Reconfigurable holographic antenna with low sidelobe level based on liquid crystals

Abstract

A novel liquid crystal (LC)-based holographic antenna (HA) with low sidelobe level is proposed in this paper to achieve large beam scanning range and multi-beam scanning property. The operating principle and the design procedure of the LC HA are presented. The influence of the on-to-off ratio of the holographic array element on the reconfigurable HA's radiation characteristics is investigated. It is shown that the larger on-to-off ratio can reduce the sidelobe level of the reconfigurable HA, or decrease the iteration number of sidelobe optimization algorithms and enable the algorithms to converge to a much lower optimal sidelobe level. An effective design method to increase the array element's on-to-off ratio is proposed through introducing an auxiliary radiation component, which offsets the radiation for the turn off state and enhances the radiation for the turn on state. A prototype of the LC HA consisting of the elements with large on-to-off ratio is designed and simulated to demonstrate the design method and theoretical predictions. Results show that, benefiting from the enhanced on-to-off ratio, the LC HA naturally presents a sidelobe level of -12.2 dB at broadside without any optimization. Compared with previous work, the sidelobe level is 3.2 dB lower than the case without large on-to-off ratio. Moreover, the proposed LC HA shows a quite large beam scanning range rising from -57.7 degrees to +57.4 degrees and a dynamic multi-beam property.