The purpose of this invention is to provide with a method for continuous and accurate measurement of the effective dielectric constant and the dielectric loss of a dielectric material at the same condition as it is implemented in actual circuits. Another purpose of this invention is to improve the high frequency circuit design accuracy by providing with a design method using the actual wavelength-shortening ratio of the circuit that is obtained through the measurement of circuit impedance at the same condition as the circuit is practically used. The high frequency measurement method for dielectric materials of this invention is characterized as; it measures amplitude and phase variations of the electric field component of an electromagnetic wave along its propagation direction on a high frequency transmission line which is actually implemented as a microstrip line, by using a device whose refraction index changes according to the electric field (or an E-O prober using Pockels Effect), in order to get effective dielectric constant and dielectric loss of said transmission line. The high frequency circuit design method of this invention is characterized as; phase variation rate of the electric field component of an electromagnetic wave along its propagation direction on a high frequency transmission line which is actually implemented as a microstrip line is measured by using a device whose refraction index changes according to the electric field (or an E-O prober using Pockels Effect), said phase variation rate is used to derive the wavelength-shortening ratio of said transmission line and said wavelength-shortening ratio is used for the high frequency circuit design. <IMAGE>
