A.V. Korolev1, S.G. Rykov2

1,2 JSC «All-Russian Scientific Research Institute of Radio Engineering» (Moscow, Russia)

Performing calculations related to the characteristics of direct digital synthesizers (DDS) requires knowledge of the coefficients included in the phase noise spectral density formulae. Since the DDS data sheets do not have these parameters, the problem arises of experimentally finding the coefficients based on the results of DDS phase noise measurement. To do this, it is necessary to analyze the expression for DDS phase noise and obtain formulae to estimate the coefficients for calculating DDS phase noise power spectral density.

As a result of the work performed, expressions were obtained that allow one to evaluate the coefficients of the formula for calculating the power spectral density of DDS phase noise. It is shown that when determining the coefficients for flicker noise, it is sufficient to measure the phase noise spectral density at two offset frequencies at two values ​​of clock frequencies. At the same time, the coefficients for fundamental noise can be found by solving a system of three equations for three combinations of clock and output frequencies. The calculation of coefficients for two types of DDS has been performed. To verify the correctness of the calculations, DDS phase noise measurements were performed at several values ​​of clock frequencies, DDS output signal frequencies with a change in the amplitude of the voltage of the sinusoidal clock. The difference between the calculated and measured phase noise does not exceed 2 dB. The proposed technique for estimating the coefficients of the formula for calculating the power spectral density of DDS phase noise can be used in calculating the characteristics of oscillation sources and signal synthesizers.

Korolev A.V., Rykov S.G. Experimental determination of the coefficients of the formula for calculating the phase noise of direct digital synthesizers. Radiotekhnika. 2022. V. 86. № 6. P. 96−108. DOI: https://doi.org/10.18127/j00338486-202206-13 (In Russian)

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