Analysis of the Relationship between Noise Performance and Tuning Elements in MESFET VCOS

A theoretical analysis is described which is capable of predicting the influence of varactor diodes on the noise performance of MESFET voltage-controlled oscillators (VCOs). The technique is based on modelling non-linearities in the active devices using the quasi-static approach and it investigates the coupling of these devices through a linear three-port network. Steady-state oscillation conditions and the upconversion process produced by the interaction of the device models with a non-linear baseband noise source are discussed. A method employing an improved optimisation approach for the characterisation of device non-linearities is briefly considered.