38-GHz Band High-Power MMIC Amplifier Design using Improved Load-Pull Method

To facilitate accurate amplifier design, the large-signal impedance of a GaAs FET with a 0.25-¿m-long gate was measured using an improved load-pull method. A new MMIC transformer was used in the measurement to transform the FET´s impedance into the coverage range of a twin sleeve tuner. The transformer as well as a wafer prober improved measurement accuracy. Two types of high-power amplifiers were designed using the measured large-signal impedance: one is composed of four FET cells with 400-¿m-wide gates and the other is composed of two FET cells with 600-¿m-wide gates. At 38 GHz and at 1-dB gain compression level, the former has an output power of 25.1 dBm and the latter 23.5 dBm.