A broadband circularly polarized multi-beam folded transmitarray antenna

The multi-beam reflectarray and transmitarray (TA) antennas are new antennas that can have wide angular coverage. However, they are generally of large profiles. To address the issue, this article proposes a folded TA antenna of high gain and low profile that can produce circularly polarized (CP) multi-beams. It consists of a main-reflector, a TA, and a linearly polarized (LP) planar feeding array. It reflects an incident electromagnetic wave twice and converts polarization three times. It has a metasurface that carries out the broadband LP-to-CP conversion. A prototype is developed with a height of 1.8 lambda at 13 GHz. The experimental results show that the antenna can achieve a scanning range of +/- 10 degrees, a peak gain of 22 dBi, and an aperture efficiency of 20.8%. It has a 3-dB axial ratio bandwidth of 2.2 GHz (or 16.6%), covering 12.1-14.3 GHz. It features a low profile, high gain, low cost, and easy integration with communication systems (e.g., MIMO transceiver systems).