328 IEEE Antennas and Propagation Magazine, Vol. 56, No. 6, December 2014 Antenna Applications Corner Sudhakar Rao Northrop Grumman Aerospace Systems One Spacepark Redondo Beach, CA 90278 USA Tel: +1 (310) 813-5405 E-mail: sudhakar.rao@ngc.com Nuria Llombart EEMCS, Delft University of Technology Mekelweg 4, 2628 CD, Delft, The Netherlands E-mail: n.llombartjuan@tudelft.nl Generating Contoured Beams for Malaysia Region by Using a Caustic Locus Graph N. H. Abd Rahman 1,2 , M. T. Islam 1 , N. Misran 1 , Y. Yamada 3 , and N. Michishita 4 1 Faculty of Engineering and Built Environment Universiti Kebangsaan Malaysia UKM Bangi, 43600 Selangor, Malaysia E-mail: n.huda@eng.ukm.my; titareq@gmail.com; bahiah@eng.ukm.my 2 Faculty of Electrical Engineering Universiti Teknologi MARA 40450 Shah Alam, Selangor, Malaysia 3 Malaysia Japan International Institute of Technology Universiti Teknologi Malaysia Kuala Lumpur Jalan Semarak, 54100 Kuala Lumpur, Malaysia E-mail: ndayamada@yahoo.co.jp 4 National Defense Academy 1-10-20 Hashirmizu, Yokosuka, Japan E-mail: naobumi@nda.ac.jp Abstract It is very important to achieve precisely contoured beams in satellite-communication applications. For the case of Malaysia, separate contoured beams for the peninsular (West Malaysia) and Borneo (East Malaysia) regions must be achieved. For this purpose, the calculation of accurate feed positions in widely distributed feed areas is considered one of the critical aspects in designing a contoured-beam antenna system. Although some equations for precise feed positions have been proposed in previous papers, a graphical expression for the feed positions seems more convenient. In this paper, firstly, several trials to achieve a universal feed-position graph that is applicable for any antenna’s f D (focal-length-to-diameter ratio) and any beam direction were conducted. For this purpose, receiving-mode ray tracings were performed for various f D values and beam directions in MATLAB. The accuracy of the universal feed-position