A comparison of two practical methods for measurement of the dielectric constant of LTCC substrates

This paper describes a comparison of two methods that are used in practice to determine the dielectric constant of RF and microwave substrates, namely the method of two microstrip lines (the microstrip differential phase method) and SPDR (split post dielectric resonator) method. We compare accuracy of these two methods that is subject mainly to geometry measurements. Our case study, based on an LTCC (low temperature co-fired ceramic) material with high relative permittivity (ε_r=16), shows that the method of two microstrip lines has potential to give almost identical results to those from the SPDR method. Our approach, however, requires several samples to be measured, and the obtained results exhibit quite large standard deviation. In addition to this the approach is very sensitive to the quality of samples under test.