Generating Contoured Beams for Malaysia Region by Using a Caustic Locus Graph [Antenna Applications Corner]

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 graph was verified through radiation-pattern calculations by using the FEKO electromagnetic solver. Based on the proposed graph, the positions of the array elements for array feed configurations for the peninsular and Borneo regions were next determined. For the array feed, through observation of the calculated contoured beams by electromagnetic simulations, the optimum excitation coefficients of each radiating element were determined. Finally, excellent contoured beams were ensured through electromagnetic simulations.