Broadband Circularly Polarized Planar Monopole Antenna With G-Shaped Parasitic Strip

The design of a broadband circularly polarized compact monopole antenna is proposed in this letter. By protruding a G-shaped parasitic strip into a C-shaped monopole antenna structure, two orthogonal modes are created with equal amplitude and 90° phase difference for circular polarization. A 3 dB axial-ratio bandwidth (ARBW) of the antenna is greatly extended by using a modified ground plane. With the help of these features, a compact broadband circularly polarized antenna is designed and fabricated. Experimental results show that the proposed antenna realizes –10 dB impedance bandwidth of 62.94% (3.92–7.52 GHz) and ARBW of 53.92% (4.28–7.44 GHz). Overall size of the proposed monopole antenna is <inline-formula><tex-math notation="LaTeX">$0.57{\lambda _0} \times 0.61{\lambda _0} \times 0.03{\lambda _0}$</tex-math></inline-formula>, where <inline-formula><tex-math notation="LaTeX">${\lambda _{0\;}}$</tex-math></inline-formula> is the free-space wavelength at the center frequency of the operating bandwidth. The proposed antenna is desirable for WLAN (5.15–5.85 GHz) applications and various wireless communication systems.