Methods of voltage controlled generator frequency tuning to increasing synchronization stability of phase-locked loop system
DOI: 10.31673/2412-9070.2024.050634
DOI:
https://doi.org/10.31673/2412-9070.2024.050634Abstract
The work considers issues of increasing the stability of the operation of the PLL system by means of using of various methods of tuning the voltage-controlled oscillator (VCO).
In particular, the article proposes structural schemes for tuning the VCO, which in the synchronization mode with a slight error ensure the placement of the frequencies of the VCO and the reference generator (RG) in the middle of the synchronization area. Such tuning of the VCO usually occurs when the PLL system is been turning on in the case when the RG frequency is outside the synchronization band and accordingly the capture band of the system. In such a case, when the VCO is tuning in the PLL system occurs sequential change of three modes of operation, in particular, the beat, capture and synchronization (hold) modes.
Proposed methods of tuning the VCO provide an increase in the stability of the PLL system in the synchronization mode under the influence of adverse factors (disturbances): internal and external noises, interference of various nature, instabilities in the operation of the equipment, changes parameters of the surrounding environment (temperature, humidity, pressure, etc.).
Increasing the stability of the PLL system is achieved by tuning the frequency of the VCO almost to the frequency of the RG without using the "resource" of the phase detector, that is, at the moment of setting the synchronization mode, the output voltage of the phase detector is close to zero. As mentioned above, this corresponds to placing the frequencies of VCO and RG in hold mode as close as possible to the middle of the synchronization band of the PLL system.
The use of the proposed structural schemes for tuning the VCO is possible in both analog and digital radio engineering devices, where a PLL system is provided.
Keywords: phase-locked loop (PLL), PLL modes, PLL stability, VCO tuning.
