Analysis of Ku-Band steerable metamaterials reflectarray with tunable varactor diodes

• Published in: 2016 Progress in Electromagnetic Research Symposium (PIERS) pp. 709 - 713
• Main Authors: Jing Nie, Yan-Qing Tan, Chun-Lin Ji, Ruo-Peng Liu
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.08.2016
• Subjects: Antennas; Beam steering; Capacitance; Electromagnetics; Magnetic materials; Metamaterials; Varactors
• DOI: 10.1109/PIERS.2016.7734429

This paper presents an analysis of a steerable metamaterial reflectarray based on tunable varactor diodes for the Ku-Band. The proposed metamaterial structure is a periodic "K-shape" array that consists of a 12 by 12 matrix with several quantities of varactor diodes that are electronically modulated. The capacitance and series resistance are used to replace the traditional phase tuning methods, such as tuning the patch size, stub length, ring radius and so on. The resonant frequency and phase shift of the reflectarray are dominated by the operating capacitance of the varactor diodes. The design parameters of the unit cell with varactor diodes integrated across the gap between the "K-shape" gap have been investigated and optimized for frequencies between 12 GHz and 18 GHz. A Full-wave electromagnetic simulation demonstrates that the dynamic range of the phase reaches almost 300° from 11.5 GHz to 12.8 GHz with a capacitance varying from 0.14 pF to 1.14 pF. As the varactor capacitance increases, the resonant frequency is red-shifted, and the phase characteristics change with the capacitance at the frequency of interest. The maximum loss of the entire bandwidth is 2.85 dB, which is acceptable for practical applications. The beam steering range is approximately up to ±60°. The fine alignment of the control voltage for each varactor is critical for the metamaterial reflectarray design. The whole thickness of reflectarray is less than 2 millimeters, much thinner than the conventional mechanical and phased array beam scanning components. The integration of varactor diodes in tunable metamaterials makes the whole steerable component compact, flexibly controlled and low cost. This study shows the potential of a tunable metamertials reflectarray with beam steering techniques for further applications in Ku-Band satellite communications.