Design of a low profile unidirectional UWB antenna for multi-service base station

A low profile unidirectional UWB antenna for multi-service base stations is presented in this paper. The main goal of this article is to design a low profile UWB antenna with a very stable and unidirectional radiation pattern. The proposed design is based on exciting the fundamental mode of a planar structure composed of two metallic rings, applying the Theory of Characteristics Modes. The feeding structure used to excite that mode is asymmetric and it is implemented with two CPW-ports (Co-planar Waveguide) with an impedance of 50, that bifurcate into two transmission lines with different lengths that are coupled to a circular aperture using the slot line model. The design has been obtained using a mathematical formulation, so it can be easily scaled to any frequency. In addition, an analysis of the operation of the structure is performed, according to the theory of characteristic modes. The -10 dB bandwidth obtained is 64.22%, with unidirectional radiation patterns. An antenna with these bandwidth, unidirectional and stability radiation pattern features can be used in services such as UMTS, LTE, WIMAX, WiFi, Bluethoot, etc.