Design and analysis of a helical antenna printed on a layered dielectric hemisphere

• Main Author: Latef, Tarik Abdul
• Published: University of Sheffield 2012
• Subjects: 621.384135
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.575554

The development of a wide range and variety of mobile satellite communications and navigation systems such as GPS (Global Positioning System), INMARSAT and MSAT posing new challenges for the design of the antenna with circular polarization (GP) radiation due to their insensitivity to the Faraday effect or rotation. The Faraday rotation is a magneto-optical phenomenon that is an interaction between light and a magnetic field in a medium that causes a rotation of the plane of polarization. In this thesis, a conformal hemispherical helical antennas radiating in a homogeneous medium or printed on a layered dielectric hemisphere to achieve a wideband and wide beam circular polarization radiation with a high gain of -11dBi are rigorously analyzed and measured. A truncated hemispherical helical antenna with adjusted number of turns and hemisphere's radius is proposed to provide optimum 3dB AR bandwidth, 3dB AR beam-width and gain. Truncated helical antennas printed on single and layered dielectric hemispheres have been studied theoretically using the Dyadic Green's functions. Two different approaches are used to enhance the 3dB AR beam-width and bandwidth; the first is based on using a two-layer hemisphere in order to increase the 3dB AR beam-width. The second approach introduces a conformal parasitic wire in the original structure to increase the 3dB AR bandwidth. Due to poor impedance matching at the required GP frequency range, an integrated matching section has been incorporated in the configuration to improve the overlap between the Sll and AR bandwidths. Finally, to increase the gain, 3 element arrays of hemispherical helical antennas that are printed on two-layer hemispheres have been designed. The results obtained from 11 simulations have been verified with the experimental work. Theoretical and experimental results confirm that the proposed techniques to develop a low profile wideband and wide beam circularly polarized antenna are successful where 3dB AR bandwidth of -11 %, 3dB AR beam-width of 1360 and a gain of 11.35 dBi at the lowest AR frequency have been achieved and offer promising results for applications related to mobile communication systems.