A carrier frequency offset estimation method of a baseband signal and a device thereof

Abstract

A carrier frequency offset estimation method of baseband signal and device thereof, the carrier frequency offset estimation method comprises the steps of baseband signal acquisition, complex signal calculation, complex signal frequency spectrum shifting, complex signal resampling, useful spectrum line frequency point sequence number acquisition and carrier frequency offset estimation, etc. As thecomplex signal after spectrum shifting is resampled, the sampling rate of the system can be matched to a fixed value, so that FFT processing with a fixed number of points can be adopted to obtain a spectral sequence including useful spectral lines, so that the system can obtain the frequency point number corresponding to the useful spectral line without increasing the number of FFT points, but also simplifies the calculation process of obtaining the frequency point serial number. On the premise of guaranteeing the higher precision of carrier frequency offset estimation, it can speed up the processing speed, further reduce the calculation time and the running cost of the system, and finally help to improve the real-time performance of OQPSK signal in demodulation processing and carrier frequency offset estimation processing.

Description

technical field [0001] The present invention relates to the communication field, in particular to a carrier frequency offset estimation method and device for a baseband signal. Background technique [0002] In the field of modern communication, QPSK (Quadrature Phase Shift Keyin, Quadrature Phase Shift Keying) is a very important modulation method. In the QPSK signal modulation process, when the code group is 0011 or 0110, a 180° carrier phase jump is generated. This phase jump will cause envelope fluctuations. After passing through the nonlinear components, the filtered out-of-band The components are recovered again, causing spectrum expansion and increasing interference to adjacent channels. In order to eliminate the 180° phase jump, OQPSK (Offset-QPSK, offset quadrature phase shift keying) was developed on the basis of QPSK; OQPSK is a constant envelope digital modulation technology, which combines the in-phase and quadrature The code streams of the branches are stagger...

AI Technical Summary

Problems solved by technology

However, reducing the number of FFT points (that is, increasing the frequency resolution f r value) is the inaccuracy of the estimated value of carrier frequency offset, which will have an adverse effect on the final demodulation result. This method is mostly used in the case of large frequency offset to achieve a rough It is estimated that the estimation accuracy is generally above 1kHz

[0010] (2) Loss of lock may occur when the carrier frequency offset estimation error is large

In the case of using the Costas loop to realize carrier estimation and locking, because the Costas loop is a closed-loop system, it is more complicated to implement, and the locking time is related to the carrier frequency offset. The larger the frequency offset, the longer the locking time. When the carrier frequency Loss of lock often occurs when the bias is too large

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