A CSRR-Based Dual-Peaks Antenna Sensor for Full Characterization of Magneto-Dielectric Materials

This article proposes a complementary split-ring resonator (CSRR)-based antenna sensor for full characterization of magneto-dielectric materials. The CSRR structure can effectively confine the electric and magnetic fields on the surface of patch antenna in two different regions. In these two regions, both the complex permittivity and permeability of the materials can be determined by the shift in the resonance frequency and the variation of the magnitude. Since both the CSRR structure and the patch antenna are resonant systems, there would be two resonant peaks in the antenna sensor. The variation law of these two resonance peaks is complementary, which improves the measurement range of the complex permittivity and permeability. The relative permittivity ( $\epsilon _{\text {r}}$ ) is measured in the range of 1–90, and the dielectric loss (tan $\delta _{\text {e}}$ ) is 0–0.1. The relative permeability ( $\mu _{\text {r}}$ ) is measured in the range of 1–9, and the magnetic loss (tan $\delta _{\text {m}}$ ) is 0–0.9. In addition, a circuit model is proposed to explain the working principle of the antenna sensor. The antenna sensor can be represented by two $\textit {RLC}$ parallel resonances, and the influence of the material under test (MUT) on the port can be characterized by a series connection of capacitance and resistance. The simulation results show that the antenna sensor has good sensitivity. The sensitivities are 0.54% at $\epsilon _{\text {r}}=2$ , 0.06% at $\epsilon _{\text {r}}=90$ , and 1.17% at $\mu _{\text {r}}=2$ . The measurement errors of this antenna sensor are 0.89% at $\epsilon _{\text {r}}=3.41$ , 3.29% at $\epsilon _{\text {r}}=40.59$ , and 1.53% at $\mu _{\text {r}}=8.63$ , which is as good as other sensors.