Study Of Miniaturization And Low Profile Of Broadband Planar Spiral Antenna

Planar spiral antenna is a kind of ultra wideband antenna, which has the advantages of wide band, circular polarization, small volume and easy conformal characteristic. It has been widely used in the field of national defense and mobile communication. Acording to the relevant theory, the design of miniaturization and low profile of the wideband planar spiral antennas is studied in this paper. The main research works are researched in the thesis as follows:(1) An “equiangular spiral + Archimedes spiral + slot seam” complex structure planar spiral antenna is designed. A “loaded double copper ring + across the resistor” complex improved method is applied to the optimization design of antenna. Finally, combining the CST and the Multi-Objective Particle Swarm Optimization(MOPSO) algorithm optimize parallel the parameters of resistance and copper ring by Matlab software and network that has 10 computers. The results of simulation show that the return loss is less than 10 dB from 1.1GHz up to 18 GHz, and the axial ratio is less than 3dB from 0.8GHz to 18 GHz. The new antenna has good characteristics of impedance and circular polarization, and its diameter is only 53.62 mm, which satisfies miniaturized designation.(2) A new type of miniaturized ultra-wideband photonic crystal buried balun is designed. Using buried type of “index gradient microstrip line- Parallel transmission line” complete the transformation from unbalanced cable to balanced antenna and impedance matching, also the cylindrical lattice array is applied to the design of balun. The results of simulation show that the photonic crystal buried balun can complete the impedance transformation from 50 ? to 130 ? at the frequency from 2GHz to 18 GHz, which has a good performance of S11 and S21. The volume of balun is only 20 mm ? 5mm ? 5mm, which satisfies the designation of low profile.(3) The integral simulation of antenna and feeding system is completed. The high frequency performance is deteriorated because the distance between Antenna and balun is small, which produces the coupling and mutual interference. In this paper, two methods are proposed to improve the antenna and feeding system based on finite conductivity layer and equivalent resistance surface.(4) Considering some applied occasions need a unidirectional planar spiral antenna, two kinds of methods are designed in this paper. One method is based on absorbing material, the other is based on FSS. The results of simulation show that the return loss, gain and axial ratio are all satisfied.(5) The antenna and feeding system are fabricated and measured. Measurement results are basically the same as the simulation results, which show that the system satisfies the requirements of the engineering application.