Circuit Aspects of Parametric Amplifiers
Helmut Seidel, Göran Herrmann · IRE Transactions on Broadcast and Television Receivers · 1959
Parametric amplifiers are distinguished from most active networks in that power is taken directly from an a-c source and that the phase of this source is significant in the amplification process. As a consequence of the harmonic spectrum produced by the interaction of the power source (pump) and the nonlinear element, the introduction of a small signal generates a pair of sidebands about each harmonic. Networks with variable parameters may be handled with an extension of the conventional formalism into one of frequency as well as spatial scattering.