The measurement of the microwave scattering parameter of the chip GaAs MESFET is tried. The GaAs MESFET chip is placed on 30 mm by 20.5 mm carrier made of gold plated bronze and is connected to a microstrip transmission lines of 10 millimeter long fabricated on the allumina substrate through a bond wire. From the measurement of the ideal microstrip line fabricated from the same pattern, the microstrip lines of the jig is specified. The two port scattering parameter of the chip is then calculated from the measured data of the chip FET on jig, which included the discontinuity effect between the chip and the microstrip line and the inductance of the bonding wire. The calculated scattering parameter are accurate up to within the error of 5 percent in its amplitude degree for 8 GHz but about 10 percent and 50 degrees for 17 GHz in its amplitude and phase error, respectively.
