Phase noise and amplitude noise in DDS

Their article reports on the measurement of phase noise and amplitude noise of direct digital synthesizers (DDS), ultimately intended for precision time and frequency applications. The DDS noise S_φ(f) tends to scale down as 1/ν₀², until the noise hits the limit due to the output stage. The spurs, however disturbing in general, sink power from the white noise. Voltage noise can be more critical in the digital power supply than in the analog supply. Temperature fluctuations are an issue at 10^-3 ... 1 Hz Fourier frequency. Passive stabilization (thermal mass) proves to be useful. Other paramours affect the phase noise, like the clock frequency and power. The amplitude 1/f noise is of the order of -110 dB(V²/V²)/Hz in some reference (typical) conditions. Owing to the page and file size limitations, only a small part of the available data can be published here. An extended and free version of this article is available on http://rubiola.org and on http://arxiv.org.