LAUSR

A very small focal-to-diameter (F/D) ratio transmitarray for compact antenna test range (CATR) application is proposed in this article. The transmitarray comprises a feed antenna, a metasurface for phase modulation (MPM), and another one for amplitude modification (MAM). MPM and MAM are implemented using the same metasurface cell but with different cell selections and arrangements. A holistic phase-only design method determines whether the metasurface is for amplitude modification or phase modulation. A CATR collimator with an overall low profile is realized through the joint design of MAM and MPM. The proposed technique overcomes the limits of the ordinary metasurface lenses and enables plane wave generation with a short focal length and sizeable quiet zone. The resulting CATR demonstrates a 50% quiet zone of the aperture size with ±0.5-dB amplitude and ±5° phase errors by full-wave simulation. For further verification, a prototype is fabricated, and its experimental results confirm the simulations.