Mixed-mode analysis of the sensitivity of a radiofrequency oscillator disturbed by parasitic signals

The first step of this work is to study the susceptibility of a radiofrequency oscillator to deterministic disturbance sources. A Colpitts oscillator, working around a 4 GHz frequency, contains a heterojunction bipolar transistor with a silicon-germanium base as an active device. A mixed-mode analysis is involved, applying a microscopic drift diffusion model to the device, whereas the rest of the circuit used is governed by Kirchhoff s laws. We assume that this tool is very relevant to grasp the influence of intrinsic or extrinsic noisy sources of the oscillator. Our first simulation raw results motivate us to discuss, and perhaps extend, via some analytical models, the so-called impulse sensitivity function model. In this paper, we try to develop quantitative predictions about the phase noise of such oscillators, and to give some new tracks on this field.