal are convenient, the ga in is high and the size is small.To achieve the beam control and shaped pattern synthesis of the antennas proposed in this the sis, the beam control method of electronically steerable leaky- wave antennas is stud ied. A method tha t applying different voltages to different un it cells of pe riod ic leaky- wave antennas is proposed. Using that method, we can achieve beam controlling as long as changing the applied voltages without changing the size parameters of antennas. Two kinds of intelligence algorithm including simulated annealing algorithm and genetic algorithm are used to achieve the control of main lobe direction, side lobe leve l, the stability of beam and so on. The results of intelligence algorithm and full wave simulation have good agreement.