2. Spectral purity

2.1 Definition

An ideal oscillator provides a signal of constant frequency ν ₀ and amplitude V ₀ : V(t) = V ₀ cos (2πν ₀ t).

In practice, noise sources internal to the oscillator circuit induce random modulation of the signal's phase and amplitude. The real signal is then represented by :

where ϕ(t) and α(t) are random variables...