| Analysis and design of ultra-wideband (UWB) plane spiral antenna are researched in this paper. The research works with scientific projects are divided into two parts in this thesis. an ultra–wideband double-armed Archimedes spiral antenna at 1.5~12GHz is made in the first part. a kind of compound spiral antenna at 0.4~6GHz is developed in the second part.In the thesis, with the profound research on basic UWB theories, both theories and implementations of antenna design in UWB communication system are discussed in detail. The antenna was designed with ultra–wideband, high gain, miniaturization and measured. The test results indicate that both the designed antenna and balun present good circular polarization and wideband character during the whole frequency range, and can basically meet the engineering requirements.At first the antenna is an ultra–wideband double-armed Archimedes spiral antenna and fed by 50 ohm coaxial-cable. To match the balance structure and the wideband character of the antenna , its balun is microstrip line-parallel wire which is exponentially gradual type. Transmutative cavity was designed to improve the gain of antenna. On the basis of the analysis of the planar equiangular spiral antenna and the Archimedean spiral antenna, we induce a kind of equiangular spiral antenna terminated by Archimedean structures. This kind of compound spiral antenna can improve the low and high frequency properties and overcome the long antenna arm, large transmission loss and the consequently low efficiency of the Archimedean spiral antenna to a certain extent as well. |
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