Non-destructive measurement of dielectric constant using a 2.4 GHz microstrip patch antenna

Measurement of dielectric constant is important because it provides the electrical characteristics of the material which prove useful in research and development fields. A new technique to evaluate the dielectric constant or permittivity of the homogeneous dielectric material using a simple microstrip patch antenna has been developed in present work. The Microstrip patch antenna having resonant frequency of 2.4GHz is simulated and fabricated on FR4 dielectric material having thickness 1.6mm. The antenna, when tested on vector network analyzer shows resonant frequency at 2.401 GHz and reflection coefficient around -19 dB. The values of change in frequency and lS11l parameter are measured by placing Alumina Substrate as overlay on the patch antenna. Readings are taken by changing the thickness of overlay and by moving it over the width of the patch antenna. From these results empirical formulae for evaluating the dielectric constant of Alumina substrate are suggested.