A Digital Beamforming Antenna for Space Based Solar Power Transmitting Array

This paper presents a beam-steerable quadrifilar helix antenna (QHA) on an artificial magnetic conductor (AMC) surface for space based solar power application. The AMC surface is composed of 8 × 8 square unit cells to suppress the surface current. By controlling the input phases to the QHA ports through a digital beamforming circuit, the circularly polarized (CP) patterns can be steered within the upper half space. To verify the working mechanism, two passive polyphase feed networks are employed in the measurement of the proposed QHA at 5.8 GHz. The measured results show the proposed antenna can steer the beam from boresight to 26 degrees in elevation without dropping the gain, while keeping the sidelobe level to -8.1 dB.