Analysis and design of a coaxial slot antenna for mobile telecommunications

It is foreseen that low-Earth orbit mobile satellites (LEO-MSAT) will be a promising choice to cover suburban and country sides. In contrast to the DBS antenna, the antenna for LEO-MSAT mobile terminals must have an upward-skewed main-beam for satellite tracking. Moreover, it must be low cost, high gain, high-efficiency, and small-in-size. In this paper, an attempt is made to employ a coaxial antenna with circumferential slots for mobile terminals. Because the antenna radiates through apertures and has a very simple configuration avoiding complicated feeding networks, it is expected to be of high efficiency. For antenna analysis, although an infinitely-long coaxial antenna with one slot has been thoroughly investigated, no rigorous analysis is carried out for a finitely-long coaxial antenna with multi-slots. Because the end effect and slot coupling are intractable for conventional methods using function approximation, such as the moment method and mode-matching method, the finite difference time-domain (FDTD) method is used to analyze the slot antenna. For further antenna design, the widths and positions of the slots should be strategically adjusted so that the radiation pattern of the antenna forms a desired upward-skewed donut for satellite tracking.