Determination of HEMT's noise parameters versus temperature using two measurement methods

A simplified approach for the determination of the noise parameters of high electron-mobility transistors (HEMT's) at microwave frequencies has already been presented for devices tested at room temperature. Such method relies on the extraction of a noisy circuit model from measurements of the scattering parameters and the noise figure at the fixed source impedance of 50 /spl Omega/ (namely, F/sub 50/). The noise parameters of the device are then computed by model simulation. They exhibited a very good agreement with the noise parameters determined by the experimental procedure. In the present work, commercial pseudomorphic HEMT'S have been characterized at different temperatures in the 6 GHz to 18 GHz frequency range for validating the use of a further simplified procedure. We here show how to determine the complete noise performance of the devices from a very reduced set of measurements, i.e., the scattering parameters at each selected temperature and the F/sub 50/ noise figure at room temperature. The computed noise parameters are compared with those determined by application of the measurement procedure. The results show that the very simplified method can be employed with a good degree of accuracy whenever rapid noise testing of HEMT's versus temperature is needed.