Magneto-Dielectric Characterization of Materials Using a Slow Wave CPW Based Compact RF Sensor

This work presents a novel slow-wave coplanar waveguide (CPW) based compact RF sensor for the characterization of magnetic and dielectric property of materials. Two modified split ring resonators (SRRs) are placed in the high field confined area achieved by the tapering of signal line. A SRR (SRR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_{\text{c }}$</tex>) is optimized for the high E-field confinement to estimate the dielectric properties shows a sensitivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.265 \text{GHz} / \varepsilon_{r}$</tex>, while the other SRR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{S R R}_{\mathbf{m}})$</tex> is designed for the measurement of magnetic properties shows the sensitivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.545 \text{GHz} / \mu_{\mathrm{r}}$</tex>. A calibration model is employed to correct the changes induced by the permittivity on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{S R R}_{\mathbf{m}}$</tex>. The proposed sensor is successfully utilized to characterize a few reference dielectric samples, and a synthesized magneto-dielectric material with the measurement error of less than 2 % makes it suitable for characterizing various magnetic and dielectric materials in RF and microwave applications.