Circularly-Polarized Ring Slot Antenna Fed by a V-Shaped Coupling Strip

A design for circularly-polarized (CP) ring slot antennas is described. The antenna is fed by a V-shaped coupling strip loaded with a resistor. For the slot antenna with a thin slot width, the proposed feeding mechanism can directly generate good CP radiation and fine tuning of antenna parameters is unnecessary. When the slot width is increased, CP radiation with low axial ratio can also be obtained as long as the included angle of the V-shaped coupling strip is properly adjusted. Numerical analyses of the key parameters of the V-shaped coupling strip are provided. A number of the CP prototypes with various slot widths are fabricated. Experimental results demonstrate that the feeding mechanism can give good CP performances for the case that the slot width is varied from 0.008 to 0.09 ë0, and the antenna gain is not significantly degraded when the loading resistance is small enough.