A multiphase direct-digital-synthesis sinewave generator for high-accuracyimpedance comparison

In this paper, we report on the realization and characterization of a multi phase sinewave generator based on the direct-digital-synthesis technique us ing the latest Analog Devices direct-digital-synthesizer model AD9854. The generator is intended for use in high-accuracy impedance intercomparison se tups; thus, particular attention is paid to the stability and distortion of the sinewave output signal. The sinewave frequency can be tuned in the ran ge from 16 Hz to 16 kHz with a resolution < 10 mu Hz and with a relative fr equency short-term stability of 10(-7), whereas the sinewave long-term ampl itude stability is better than 10(-5) at full amplitude output. Signal ampl itude, frequency, and phase are monitored and set by means of a personal co mputer.