ANALYSIS OF METHOD TO DETERMINE DIELECTRIC CONSTANT OF SHEET MATERIALS USING APERTURE COUPLED MSA

Apart from application in communication systems, microstrip patch antennas are also used as resonators in estimation of dielectric properties of substrate materials required for design of microwave circuits. In addition to patch antennas, the striplines, ring and cavity resonators are widely popular for evaluation of dielectric constant of microwave substrate materials in laminate or sheet form. Four aperture coupled microstrip antennas have been designed using CST Microwave studio, which resonate at 3, 5, 7 and 10 GHz frequency respectively. Firstly the resonance frequency of each antenna is first measured with the reference dielectric material and then again measured with material under test (MUT) which is a part of dielectric medium. Effective dielectric constant is estimated by computing ratio of the two frequencies. From which dielectric constant of the MUT is extracted using capacitance model of the multilayer dielectric structure. The antenna design for 5 GHz has been fabricated using dielectric substrate of r ? = 2.94 and 0.4 mm thickness. Jig fixture assembly has also been fabricated for mounting of antenna structure and measurement set up. The method has been validated by simulation and measurements.