K.A. Yakimenko1, V.V. Romashov2, K.K. Khramov3, A.N. Doktorov4, N.A. Sochneva5

1-4 Murom Institute (branch) Federal state budgetary Educational Institution of Higher Education
“Vladimir State University n.a. Alexader Grigoryevich and Nickolay Grigoryevich Stoletovs” (Murom, Russia)

5 Federal State Budgetary Educational Institution of Higher Education
“Vladimir State University n.a. Alexader Grigoryevich and Nickolay Grigoryevich Stoletovs” (Vladimir, Russia)

1 yakimenko.kirill@yandex.ru; 2 romashovmurom@mail.ru; 3 hramovkk@gmail.com; 4 doctorov_a_n@mail.ru; 5 sochnewa.natalya@yandex.ru

Problem statement. The trend in modern microwave electronics to transfer analog functions to the digital domain has led to the emergence and active use of high-speed digital-to-analog converters (DACs) in special operating modes in promising communication systems. However, optimization of power consumption and economic costs of signal generators (for example, through the use of simplified clock generators or by saving FPGA memory) leads to an increase in phase noise and nonlinear distortions in the output signal, which has a significant impact on the parameters of the communication system.

Goal. Evaluation of phase noise and nonlinear distortions of signal generators based on high-speed digital-to-analog converters, as well as the study of their effect on the parameters of a digital communication system.

Results. Expressions for estimating the spectral power density of phase noise of a signal generator based on a high-speed DAC are proposed. It is determined that the level of phase noise of the shaper is mainly determined by the noise of the clock generator. The jitter of the communication system was evaluated when using a surfactant generator and a PLL-based synthesizer as a clock generator. A mathematical model of the output signal of the shaper is proposed, taking into account nonlinear distortions caused by sampling, phase code truncation and amplitude quantization. A model of a communication system with multi-position quadrature amplitude modulation has been developed to evaluate parameters taking into account phase noise and nonlinear distortion of the shaper based on high-speed DACs. It is determined that the intrinsic phase noise of the signal generator leads to an increase in the probability of bit error (by about an order of magnitude compared to ideal formers). The use of surfactant generators as clock generators makes it possible to reduce the probability of bit errors of the communication system by 3-5 times compared with PLL-based synthesizers.

Practical significance. It is shown that the displacement of points in the signal constellation is mainly influenced by nonlinear distortions of the output signal of high-speed DACs caused by truncation of the phase code, as well as incomplete suppression of spectral components located in the neighboring Nyquist zone. The proposed mathematical apparatus makes it possible to determine the optimal frequency ratios in the structure of the shaper, at which the lowest values of the displacement of the constellation points are achieved.

Yakimenko K.A., Romashov V.V., Khramov K.K., Doktorov A.N., Sochneva N.A. The influence of phase noise and nonlinear distortions of high-speed digital-to-analog converters on the parameters of digital communication systems. Radiotekhnika. 2024. V. 88. № 6.
P. 137−148. DOI: https://doi.org/10.18127/j00338486-202406-17 (In Russian)

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