Chapter 5

Overview of UWB Antennas 1

5.1. Classification of UWB antennas

This chapter is devoted to the presentation of the various antennas that present ultra wide band impedance matching and some techniques to improve their performances. In order to better understand their behavior, these structures will be classified by categories presenting each precise specificity. The frequency independent antennas, which present the property of being dimensioned identically at all the frequencies, will be initially presented. Their design is studied in order to enable them to preserve constant performances on several octaves. Some flared-shape elementary antennas with wide band characteristics will then be described. These evolutions of simple dipoles use the property according to which their bandwidth is related to their thickness. We can thus obtain ultra wide band (UWB) antennas with dipole-like radiation pattern.

The two last categories presented will be the antennas with progressive transition and the horn antennas. These structures are based on the impedance stability of transmission lines and waveguides. This characteristic is preserved by widening the feeding structure to gradually match the free space impedance. The ends of these antennas are also optimized to effectively radiate these guided waves.

5.2. Frequency independent antennas

The frequency independent antennas are certainly the UWB antennas most known, or in any case, most largely represented and studied in conventional ...

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