A Circularly Polarized Multibeam Transmitarray Antenna for Millimeter-Wave Applications

In this paper, a millimeter-wave (mm-W) circularly polarized (CP) multi-beam transmitarray antenna (TA) is proposed. The proposed multi-beam antenna (MBA) comprises a TA composed of multiple three-layer slotted metal receiver-transmitter (RT) unit cells, along with a set of CP planar source antennas fed by substrate integrated waveguide (SIW) transmission lines. By rotating the periodically arranged transmitting patches, 360° transmission phase compensation is achieved without changing the transmission amplitude. The source antennas include five SIW-fed metasurface-based radiators. A prototype with 15 × 15 unit cells was modeled, fabricated, assembled, and tested. Consistent with the theoretical estimation, the beam coverage range reached ±30°. The test results show that the proposed MBA has a peak broadside gain of 21.1 dBi and a scanning loss of 2.9 dB. Its 3 dB gain bandwidth is approximately 16.7%, and the 3 dB axial ratio (AR) bandwidth is approximately 19.4%. The proposed MBA has the strengths of low cost, easy fabrication, wide beam coverage range and low scan loss, and can be a great option for mm-W applications.