A Sixteenth-Mode Substrate Integrated Waveguide Sensor Loaded With CCRR Resonator Used for Solid Permittivity Measurement

In this article, we propose a sixteenth-mode substrate integrated waveguide (SMSIW) planar microwave resonant sensor for solid permittivity measurement. The sensor incorporates a complementary curved ring resonator (CCRR) structure strategically positioned within the SMSIW cavity, where the electric field is most concentrated, effectively enhancing sensor performance. By loading material under test (MUT) onto the CCRR resonator, the electric field distribution around the sensor will be changed, resulting in a change in the resonant frequency of the sensor, which makes the sensor be able to measure permittivity of different solid materials efficiently. The article comprehensively analyzes the equivalent model of the sensor and conducts electromagnetic simulation experiments to validate its performance. In addition, the sensor’s performance is evaluated through experiments involving four different materials under test with dimensions of
$10\times 10\times 0.762$
mm. Experimental results show that the performance of the proposed sensor significantly improved, with an average sensitivity of 6.585%, an average resolution of 378.46 MHz/
$\Delta \varepsilon $
, and an impressively low error rate of only 0.7845%. The compact size with
$21\times 20\times 0.762$
mm of the sensor is in line with the trend of sensor miniaturization.