Comparison of microstrip line and grounded coplanar waveguide as microwave sensor for dielectric measurements

Among all the microwave dielectric sensors, the planar transmission line can be integrated underneath a RFID tag for IoT application. In planar transmission line method, the measurement performance and sensitivity are significantly affected by the geometry of a planar line used. Yet there are not many comparison studies when uses as a sensor for dielectric measurements. In this paper, microstrip line (ML) and grounded coplanar waveguide (GCPW) were designed and analysed for frequency range 150 kHz to 8 GHz. The transmission coefficient of ML and GCPW covered with sample of various dielectric values were calculated and compared to the measurements. The normalised measurement results were found in good agreement with the calculated results for samples with dielectric constant of less than 30 and frequency of not more than 6 GHz. Besides, comparison between ML and GCPW found that ML has higher stability while GCPW provides higher sensitivity measurements.