Circularly polarized loop-line antennas

A novel miscrostrip line antenna consisting of loop radiation cells is analyzed using the method of moments. First, an open-loop line antenna is analyzed as a reference antenna. The analysis shows that, as the number of radiation cells is decreased, the reflected current increases to deteriorate the axial ratio. Next, a closed-loop line antenna is proposed. The antenna is characterized by its radiation mechanism where both the traveling and reflected currents contribute to the radiation of the same rotational sense of circular polarization. The number of the radiation cells is chosen to be four, where the reference antenna cannot radiate a CP wave. It is found that the antenna radiates a CP wave with an axial ratio of less than 3 dB in a frequency bandwidth of 3%, where the gain is approximately 15 dBi. These bandwidth and gain are also found to be comparable to those of a conventional array composed of four loop antennas.