Simple Dual-Feed Dual-Circular Polarization Antenna with High Isolation

A dual-feed antenna system with circular polarization (CP) diversity and high isolation is proposed in this paper. The proposed antenna consists of two bent monopole antennas and an isosceles triangular partial GND on a single layer. To simply design an antenna with dual -feed dual-CP characteristics, CP bandwidth (BW) is optimized based on a single antenna. The proposed antenna is structurally different from conventional antennas in three ways. Structural asymmetry is realized by bending the shape of the antenna and moving the position, and thus good CP characteristics are obtained. The feeding structure is changed from a linear type to a meander type. As a result, a single monopole antenna has a CP BW of 36%. Next, an antenna system with dual-CP characteristics is introduced by implementing two monopole antennas on a single layer. In this structure, the resonant frequency is controlled by the antenna geometrical parameters, and the null frequency at S21 is controlled by the distance between the two antennas. The measured results show that the CP BW of the proposed antenna is 40.6% (1.51-2.28 GHz). The measured isolation is below-20 dB within the operating BW.