The Role of the Activating Structure of Resonators on the Oscillator Phase Noise Correction

The importance of reducing the oscillator phase noise in most radio equipment, including communication systems, radio sensors and radar, has led to many solutions, one of which is the activation of resonator in the oscillator structure. In this paper, by presentation and analysis of x cases it is shown that the correction of the phase noise by activation of the resonator depends on the model of the resonator and its position in the oscillator and does not happen in all cases. It is also, shown that designing oscillators using extra active feedback loop is not always effective in reducing phase noise. Resonators whose equivalent resistance is in the path of the oscillator loop, do not require an extra active feedback loop in order to obtain the desired phase noise, and the losses are fully compensated by the amplifier which also plays the circuit oscillation role. Two oscillator structures; a series RLC resonator and an RLC resonator with resistor in parallel to capacitor, are compared and the results show that the phase noise is not changed by the extra active feedback loop in the first case but it is decreased by 18 dB in the second one.