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 AD9853. The generator is intended for use in high-accuracy impedance intercomparison setups; thus, particular attention is paid to the stability and distortion of the sine wave output signal. The sinewave frequency can be tuned in the range from 16 Hz to 16 kHz with a resolution <10 μHz and with a relative frequency short-term stability of 10^-7, whereas the sinewave long-term amplitude stability is better than 10^-6 at full amplitude output. Signal amplitude, frequency, and phase are monitored and set by means of a personal computer