A.A. Sukhanov – Student, Moscow Institute of Physics and Technology (State University); 

Engineer, PJSC «Radiofizika» (Moscow)

E-mail: aleksandr.sukhanov@phystech.edu

I.I. Rubanov – Student, Moscow Institute of Physics and Technology (State University)

E-mail: rubanov.ii@phystech.edu

I.A. Grigoriev – Head of Sector, PJSC «Radiofizika» (Moscow) E-mail: iv.grigoryev@gmail.com

This paper introduces the research of the hybrid DDS-PLL synthesizer components interaction problems and determining the position of spurs that arise due to this effect in the output spectrum. In particular, the issue of interaction between DDS chips which are used as part of a hybrid synthesizer is being researched.

This paper introduces the research of the hybrid DDS-PLL synthesizer components interaction problems and determining the position of spurs that arise due to this effect in the output spectrum. In particular, the issue of interaction between DDS chips which are used as part of a hybrid synthesizer is being researched. This effect was studied in two typical hybrid DDS-PLL synthesizer models. In both synthesizers the PLL reference input has the same structure, which involves using the DDS output as a signal source, but the feedback loop in each scheme is implemented in its own way. In the first scheme, the second DDS chip is used directly in the feedback loop as a frequency fractional divider. In the second, it is a part of an additional frequency upconversion circuit outside the loop. The main goal is to determine position of spurs that appear as a result of two DDS chips’ interaction in the phase detector and further processing in the low-pass filter. During the work, both stationary spurs, whose position in the spectrum does not depend on the α1and α2 coefficients of the DDS for the hybrid synthesizer output signal with constant frequency, and non-stationary spurs, whose position depends on α1and α2, were researched. Selection criteria of DDS coefficients for the development of the hybrid DDS-PLL synthesizers with a low level of spurs were also presented.

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