A Design of Dual-Wideband Planar Printed Antenna for Circular Polarization Diversity by Combining Slot and Monopole Modes

A novel dual-wideband antenna is designed for circular polarization (CP) diversity in this communication. It consists of a horseshoe-shaped slot, two
L
-shaped radiators, and two ports. The working principle of the horseshoe-shaped slot is half-wavelength slot mode, and the working principle of the
L
-shaped radiator is quarter-wavelength monopole mode. The slot mode is applied to produce two lower CP resonant frequencies of two bands and the monopole mode are used to generate two upper CP resonant frequencies of two bands. By narrowing these two modes of two bands, a dual-wideband CP antenna can be designed easily. When port 1 is excited and port 2 is matched, this antenna radiates left-hand CP wave at lower band and right-hand CP wave at upper band at the +
z
-direction. When exchanging the excited and matched ports, the radiation is reversed. The measured impedance bandwidths (
S
₁₁
<; -10$ dB) are 113% (0.7-2.52 GHz) and 60.2% (3.47-6.46 GHz). The measured 3 dB axial ratio bandwidths are 72.5% (1.17-2.5 GHz) and 56% (3.52-6.26 GHz). The isolation between the two ports is better than 15 dB.