Abstract:
Measurements of material properties are essential in all fields of Science specially agriculture,
RF and civil engineering. More precisely, the measurement of dielectric constant of materials is
one of the challenging tasks. To find out dielectric constant of materials, different sensing
techniques are used. All of these sensors work on the principle of spectral shift in their resonance
frequencies corresponding to the change in the relative permittivity. These techniques involve
disadvantages such as large spectral dispersions with resonant shapes, high absorption losses and
complex measurement setups.
This thesis presents a novel sensing technique based on the shift in the polarization state of the
test sample through a metasurface to measure the unknown dielectric constant of the sample. The
polarization state sensing involves the detection of the co- and cross- currents induced on the
metasurface at single frequency. Their magnitudes are proportional to the magnitude and phase
of the reflected field components, thereby eliminating the need of frequency sweep. This unique
sensing through polarization state offers an additional degree of freedom over conventional
methods and therefore allows monochromatic sensing capability with high accuracy. The proof
of concept for polarization state sensing is demonstrated experimentally at microwave
frequencies and the dielectric characteristics of the samples embedded inside the metasensor are
extracted from calibrated polarization state data. This opens up new opportunities for realizing
low cost sensing device, while maintaining high sensitivity of overall sensor system.
This thesis also includes an anisotropic dual broadband polarization converter metasurface. The
surface can efficiently transform linearly polarized electromagnetic (EM) wave into its
orthogonal components in X and Ku bands.
