Fast fourier transform (FFT) carrier frequency estimation and Costas loop based non-cooperative communication carrier synchronization system

Abstract

The invention discloses a fast fourier transform (FFT) carrier frequency estimation and Costas loop based non-cooperative communication carrier synchronization system. The system comprises two parts, namely, an FFT carrier frequency estimation module at the front end and a Costas loop carrier synchronization module at the rear end. According a working principle, an input signal simultaneously acts on the two modules; the FFT carrier frequency estimation module firstly performs carrier frequency estimation on the input signal, and an enabling end of the Costas loop is valid till the FFT carrier frequency estimation module transmits estimated carrier frequency to the Costas loop; the carrier frequency is transmitted to a numerically controlled oscillator (NCO) in the Costas loop carrier synchronization module by using an estimation value of the carrier frequency as an initial oscillation frequency; the oscillation frequency of the NCO is controlled, and high-precision carrier synchronization is performed on the input signal; and after capture of the input signal is finished, the NCO outputs a precise carrier extraction signal. According to the system, capture time is shortened, and capture bandwidth is increased indirectly, so that carrier synchronization of an unknown signal in non-cooperative communication is completed.

Description

technical field [0001] The present invention relates to the technical field of digital communication, in particular to a communication carrier synchronization system. Background technique [0002] In the communication system, synchronization is a very important issue. The synchronization circuit is an indispensable and important part of the receiver and a necessary guarantee for normal communication. In the entire synchronization system, there is no transmission of useful information, but only after the synchronization between the receiving end and the sending end is established, the two parties can start normal information transmission, that is, the receiving end can normally receive the information sent by the sending end , so as to achieve the purpose of communication, so synchronization is the premise of information transmission. The performance of the synchronization system will directly affect the performance of the communication system. If the required synchronizatio...

AI Technical Summary

Problems solved by technology

[0006] However, when the initial frequency offset is relatively large, the acquisition time of the Costa loop is longer

When the initial frequency difference exceeds a certain range, the Costas ring cannot even achieve carrier synchronization

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