Research On Digital Phase Locking Technology Based On Virtual Reconstruction

Phase-locked technology plays an important role in the field of time-frequency measurement and control.It can realize the synchronization between signal sources and output high-quality frequency signals.In recent years,the development of technologies such as navigation and positioning,Internet of Things,time service,and fifth-generation communication networks have placed higher demands on the frequency lock range,anti-interference ability,locking speed and accuracy of phase-locked loops.The implementation of phase-locked technology requires high-precision phase comparison technology to support,but phase comparators in existing phase-locked loop structures can only achieve phase comparison between signals of the same nominal value.If it is necessary to lock a signal with a large difference in frequency,it is usually necessary to normalize the frequency,resulting in an increase in the difficulty of circuit design and the introduction of additional noise.In this paper,the phase comparison technique is studied.By exploring the phase relationship between arbitrary periodic signals,it can be found that although the phase difference changes irregularly in the continuous comparison process,if the least common multiple period of the two comparison signals is used as the interval,phase group synchronization and phase group continuous characteristics can be found.This is an inherent law between periodic signals,making direct phase comparison in a wide frequency range possible,and high resolution of phase quantum and group phase quantum helps to improve the accuracy of phase comparison.On this basis,combined with the innovative virtual reconstruction technology,a virtual signal with the same frequency as the nominal value of the locked signal is introduced,and the gate is taken with the least common multiple period of the reference signal and the virtual signal or its integer multiple to achieve high resolution,no interval,continuous phase measurement.The comparison between the locked signal and the virtual signal is equivalent to the comparison between the locked signal and the reference signal,and the phase difference information between the two signals of which the nominal value is arbitrary can be directly obtained.In addition,this paper applies the virtual reconstruction phase comparison method to the phase-locked technology,and designs a new digital phase-locked control system for the voltage-controlled crystal oscillator(VCXO).The system controls the DAC to output avoltage signal acting on the voltage controlled crystal oscillator through the relationship between the voltage of the voltage controlled terminal of the voltage controlled crystal oscillator and the output frequency,and locks the output frequency of the voltage controlled crystal oscillator to the reference signal.In the phase-locked loop system designed in this paper,the reasonable use of the group phase quantum effectively improves the phase-detection accuracy;the signal containing the phase difference information is directly obtained by the ADC quantization,and the original phase difference condition is maintained well;the introduction of digital technology helps to achieve high precision measurement and control.The experimental results show that the phase-locked loop system designed in this paper can realize phase-locked control between arbitrary frequency signals.The accuracy of the locked frequency source can reach 9E-12,which also improves the frequency stability of the frequency source.It has a simple structure and flexible application,and it is of great significance for improving the performance of the time-frequency standard device.