The overall noise figures of diode parametric amplifier systems
Colin S. Aitchison, B.L. Humphreys, E.L. Neufeld · Proceedings of the Institution of Electrical Engineers · 1963
The paper gives details of the calculation of the overall noise figure of a system of a parametric amplifier followed by a receiver, and shows how a minimum overall noise figure can be obtained when the parametric amplifier is allowed to have a small positive output impedance and a transformer is placed between the two receivers. The overall noise figure thereby obtained is then expressed in terms of the bandwidths of the system. It is then possible to determine whether a specified parametric amplifier will give a desired combination of overall noise figure and bandwidth.This method of obtaining a low overall noise figure does not use gyrator networks.