Costas Sequence Synchronization via All-Phase Spectrum Correction
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Solution Overview
Problem
The short-wave MFSK communication time-frequency synchronization algorithm based on the Costas sequence faces limitations in accuracy due to spectrum leakage and noise interference, leading to large errors in frequency and time synchronization, especially when frequency offset is an integer multiple of the spectrum resolution and when time delay is present.
Innovation Solution
A time-frequency joint synchronization method using an all-phase spectrum-corrected Costas sequence, which involves dividing the time-domain signal, performing all-phase Fourier transform, and iterative correction of frequency and time delay errors to improve synchronization accuracy by reducing spectrum leakage and mutual interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete spectrum analysis algorithm is used to improve frequency estimation accuracy, then frequency estimation accuracy is improved, but large errors occur when frequency offset is an integer multiple of spectrum resolution
Solution Approach 1:
The patent introduces an all-phase spectrum as an intermediary between the original spectrum and the final frequency estimation. The all-phase spectrum is constructed using both magnitude and phase information, and serves as a mediator to correct the discrete spectrum. This intermediary allows the system to avoid the integer multiple frequency offset error by using the corrected spectrum for gravity-center calculation, thereby resolving the contradiction between improved accuracy and maintained reliability.
Solution Approach 2:
The patent changes the parameter representation by constructing an all-phase spectrum that incorporates both magnitude and phase parameters. Instead of relying solely on the traditional magnitude spectrum, the system transforms the spectral parameters to include phase information, which helps in correcting the frequency estimation and avoiding the integer multiple offset error. This parameter transformation resolves the contradiction by providing more comprehensive spectral information.
2Measurement precision
If window function step length is changed to improve time synchronization accuracy, then time synchronization accuracy is improved, but spectrum leakage and mutual interference increase
Solution Approach 1:
The all-phase spectrum acts as an intermediary that corrects the spectral information affected by spectrum leakage. By constructing the all-phase spectrum with both magnitude and phase components, the system can identify and correct the leakage effects. This intermediary approach allows the use of smaller window step lengths for improved time synchronization while the all-phase spectrum correction compensates for the increased spectrum leakage, thereby resolving the contradiction.
3Measurement precision
If iterative correction is performed to improve synchronization accuracy, then synchronization accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent implements a feedback mechanism through iterative correction, where the all-phase spectrum correction results are fed back to improve the frequency and time offset estimates. The iteration process continuously refines the synchronization parameters by using the corrected spectrum information. This feedback approach resolves the contradiction by providing a systematic method to improve accuracy through controlled iterations, where the computational complexity is managed by the convergence properties of the feedback loop.
Data Source
AI summary
The present invention relates to the field of digital signal processing, and in particular to a Costas sequence time-frequency joint synchronization method based on all-phase spectrum correction. The method improves the defects existing in a discrete frequency spectrum correction algorithm using short-time Fourier transform and sliding correlation. The improvement mainly comprises: the present disclosure provides a solution based on iterative optimization: when an actual frequency offset is an integral multiple of the spectral resolution, a large error can occur, frequency offset correction and time delay correction are carried out on a signal by using an estimated value having a large estimated error, then estimation is carried out again, and the frequency offset of the signal is not a special value by means of an iteration mode.