Characterization of Material Properties for Tunable Reflectarray Antenna Design

The emerging field of communications has increased the demand of electronically tunable reflectarray antennas. Substrate material properties play at1 important role in the design of reflectamy antennas. Variable permittivity materials such as liquid crystals and fenoelectrics have received great deal of attention due to their non-linear material properties. A comparative analysis behveen the properties of liquid crystals and ferroelectrics for tunable reflectarray antenna design has been carried out by using Finite Integral Method (FIM). A thorough investigation based on reflectarray design analysis and tunable bias voltages of different non-linear materials is provided. It has been shown that due to higher dielectric permittivity values of non-linear materials, fenoelectrics require higher bias voltages for electronic tunability, as compared to liquid crystal materials. Barium skontium titanate (BST) with a dielectric permittivity ranging from 300 to 360 has been used as a fenoelectric substrate material to design a rectangular patch reflectarray which offers a frequency tunability of 3 GHz. The results show that ferroelectrics are only applicable for high frequency reflectarray operation due to materials' higher permittivity values. Furthermore a rectangular patch reflectarmy antenna printed on 1 mm thick different liquid crystal materials has also been designed based on FIM. It has been shown that as the dielectric anisotropy of substrate material increases from 0.17 to 0.45, the frequency tunablity and dynamic phase range of reflectarray antenna also increase from 372 MHz to 795 MHz and 90' to 1 609, respectively.