International Symposium on Antennas and Propagation
A New Ultra wideband Omni directional Antenna
Behrouz Heydari, Ali Afzali, Hossein Rabiee Goodarzi,
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The necessity to ultra wideband and omni directional antennas, have caused to increase the use of these kinds of antennas in military and industrial applications. The primaries of these antennas are the dipole and monopole (if a half-space is to be illuminated). The problem of these omni directional antennas is their narrow bandwidth that we can use a plate instead of a string of wire in order to solve this problem . After that circular-disc antennas (figure 1) , half-disc antennas (figure 2)  and planar inverted cone antenna (PICA) (figure 3) were propounded . Although the above antennas have the preference of being ultra wideband and have simple structure, but are able to get just one kind of polarization .In this essay is tried to introduce a new sample of omni directional antenna with frequency bandwidth of 4:1 and acceptable VSWR which is able to get all kind of polarization by changing in the structure of PICA antenna and the related Ground plane. Also we have tried to have maximum directivity in angels 0° to 30° to axis z which will be preceded in the following.