QPSK baseband recovery system resistant to large frequency offset

Abstract

The invention proposes a QPSK baseband recovery system resistant to a large frequency offset, and is used for solving the technical problem that a carrier is locked slowly or cannot be locked when thefrequency offset of an existing system is large. The QPSK baseband recovery system comprises a data sampling module, a carrier rate pre-estimation module, a switch selection module, a low-speed baseband recovery module, a carrier locking detection module, a high-speed baseband recovery module and a timing synchronization judgment output module; the data sampling module receives and samples a modulation signal; the carrier rate pre-estimation module roughly estimates the modulation signal carrier frequency; the low-speed baseband recovery module based on a closed loop and the high-speed baseband recovery module based on an open loop perform baseband data recovery on the sampled data under the control of the switch selection module; the carrier locking detection module detects whether a local carrier of the low-speed baseband recovery module is locked or not; and the timing synchronization decision output module performs timing synchronization and hard decision on the recovered basebanddata to obtain final demodulation data. According to the QPSK baseband recovery system resistant to the large frequency offset provided by the invention, the baseband recovery speed is high and the bit error rate is low.

Description

Technical field [0001] The present invention belongs to the technical field of digital communication, and relates to a QPSK baseband recovery system, in particular to a QPSK baseband recovery system against large frequency deviation, which can be used in a QPSK modulation and demodulation system. technical background [0002] Digital communication technology has become the mainstream of contemporary communication technology. In digital communication systems, digital modulation and demodulation is an indispensable part and an important means of communication signal transmission technology. [0003] Digital modulation is a process that uses digital signal processing to load useful baseband signals onto a higher frequency carrier signal. Digital demodulation is the inverse process of digital modulation. It uses digital signal processing to extract the original useful baseband signal from the modulated signal. The digital modulation methods include amplitude keying (ASK) and frequency ...

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Problems solved by technology

[0006] The purpose of the present invention is to overcome the above-mentioned defects in the prior art, and propose a QPSK baseband recovery system that resists large frequency offsets, which elim

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