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Costas sequence time-frequency joint synchronization method based on all-phase frequency spectrum correction

An all-phase spectrum, time-frequency combined technology, applied in synchronization device, synchronization error detection, frequency modulation carrier system, etc., can solve the problem of error, main lobe spectral line interference, etc.

Active Publication Date: 2021-05-07
CHONGQING UNIV OF POSTS & TELECOMM
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Problems solved by technology

If there is a time delay in the signal, the sampled signal will have a noise-only signal. In this case, using a window function whose length is a single symbol time for the short-time Fourier transform will result in a part of the current symbol The information exists in the next symbol time. In the MFSK signal, when the frequency interval between two symbols is small, due to the influence of spectrum leakage, it will cause serious interference to the main lobe spectral line used by the discrete spectrum analysis algorithm. cause large error
[0006] In summary, although the time-frequency joint synchronization algorithm for shortwave MFSK communication based on Costas sequences has high estimation accuracy, there is still room for improvement. The improvement of the spectrum correction algorithm will further improve the synchronization accuracy of the algorithm

Method used

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  • Costas sequence time-frequency joint synchronization method based on all-phase frequency spectrum correction
  • Costas sequence time-frequency joint synchronization method based on all-phase frequency spectrum correction
  • Costas sequence time-frequency joint synchronization method based on all-phase frequency spectrum correction

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Embodiment 1

[0033] This embodiment provides a Costas sequence time-frequency joint synchronization method based on full-phase spectrum correction, such as Figure 1-2 Shown, in a preferred embodiment, it comprises the following steps:

[0034] Step S1, after receiving the time-domain signal x(N), the receiving end divides the time-domain signal x(N) according to the symbol time, and changes the time-domain signal x(N) into m times representing symbol information Domain signal, get the split signal as x 1 (n), x 2 (n)...x m (n), referred to as the split signal x i (n), where i=1, 2, ..., m, m represents the number of divided signals.

[0035] Step S2, put x i (n) Carry out inversion transform and add window to perform all-phase Fourier transform, and obtain the split signal x after completing the apFFT process i The all-phase Fourier transform of (n) X 1 (W)--X m (W), perform modulus calculation to obtain the segmentation signal x i Spectrum of (n)|X1 (W)| 2 --|X m (W)| 2 , use...

Embodiment 2

[0050] In this embodiment, it is assumed that the symbol time is T, the sampling rate is fs, the time-domain signal frequency offset is f, and the time delay is τ.

[0051] A Costas sequence time-frequency joint synchronization method based on all-phase spectrum correction, including but not limited to the following steps:

[0052] (1), the time domain signal is divided according to the symbol time T, and the divided signal is x 1 (n), x 2 (n)...x m (n). Due to the influence of time delay, part of the information of the previous symbol will exist in the next segmented signal. with x 2 (n) as an example, if there is no time delay, then x 2 (n) represents the time-domain waveform of the second symbol symbol, at this time x 2 (n) is:

[0053] x 2 (n)=A 2 sin[2πf 2 (n-τ)] (1)

[0054] Among them, A 1 Indicates the signal amplitude within the first symbol time, A 2 Indicates the signal amplitude within the second symbol time, n is the time discrete representation, τ i...

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Abstract

The invention relates to the field of digital signal processing, in particular to a Costas sequence time-frequency joint synchronization method based on all-phase frequency spectrum correction, which solves the problems existing in a discrete frequency spectrum correction algorithm using short-time Fourier transform and sliding correlation. The improvement mainly comprises the steps that a solution based on iterative optimization is provided, when the actual frequency offset is the integral multiple of the frequency spectrum resolution, large errors can occur, frequency offset correction and time delay correction are carried out on the signal by using an estimated value with the large estimated errors, then estimation is carried out again, and the frequency offset of the signal is not a special value through an iteration mode. In order to solve the problem 2, due to errors caused by spectrum leakage, all-phase Fourier transform is used for replacing FFT in short-time Fourier transform to reduce the spectrum leakage phenomenon as much as possible. The estimation precision of the original algorithm is improved by improving the two points.

Description

technical field [0001] The invention relates to the field of digital signal processing, in particular to a Costas sequence time-frequency joint synchronization method based on all-phase spectrum correction. Background technique [0002] Shortwave MFSK communication is widely used in application scenarios with low rate and minimum guarantee. For a communication system, the premise of receiving a signal is to detect the signal and realize the synchronization of the transmitting and receiving ends. The quality of the synchronization performance directly affects the performance of the communication system. Synchronization errors or loss of synchronization can result in degraded communication system performance or loss of communication. [0003] In the short-wave MFSK communication system, the commonly used signal synchronization method is a data-assisted synchronization algorithm. The data-assisted synchronization algorithm is completed by inserting the training sequence in th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/10H04L27/00H04L7/00
CPCH04L27/106H04L27/0014H04L7/0054H04L2027/0026H04L7/007Y02D30/70
Inventor 李景慧李国军叶昌荣马欢郑广发罗一平王尊立
Owner CHONGQING UNIV OF POSTS & TELECOMM
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