SIW cavity based RF sensor for dielectric characterization of liquids

A novel microwave SIW cavity based microfluidic sensor is designed and fabricated for detection and determination of dielectric constant of common liquids at 2.45 GHz. The technique is based on material perturbation theory. The developed sensor is the miniaturized version of the conventional rectangular cavity where the lateral walls are shorted with copper film coating. The proposed sensor is planar, highly sensitive, cost effective and about 100 times smaller than corresponding waveguide cavity. The electric coupling is provided by means of 3.5 mm SMA connector. In this paper, the calibration of fabricated SIW cavity is performed with water which provides easier way to calculate coefficients of perturbation. Various types of liquids are tested to verify the sensitivity and obtained results are in close agreement with the published data.