V.K. Shakurskiy1, M.V. Shakurskiy2

1,2 Povolzhskiy State University of Telecommunications & Informatics (Samara, Russia)

1 shakurskiy@mail.ru; 2 m.shakurskiy@gmail.com

Problem Statement. One of the disadvantages of harmonic oscillators using high-order digital filters is the multi-valued frequencies for which the amplitude and phase balance conditions are satisfied. This disadvantage is eliminated by introducing pre-correction of the equivalent phase-frequency characteristic (PFC) of the generator with the feedback disabled. Pre-correction allows to reduce the steepness of the typical PFC, obtain a zero PFC, and obtain an atypical PFC when positive frequency increments correspond to positive phase increments. In the latter case, the excited oscillations always fail.

Objective. To demonstrate the technology of tuning the equivalent PFC of a digital generator and to determine the cause of unstable oscillation generation when using an atypical section of the PFC.

Results. A scheme for pre-correction of the equivalent PFC for a harmonic signal is proposed. The technology of tuning the equivalent PFC using pre-correction is shown. A computer model of a digital harmonic oscillator is developed. The types of equivalent PFC corresponding to stable and unstable operation of the generator are determined. The cause of unstable operation of the generator when using an atypical section of the phase response, consisting in the frequency instability of oscillations, was found theoretically and confirmed experimentally.

Practical significance. The developed technology of pre-correction of the equivalent phase response of the digital generator allows for the effective use of high-order digital filters and simplification of generator controllability. Knowledge of the causes of self-oscillation breakdown allows for increasing the stability of complex multichannel systems with feedback.

Shakurskiy V.K., Shakurskiy M.V. Frequency instability and breakdown of self-oscillations in digital generators with atypical phase-frequency characteristics. Radiotekhnika. 2025. V. 89. № 2. P. 129−135. DOI: https://doi.org/10.18127/j00338486-202502-17 (In Russian)

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