Synchronous Tracking Method for Underwater Communication Based on Symmetric Triangular Frequency Modulation

Abstract

The invention discloses a synchronization tracking method of underwater communication based on symmetric triangular frequency modulation, and relates to underwater acoustic communication. The synchronization tracking method comprises the steps of setting a Chirp carrier structure of the symmetric triangular frequency modulation and regarding a symmetric triangular frequency modulation signal as a synchronization signal; carrying out FRFT for the signal and regarding an FRFT result as receiving-end reference information, wherein the result comprises an optimal order, a position where a peak is and the like; adding a section of wakeup signals at the front section of the synchronization signal before sending the signal; detecting the wakeup signals by a receiving-end program by using an FFT spectrum analytical calculation method; after a reception system is waked up, carrying out FRFT for the received signals; carrying out preliminary advanced synchronization correction for the signals based on the FRFT result; and carrying out precise synchronization tracking for the signals by utilizing a synchronization tracking ring. By utilizing the symmetry of symmetric triangular waves and combining with an FRFT analysis means, preliminary synchronization correction is realized through analysis of migration characteristics of positions of two peaks, and precise synchronization tracking is realized through a difference of the peak values of the two peaks.

Description

technical field [0001] The invention relates to underwater acoustic communication, in particular to a synchronous tracking method for underwater communication based on symmetrical triangular frequency modulation. Background technique [0002] The underwater acoustic channel is a very complex "time, space and frequency" channel, and the waveform of the signal will be distorted after passing through the underwater acoustic channel. The characteristics of high environmental noise, narrow bandwidth, few applicable carrier frequencies, and large transmission delay make underwater acoustic communication one of the most challenging research topics in modern communication technology. Synchronization is the prerequisite for ensuring the correct and reliable transmission of information. The performance of a communication system largely depends on its synchronization performance. In particular, the chirp communication system commonly used in underwater acoustic communication requires ...

AI Technical Summary

Problems solved by technology

However, the Doppler frequency shift will affect the modulation frequency of the received signal, resulting in failure to match the received signal with the local carrier

In addition, the uneven channel frequency characteristics will make it difficult to extract the matched frequency components

Even if Fractional Fourier Transform is used, the offset of the FRFT peak position is the combined effect of signal delay and Doppler frequency shift. If the Doppler frequency shift is not removed, the delay estimation will not be accurate

[0010] 2. The existing Doppler estimation method is complex and poor in real-time

[0012] 3. The peak value is detected by the amplitude threshold value, and the synchronization position is not accurate

[0013] Affected by channel noise and Doppler fluctuations, using a fixed threshold when using fractional Fourier transform to detect peaks will inevitably lead to missed detection or false alarms, resulting in inaccurate synchronization positions

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