Load-pull experimental characterisation of active devices under non linear operation is a well proved technique still used in designing power amplifiers. When applied to the MMIC, this technique shall require special solutions to be extended to on-wafer devices up to millimetre waves. The paper presents an overview on the traditional load pull measurement techniques focusing the attention on millimetre wave application. An example of a fully automatic on-wafer system is described along with the more useful calibration techniques. By means of this test set a very detailed characterisation of devices can be carried out in short time, by setting the loads either at the fundamental or at the harmonic frequencies with independent controls.[Abstract]
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