Smith chart formulation of performance characterisation for a microwave transistor

A scattering parameter theory of the performance characterisation for a bil ateral transistor is developed, where mismatching at the input port V-i is considered as a degree of freedom, and its combination with noise and gain is mapped as circles in the Gamma(in)-plane. Stability analysis is based on the unconditionally stable working area (USWA) concept, and all possible U SWA configurations are determined by the necessary and sufficient condition s. For each USWA configuration, the constrained maximum stable gain G(Tmax) and its termination couple (Gamma(S), Gamma(L)) are expressed as functions of the input VSWR V-i, noise figure F and the scattering S and noise N par ameter vectors. Furthermore, the possible incompatible cases for the (F, V- i, G(Tmax)) triplets are determined by their necessary and sufficient condi tions. A computer program based on this formulation is developed, and cross -relations among the (F, V-i, G(Tmax)) triplets have been utilised in obtai ning the performance contours at an operating frequency and bias condition.