Phase noise measurement

The other method of analyzing the noise disturbing an oscillator is to directly measure the phase spectral density of its output, using a phase noise measuring bench. This method is complementary to variance analysis: the latter is, as we have seen, particularly suited to the study of long-term stability (or, what is equivalent, to measuring the level of low-frequency noise h ₀ , h _–1 and h _–2 ), whereas phase noise measurement enables the level of high-frequency noise h ₊₁ and h ₊₂ to be measured directly. However, as the latter technique is highly dependent on the equipment used, we will confine ourselves here to giving the general principle and links with analysis...