Noise, gain, and bandwidth characteristics of the variable parameter amplifier

An investigation has been made determining the noise, gain, and bandwidth characteristics of the general variable parameter system (i.e., a system similar to the type proposed by Landon' and Suhlz for amplification, conversion, and oscillation using ferrites). The basic circuit and its operation are illustrated in the following description. A variable capacitor is connected in series with two parallel resonant tank circuits, the three elements forming a closed loop. If the value of t.he capacitor is caused to vary sinusoidally about some average value at a frequency equal to t.he sum of the two resonant frequencies of the tank circuits, under the proper conditions oscillations can be set up in the tanks at their respective frequencies. Power is thus "pumped" from the varying capacitor into the tank circuits. Assume that an output load is coupled to one of the tanks and that the capacitor variation is reduced to a value just below the point where oscillations occur. Stable amplification then results for a signal coupled into the loaded tank at the tank's resonant frequency.