Determination of Dielectric Constant and Dissipation Factor of Printed Circuit Board by Microstrip With Ring and Straight-Line Resonator Measurements

This paper presents the determination of dielectric constant (DK) and dissipation factor (DF) of a printed circuit board (PCB) by microstrip structure for its easy fabrication as a test coupon in manufacturing, as well as the mature empirical formulas to extract DK and DF from measured data of microstrip propagation constant $\gamma$. The ring and straight-line resonators (SLRs) are utilized to measure $\gamma$ and different results are observed. The explanations of the data deviations with the modified approaches are proposed in this paper to improve the consistency. With the measured $\gamma$, the DK value can be extracted by an iterative process where the propagation constant $\gamma$ is calculated based on an initial DK using the microstrip empirical formulas with dispersion effects, and the process is continued until reaching the acceptable error between calculated value and the measured $\gamma$. The DF is computed based on the solved DK with conductor loss. The proposed method is examined by the PCB material of RO3003 using probing technique up to the fifth order of resonant modes in the frequency range of 18 GHz to 90 GHz.