Selection of proper substrate material is one of the major criterions in designing any antenna. The decisive parameters of a dielectric substrate are loss tangent and relative permittivity. This paper investigates the effect of loss tangent on UWB antenna performance by comparing the commercially available FR-4 substrate having dielectric constant 4.4 with loss tangent 0.02 and CMET_LD4.4 substrate having dielectric constant 4.4 with ultra-low loss tangent 0.0018. Printed octagonal monopole antenna geometry with tapered feed is selected for carrying out the study. Overall size of the antenna is 32 ¿¿ 32 mm. Antenna parameters such as return loss, radiation efficiency and gain are extensively analysed. All simulations are done using ANSYS HFSS 14. Prototypes of designed antennas have been fabricated through photo etching process and transmission properties are tested using a Vector Network Analyzer.
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