On the Feasibility of Measuring Transistor Noise Parameters with an Interferometer

A new method is proposed for automatically measuring the noise parameters of microwave transistors. The basic apparatus is a heterodyne interferometer and this is used to measure the self and cross spectral powers associated with the noise waves which travel away from the input and output of the device under test (DUT). The interferometer can be fully calibrated by replacing the DUT with a mismatched shunt or series resistor. The technique is particularly suitable for characterising chip transistors, for measuring transistors at cryogenic temperatures, or indeed for any situation where the device is relatively inaccessible.