Normal Mode Helical Antenna on Small Circular Ground Plane

In this paper, it has been shown that input impedance matching for the Normal Mode Helical Antenna (NMHA) can be obtained by using a small circular ground plane (radius approximate to lambda/20) without any external impedance matching network. It also discusses the effect of the finite circular ground plane radius, the radius of wire on the input impedance, resonance frequency, and bandwidth of the NMHA. Further, the effects of different ground plane shapes and cupped shape ground plane bending in upward and downward directions on input impedance matching are presented. A prototype of NMHA has been fabricated to operate around 1.8 GHz and the measured results are in good agreement with the simulated results.