On the VCO oscillator with the negative dynamic feedback

The idea of the negative dynamic feedback in oscillators was studied in the past experimentally by J. Groszkowski (1952) and was shown that it could reduce the higher harmonic components and therefore a more frequency stable oscillator could be achieved. In this paper the application of the negative dynamic feedback in voltage controlled oscillators (VCO) is presented. In the oscillator under consideration, amplitude stability vs. the frequency range is strongly depended on the gain parameters of the active element as well as on the resonant circuit quality factor. So it is enough to prove that the amplitude is not sensitive on these influences. The analysis of the oscillator amplitude behavior, on the basis of describing function theory, show that the negative feedback eliminates these influences on the amplitude. Moreover, the oscillator can be dynamically controlled and holds the Class A operation mode, that means the level of higher harmonic components can be reduced. The verification of the above theory is presented with an octave frequency range VCO oscillator circuit at VHF band.