Open-Waveguide dielectric measurements using complementary frequency selective surfaces (CFSS)

For the accurate characterization of the dielectric properties of substrates used in electromagnetic (EM) applications, robust techniques have been developed including plane-wave illumination, waveguides and resonators to meet this requirement. In previous work, the authors introduced a Waveguide-Resonator method; the resonator is the CFSS - complementary frequency selective surfaces, for dielectric constant measurements (C.C. Njoku et al., Proc. EuCAP, 2420–2422, 2013). Examining the resonant frequency, quality (Q) factor and insertion loss differences of the CFSS with and without the material under test (MUT), the permittivity and loss tangent of the MUT can be calculated. This method required the MUT cut to the WG aperture size and placed next to the CFSS within the WG in a closed environment. This paper examines the use of an open WG with one end covered by the CFSS and the sample placed over the WG flange to fully cover the aperture. Whilst the Q is low, this technique is versatile and low cost.