A multiphase direct-digital-synthesis sinewave generator for high-accuracy impedance comparison

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