In this paper, a printed elliptical monopole antenna for wideband circular polarization is proposed. The antenna's structure is asymmetric with regard to the microstrip line. The section of the ground plane that overlaps the elliptical patch is removed. With simulations, the relationship between the antenna's geometrical parameters and the antenna's axial ratio of circularly polarized wave is clarified. The operational principle for wideband circular polarization is explained by the simulated electric current distributions. The simulated and measured bandwidths of the 3dB-axial ratio with a 2-VSWR is approximately 88.4% (2.12GHz-5.47GHz) and 83.6% (2.20GHz-5.36GHz), respectively.

In this paper, a compact and wideband printed monopole antenna is proposed. The proposed antenna is fed by CPW line and has two stubs for impedance matching. A simple monopole element has resonance frequency of 2.5 GHz (low resonance frequency). High resonance frequency of 5.5 GHz and wideband characteristic can be achieved by adjusting the position and size of stubs. The designed antenna has dimension of 0.125 λ0 height and 0.16 λ0 width where λ0 is the free-space wavelength at 2.5 GHz. The measured bandwidth of the antenna is 3.56 GHz (2.47-6.03 GHz) for S11 less than -10 dB. FDTD method is used to analyze the proposed antenna with wideband characteristic.