Comparison of calculation techniques ofconstant VSWR impedance circle: evaluation of power transistors robustness

This paper determines the locus of points of constant output voltage standing wave ratio (VSWR) around the load optimal impedance at the fundamental frequency. The proposed resolution has no hypothesis and there is a solution for whatever impedance. This resolution is very helpful to determine the power transistors robustness. Some measurements results are presented on a Si/SiGe HBT of STMicroelectronics technology. The measurements are realized on two multi-harmonic load-pull test-benches: one passive and one active