A Retro-directive Array Antenna with 3-State Phase Shifter for Microwave Power Transfer

In microwave power transfer system, the large array antennas are necessary and should apply the retro-directive beamforming which is effective in Fresnel region. The retro-directive array antennas requires not only hundreds or thousands antennas but also RF chains. In this paper, for decreasing the cost and complexity of large array antennas, the focusing effect of retro-directive array antenna using low-bit phase shifter is analyzed. Also, a 3-state phase shifter is proposed for effective focusing effect. For testing the proposed antenna, the 16×1 retro-directive array antenna as a test-bed was implemented, and the power transfer were carried out.