Design and analysis of defected ground structure (DGS) in normal mode helical antenna

This paper presented a study of a defected ground structure (DGS) which affects the performances of the normal mode helical antenna. Two (2) types of helical antennas have been designed; normal mode helical antenna (NMHA) or conventional antenna and the normal mode helical antenna with defected ground structure. The normal mode helical antennas connect to the circular aluminium ground plane. This study is focusing on the effects of defection in the circular aluminium ground plane on the helical design performance. Both designs operate at low frequency in the range of the UHF band. The DGS was proposed in this study in order to shift down the resonant frequency to the lower side. It was found that by using the DGS approach, the resonant frequency can be shifted to the lower side about 17.52% compared to conventional design without affecting the antenna size.