Altunin S. Improvement the noise immunity of software-controlled synchronization devices.

The thesis presents the contribution to the solution of the scientific task of development of methods for noise immunity improvement of software-controlled synchronization devices, and creation of firmware implementation of digital phase-locked loop (PLL) which possesses better marginal noise immunity. The method of digital synchronous detection was used to achieve this task, which allowed to reduce the noise threshold of the PLL and at the same time to maintain its dynamic characteristics. From the analysis of the references it was discovered that the available ways of noise immunity improvement are controversial because decreasing of the noise threshold is achieved by worsening of dynamic properties of the device. Some scientific works present solution to this problem, but the results of their research apply to analog PLLs and their research methods are limited by simulation and does not include experimental studies. The thesis presents a block diagram and mathematic model of a digital PLL with a modified phase detector (PD) containing a narrow-band filter (NBF) to maximize the filtering of noise and reduce the peak values of these interferences in order to provide the PD operation within the range of detector characteristics. High-pass filter (HPF) at the output of the detector compensates the suppression of the dynamic change of the useful signal. Simulation of the of classical and modified PLLs marginal noise immunity was carried out according to two criteria for determining the loss of synchronization. In both cases the use of modified phase detection allowed to decrease noise threshold by 2.5 dB without changing the static characteristic of the device. The results of the experiments qualitatively repeat the simulation and show the noise immunity improvement of the modified PD up to 2.5 dB in comparison with the classical device. Duration of transient processes in the modified device was reduced by approximately 1.5 times, indicating an improvement of dynamic properties compared to the classical device.