Simulation of an Electronically Steerable Horn Antenna Array with Liquid Crystal Phase Shifters

This paper presents the simulation results for a phased antenna array with novel liquid crystal phase shifters (LCPSs). This work investigated the usability of this electronically steerable antenna technology in an inter-satellite link using a geostationary satellite. Due to the design of the LCPS and the aperture of the antenna, communication over the desired steering range of ±11° can only be accomplished if the manipulated phase number of the radio wave changes during the steering process. This results in the need for ideally instantaneous phase changes of 360° (jump) of some of the LCPSs during beam steering. Tests on first prototypes of the LCPS reveal that the currently employed high frequency liquid crystals (LC) require 44 s to 150 s to complete such a 360° phase jump, resulting in a severe drop in antenna gain during a portion of the time of these phase jumps. This study investigates the influence of these jumps on the communication link and compares different LCPS control techniques, used to optimize the distribution of phase jumps over time, by a figure of merit (FoM) for the link. Losses caused by the LCPSs within the waveguide are not considered in this paper. Mitigation methods to minimize the effects of out-of-phase LCPSs could aim at reducing the magnitude (optimized, staggered jumps) and/or duration of losses (faster LCPSs through faster LC or stronger E-field). None of these methods can avoid the loss in gain entirely, only minimize the duration or magnitude of loss. Therefore, a parametric study on phase shift speed vs. mean loss for various phase jump strategies was performed. Despite the slow alignment of the LCs and the resulting loss of gain, usable links could be identified with the investigated mitigation methods.