Affiliations: [a] Antenna Research Group, Faculty of Electrical Engineering, Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia | [b] Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia | [c] Malaysia Japan International Institute of Technology, Universiti Teknologi Malaysia Kuala Lumpur, Jalan Semarak, Kuala Lumpur, Malaysia
Correspondence:
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Corresponding author: N.H. Abd Rahman, Antenna Research Group, Faculty of Electrical Engineering, Universiti Teknologi MARA, Shah Alam, 40450, Selangor, Malaysia. E-mail:nurulhuda0340@salam.uitm.edu.my
Abstract: Design and analysis of a shaped-beam 12.2 GHz
array-fed reflector antenna for broadcasting satellite application and its
significant performance improvement are presented in this paper. In the
beginning, an elementary design employing a cluster of feed horns
illuminating a single reflector has been proposed for multi beam antenna
(MBA) system to produce contoured beam for Peninsular Malaysia. In this
configuration, the horn positions were determined precisely through a newly
developed caustic locus graph, which is the simplified technique for
calculating the exact feed locations in both elevation and azimuth plane.
The accuracy of the two-dimensional caustic locus graph, which was developed
based on a ray tracing approach, has been verified through EM simulations. A
universal feed position equation, derived from the technique has been very
useful in designing the multiple feed structures employed in this research
to ensure optimum radiation to the exact locations on the earth. Based on
the initial design (a cluster of feed horns) due to the small size of the
coverage area, an issue with regards to physical constructability of the
feed horns is raised. To solve this problem, the MBA is modified by
utilizing 18-element microstrip array as the feed, where each element
positions are calculated by using the same caustic model. In this approach,
calculations of accurate feed positions and optimum excitation coefficients
in widely distributed feed areas are considered as among the most critical
aspects in designing the shaped-beam antenna system. By using the proposed
solution, the preceding issue is solved and higher gain shaped-beam coverage
with optimized radiation pattern is generated. This paper shows the results
of the contoured beam antenna that have been achieved for beam scanned over
a small coverage size of approximately 0.9° long and 0.5° wide.
Small variation of radiation level, which is less than 3 dB within the EOC,
is also demonstrated in the performance analysis.
