Temperature dependence of PHEMT-based LNA´s trade-off performance from scattering parameters and noise figure measurements

The design of low-noise amplifiers based on HEMT´s or PHEMT´s requires a knowledge of the trade-off performance. In this work, the optimum trade-off performance of an LNA for VSAT applications based on a commercial PHEMT series has been investigated vs. temperature, starting from a noise model fitted to the measured devices´ scattering parameters and noise figure values. This investigation has confirmed that for an LNA under changing ambient temperature, the combined Fmin-Gass, reported on the microwave low-noise device´s data sheets, no longer represents a useful design condition