Archimedean spiral antenna embedded with frequency selective surface for wideband applications
The potential applications such as satellite communication systems, critical military communications, radar warning systems and direction finding systems demand for high gain, uniform unidirectional radiation pattern and wideband antenna ranging from 3.1 GHz to 10.6 GHz. An Archimedean spiral...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English English |
| Published: |
2014
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| Subjects: | |
| Online Access: | http://eprints.uthm.edu.my/1417/1/24p%20ABDIRAHMAN%20MOHAMUD%20SHIRE.pdf http://eprints.uthm.edu.my/1417/2/ABDIRAHMAN%20MOHAMUD%20SHIRE%20COPYRIGHT%20DECLARATION.pdf http://eprints.uthm.edu.my/1417/3/ABDIRAHMAN%20MOHAMUD%20SHIRE%20WATERMARK.pdf http://eprints.uthm.edu.my/1417/ |
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| Summary: | The potential applications such as satellite communication systems, critical military
communications, radar warning systems and direction finding systems demand for high
gain, uniform unidirectional radiation pattern and wideband antenna ranging from 3.1
GHz to 10.6 GHz. An Archimedean spiral antenna is the most potential candidate in the
above mentioned applications as the antenna meets most of the above requirements.
However, the practical implementation of spiral antenna is challenged by its
bidirectional patterns, relatively low gain and the need for balanced feeding structures. A
moveable ground plane is proposed as the backing technique of the spiral antenna by
placing it at quarter wavelength behind spiral arms. Despite, the effects of the ground
plane on the antenna’s wideband properties, to enable the realization of a conformal
antenna without the loss of the antenna’s broadband characteristics, a radian sphere
theory is proposed for bandwidth improvement. Microstrip to parallel strip line balun is
proposed as the feeding structure of the spiral antenna. This balun has very large
bandwidth ranging from 2 GHz to 14 GHz. However, the separation of the ground plane
and the spiral arms at quarter wavelength at lower frequencies deteriorate the radiation
patterns at middle and higher frequencies. In order to improve the patterns, frequency
selective structure is proposed to embed in the cavity of the spiral antenna. The
optimized frequency selective surface improves the radiation pattern while maintaining
the other parameters such as the gain, bandwidth and axial ratio. All the proposed
designs are fabricated and measured. Both simulated and measured results have shown
good agreements. Finally, the results show that the proposed Archimedean spiral
antenna is the most suitable candidate for above mentioned applications because good
circularly polarized unidirectional radiation patterns and high gain of 8 dB to 11.2 dB
with bandwidth of more than 140% is obtained. |
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