Determination of MMIC Transmission Line Parameters from Half-Wavelength Resonances

A new method of measuring MMIC transmission-line parameters is presented. The characteristic impedance ZL(¿) and the propagation constant ¿L(¿) are extracted from the admittance matrix that can be easily obtained from a two-port S-parameter measurement. For lines longer than half a wavelength, resonances occur that are utilized to determine the line parameters from an analytical model of the resonance behaviour. The main advantages of this method are: 1. Long lines can be measured, which provides better accuracy for attenuation and phase velocity. 2. At resonant frequencies the elements of the admittance matrix are only weakly disturbed by the networks embedding the line under test (this applies to both on-wafer and test-fixture measurement systems). 3. All parameters can be extracted from one line. Examples of coplanar transmission-line parameters for frequencies up to 110 GHz are given.