Study Of Miniaturization Of Broadband Planar Spiral Antenna

Planar spiral antennas have developed rapidly as one kind of wideband antenna.Because of the advantage of wideband, circular polarization, simple construction, lowprofile, small volume and low cost, they have been widely used in the field of nationaldefense and mobile communication. Now the development trend of planar spiral antennas iswideband, small volume and low power consumption. In the thesis, the design methods ofminiaturization of the wideband planar spiral antennas are studied.The major research works in the thesis can be summarized as the follows:(1) A novel automatic design approach for the miniaturization of Archimedean spiralantenna is given. Based on the MATLAB, the method of combining the CST and theMulti-Objective Particle Swarm Optimization (MOPSO) algorithm is applied to theoptimization design of Archimedean spiral antenna, which satisfies the requirement of theminiaturization design of aperture. The results of the simulation show the method is feasibleand the optimization can be done automatically without any human intervention. The newdesign antenna keeps good characteristics of impedance match and circular polarization,while its aperture size is reduced about37%compared with the traditional Archimedeanspiral antenna, which achieves the purpose of miniaturized design of aperture.(2) The miniaturized ultra-wideband planar spiral antenna and the wideband balun aredesigned based on the demand of project. The design is based on the novel quadratic formof planar spiral antenna. The results of simulation show the low end of the operatingfrequency is obviously lower than the traditional Archimedean spiral antenna and theequiangular spiral antenna. The aperture size of the quadratic form of planar spiral antennais just52mm, which satisfies the requirement of the miniaturization design. However, thebandwidth of axial ratio can’t meet the expected index. Then the method of loadingresistance among the terminal spiral arms broadens the bandwidth of axial ratio. The resultsof simulation show the quadratic form of planar spiral antenna with wideband balun canwork at the frequency range of2GHz to18GHz. Moreover, the each index has satisfied theexpected demands.(3) The dielectric embedded Archimedean spiral antenna is studied. The inputimpedance of this antenna is relatively low and more stable, which is beneficial toimpedance matching. Based on the dielectric embedded Archimedean spiral antenna, the low profile antenna is designed. A novel stripline-fed is used in the process of design. Theresults of simulation show that the Archimedean spiral antenna also has good impedancecharacteristics using stripline-fed method and the longitudinal size of the overall antenna isjust the thickness of dielectric-slab. The longitudinal size of antenna is greatly reducedcompared with traditional balun-fed antenna, which achieves the low profile design ofArchimedean spiral antenna (miniaturized design of longitudinal size).