Dispersion measurements of the first two higher-order modes in open microstrip

The short-circuited microstrip resonator, commonly used for measuring the dispersion of the fundamental mode in microstrip transmission line, is employed to determine the dispersion characteristics of the first two higher-order modes. Additionally to this method another simple technique has been developed for experimental investigations of the dominant and the first higher-order mode in open microstrip. In contrast to the resonance method the dispersion measurement can be performed here at any arbitrary frequency; this is very important for an accurate determination of the cut-off frequencies of the higher-order modes.