Spatial coherent optical communication high-dynamic carrier capture tracking loop

Abstract

The invention relates to a spatial coherent optical communication high-dynamic carrier capture tracking loop. The carrier capture tracking loop comprises double frequency locked loops and a phase locked loop, wherein a CPAFC (Cross Product Automatic Frequency Control) tracking algorithm and an ODAFC (Overlap Discrete Automatic Frequency Control) tracking algorithm are effectively combined by adopting the double frequency locked loops to perform frequency capture tracking processing; capture tracking can be performed on gradient frequency offset through the CPAFC tracking algorithm, and coarse capture of a large frequency offset can be performed through the ODAFC tracking algorithm; the working states of the two frequency locked loops are controlled according to a locking state; in a stable locking state, capture tracking is performed on gradient frequency by only adopting the CPAFC tracking algorithm; and in a lock losing state and after entrance of the lock losing state, frequency capture tracking is performed by adopting the two frequency locked loops together, so that capture tracking in a large frequency offset range can be realized. Through adoption of the carrier capture tracking loop, the advantages of the two algorithms are combined; the demands of carrier capture tracking processing at different working stages can be met; and stable carrier capture tracking under a high-dynamic condition is realized.

Description

technical field [0001] The invention relates to the field of coherent optical communication digital demodulation, in particular to a space coherent optical communication high dynamic carrier capture and tracking loop. Background technique [0002] In space coherent optical communication, there is a Doppler frequency shift in communication between satellites in different orbits, and the Doppler frequency shift reaches several GHz, which has a serious impact on the entire communication link. Since the local oscillator light wavelength is constant in a coherent optical communication system, when there is a Doppler frequency shift, the signal light frequency will change and be unstable, which will cause the intermediate frequency signal output by coherent detection to drift. This makes it more difficult to realize the frequency tracking of the local oscillator light to the signal light. In the process of coherent optical communication, the Doppler effect causes the frequency di...

AI Technical Summary

Problems solved by technology

In order to meet the high dynamic performance, the PLL must have a relatively wide bandwidth. The increase of the loop bandwidth will add broadband noise. When the noise level increases to exceed the loop threshold, the carrier tracking loop will lose lock.

If the loop bandwidth of the carrier phase-locked loop is not increased, the carrier Doppler frequency shift often exceeds the acquisition band and synchronization band of the phase-locked loop, which cannot guarantee reliable acquisition and tracking of the carrier

[0004] At present, a separate frequency-locked loop and a phase-locked loop are used for carrier capture and tracking. There are contradictions between the capture bandwidth, capture speed and high tracking accuracy and stability. If the loop capture bandwidth is wider and the capture speed is faster, the tracking accuracy will be relatively low. If the value is lower, the stability of the loop will also be poor. In a dynamic environment, it is easy to cause the dynamic loop to lose lock, and it is difficult to meet the requirements of dynamic performance, tracking accuracy and stability performance at the same time.

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