A Hemispherical 3-D Null Steering Antenna for Circular Polarization

In this letter, a compact three-dimensional (3-D) null steering antenna is presented for circular polarization. Two high-isolated circularly polarized (CP) pattern modes, the broadside and the conical CP pattern modes, are synthesized for 3-D null steering in the upper hemisphere. The broadside CP pattern mode is generated by a corner-truncated patch, and the conical CP pattern mode is generated by four rotationally symmetric strips. By controlling the exciting power ratio and the relative phase delay of the two modes, continuous null steering is achieved in the elevation plane and the azimuth plane, respectively. A prototype of the proposed antenna operating at 1.575 GHz is fabricated and tested for the global position system (GPS) applications. The simulated and measured results verify the null steering performance of the proposed design.