Theoretical approach of the application of negative dynamic feedback in VCO oscillators

The theory of application of negative dynamic feedback in voltage controlled oscillators (VCOs) is presented. In the oscillator under consideration, amplitude stability vs. the frequency range is strongly dependent on the gain parameters of the active element as well as on the resonant circuit dissipative losses. The analysis of the oscillator amplitude behavior, on the basis of describing function theory, shows that the negative feedback eliminates these influences on the amplitude. Moreover, the oscillator can be dynamically controlled and holds the class A operation mode, which means the level of higher harmonic components can be reduced. The oscillator phase and amplitude noise can be improved because the up-conversion of 1/f noise to the oscillator base-band is strongly dependent on the oscillator signal level