Design of Substrate-Integrated Waveguide Loading Multiple Complementary Open Resonant Rings (CSRRs) for Dielectric Constant Measurement

Abstract

In order to solve the low-sensitivity problem of the dielectric constant with the resonant cavity method, a sensor based on a substrate-integrated waveguide structure loaded with a multi-complementary open resonant ring is proposed. With the enhanced resonance characteristics of the sensor, this design realized the measurement of complex dielectric constants in a wide range. The frequency selectivity of the sensor is improved by the high-quality factor of the substrate-integrated waveguide. By loading three complementary resonant rings with different opening directions in the ground plane, a deeper notch and better out-of-band suppression are achieved. The effect of the complex dielectric constant on both resonant frequency and quality factor is discussed by calculating the material under test with a known dielectric constant. Simulation and experimental results show that a resonance frequency offset of 102 MHz for the per unit dielectric constant is achieved. A wide frequency offset is the prerequisite for accurate measurement. The measurement results of four plates match well with the standard values, with a relative error of the real part of the dielectric constant of less than 2% and an error of less than 0.0099 for the imaginary part.

Microwave Sensors Based on Resonant Elements

“…Paper [ 73 ] proposes a method for the measurement of the complex dielectric constant of solid slabs that combines three CSRRs (complementary split-ring resonators) with different orientations with a substrate integrated waveguide (SIW). Such combination results in a sensor with high sensitivity and wide input dynamic range.…”

Design of a High Sensitivity Microwave Sensor for Liquid Dielectric Constant Measurement

“…The resonant frequency and electric field distribution of the sensor are fixed in a certain resonant mode. When the LUT is placed in the concentrated part of the electric field of the sensor, the electric field distribution of the sensor will be disturbed by the liquid to change its resonant frequency [ 23 , 24 , 25 ]. According to the change in resonance frequency, the relative dielectric constant of the LUT can be calculated by the formula.…”

Microwave Dual-Crack Sensor with a High Q-Factor Using the TE20 Resonance of a Complementary Split-Ring Resonator on a Substrate-Integrated Waveguide

“…In this paper, we produce a high Q-factor (~200) for a multi-crack sensor by integrating CSRRs with a higher-mode SIW. A SIW is a planar structure that offers additional functionalities over traditional waveguides, and attempts have been made to combine meta-material structures with a SIW to increase the Q-factor and sensitivity or reduce the sensor size [ 68 , 69 , 70 , 71 , 72 , 73 , 74 ]. However, combining CSRRs with a higher-mode SIW to separate and concentrate E-fields is proposed for the first time in the present study to enable multi-crack detection with a high Q-factor.…”