A Dual-Band Resonator Sensor for Low Permittivity Characterization

Low permittivity materials are widely used in many electronic systems. However, dielectric measurement on low permittivity material is challenging. To address this difficulty, a dual-band resonant sensor is developed. The proposed sensor is an improved design from the complementary square spiral resonator (CSSR). By adding a square patch on top of the resonant cell, the local field is significantly increased. Therefore, the interaction between field and material is strengthened, resulting in an enhancement in measurement sensitivity. Owing to the increased sensitivity, low permittivity samples down to 1.19 can be measured with an accuracy of better than 3%. Such results demonstrate that this sensor is promising for low permittivity characterization. Moreover, this sensor is also capable of measuring samples with permittivity in the range of 2–10, with an accuracy of 5%. Furthermore, two resonances are created, enabling dual-band operation. The unloaded resonances take place at 2.00 and 5.41 GHz. Particularly, the measurement can be conducted simultaneously in the two operation bands. Measured results demonstrate that the accuracy and sensitivity are satisfactorily high and comparatively superior to the designs in the literature for low permittivity measurement.