Dielectric constant measurements using printed circuit techniques at microwave frequencies

Printed circuit (PC) substrates are frequently constructed from thin laminates such as low loss ceramics or composite materials. Testing such materials is quite a challenge because of their limited range of thicknesses: 0.2-3 mm. Special testing techniques are needed to evaluate the dielectric constant in this range. These techniques, with important modifications, have been especially developed in this work for copper clad printed circuit substrates but they can be utilized also for any thin laminate. Three methods are demonstrated in this paper: microstrip line resonator, printed stripline resonator and closed disk resonator. The theoretical background is presented briefly. Experimental fixtures, sample preparation and experimental results, covering a dielectric constant range of 2<ε´_r<20, are discussed in detail