Comparative analysis of different defected waveguide structures towards monopole antenna

This paper presents different Defected Waveguide Structures (DWS) towards monopole antenna in Ultrawideband (UWB) frequencies. Monopole antenna is one of the potential candidate for UWB applications. Yet, it has poor directivity and gain due to low profile. Previous studies have made change on the configuration of monopole antenna itself to enhance gain. This paper proposes Defected Waveguide Structure to design externally with monopole antenna without reconfiguring monopole antenna. The waveguide is designed according dimension of monopole antenna. DWS waveguide is designed to have square, circle and spiral shapes in patch. Monopole antenna will act as input to those waveguides. The effects of different DWS waveguides towards monopole antenna will be investigated through antenna parameters. Meanwhile, the performances of DWS waveguides will be also analyzed through transmission coefficient (S
₂₁
) by setting two monopole antennas at the both open-ended surfaces of waveguide. In overall, monopole antenna achieves wide bandwidth of 8.54 GHz and highest efficiency. Monopole antenna with waveguide achieves narrow bandwidth of 2.76 GHz and low efficiency. Yet, it improves directivity obviously at 2GHz-7 GHz. Monopole antenna with all the DWS waveguide still maintain wide bandwidth of 8.6 GHz at the same time improve directivity and gain. Monopole antenna with square DWS waveguide shows highest directivity and gain at 2GHz-8.5 GHz. Monopole antenna with circle DWS waveguide demonstrates highest directivity and gain at 9GHz-10GHz. Monopole antenna with spiral DWS waveguide shows highest efficiency compares to others DWS waveguide.