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Improving Radiation Pattern of Low profile Ultrawideband Omnidirectional Antennas
  • Guang Li
Guang Li
National Key Laboratory of Microwave Imaging Technology

Corresponding Author:[email protected]

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Abstract

The pattern nulls of low profile ultrawideband (UWB) omnidirectional antennas in the main beam region cause the performance degradation of UWB wireless communication system in the null directions. In order to achieve ultrawide pattern bandwidth, a method to improve the radiation pattern of low profile UWB omnidirectional antennas is proposed in this letter. The mathematical operation of improving the radiation pattern is derived. A low profile UWB discone antenna is designed as a representative of the low profile UWB omnidirectional antennas, and the pattern characteristic is investigated. Then, the effects of the sleeves and modified cone on the antenna pattern and input impedance are analyzed using microwave simulation software. The results show that the pattern bandwidth is increased from 6.5:1 to 11.4:1. In the operating band, the pattern nulls along the entire phi plane are eliminated, and the minimum value of the pattern nulls is optimized from -35.0 to -12.4 dB. The corresponding gain exceeds 0.2 dBi in the main beam region of the theta direction 30° to 90°. The optimization is based on a constant volume of 0.774 ka. Finally, an antenna prototype is fabricated and the measurement results are consistent with the simulation results, verifying the validity of the method