Special considerations for alternatively designed digital phase angle standard

A novel approach to the design of a digital phase-angle standard is described in this paper. The use of a direct digital frequency synthesizer, acting as a digital sine sample generator, is discussed in detail. The possibilities for phase stability and phase resolution improvement are described and, as a result, an algorithm for the fast calculation of optimal input parameters is derived. Simulation and preliminary measurement results confirm the underlying theory. An auto-zero system with two independent measurement methods is proposed. The techniques described offer a very wide output frequency band, from dc to 1.5 MHz (for low-level voltages), with practically continuous frequency resolution and with a short-term phase stability and phase resolution of better than 0.001/spl deg/.