Non-data aided OQPSK (Offset Quadra Phase Shift Keying) signal closed loop carrier synchronization method

Abstract

The invention provides a non-data aided OQPSK (Offset Quadra Phase Shift Keying) signal closed loop carrier synchronization method. The square spectrum characteristics of an OQPSK signal are utilized, a square spectrum estimation based carrier frequency offset coarse estimation algorithm is adopted, and accordingly the range of the frequency of the signal can be effectively reduced. A carrier synchronization loop is of a dot product and cross product frequency discriminator and phase discriminator combined cross ring structure and accordingly the speed and the accuracy of the carrier synchronization can be ensured simultaneously. A proportional integral filter is adopted as a loop filter to enable the synchronization loop to be a second-order loop and accordingly the stable loop dynamic response can be implemented under the conditions that the direct current gain is infinite and the frequency offset is a constant. According to the non-data aided OQPSK signal closed loop carrier synchronization method, the frequency offset can be accurately estimated, the accuracy and the speed of the carrier synchronization can be ensured, and the recruitments of a communication system can be met through the combined utilization of a dot product and cross product frequency discriminator and phase discriminator on the basis of the square spectrum frequency offset coarse estimation.

Description

technical field [0001] The invention belongs to the technical field of testing, and in particular relates to a non-data-assisted OQPSK signal closed-loop carrier synchronization method. Background technique [0002] As a constant envelope digital modulation technology, OQPSK not only has high frequency band utilization and power utilization, but also eliminates the 180° carrier phase jump. In the actual communication system with limited bandwidth, the envelope fluctuation is small and has been It has become a commonly used modulation method in the field of measurement, control and communication, such as TDMA and CDMA systems. [0003] Since many communication systems use coherent demodulation to restore the modulated signal, the receiver needs to generate a carrier signal with the same frequency and phase relationship as the signal transmitted by the transmitter when performing coherent demodulation. Therefore, in order to realize the correct transmission of the signal and ...

AI Technical Summary

Problems solved by technology

The lock-in time of the carrier synchronization loop is significantly affected by the carrier frequency offset: when the frequency offset is small, the phase-locked loop can be locked quickly; when the frequency offset is large, the lock-in time required by the phase-locked loop is longer ; When the frequency offset is too large, the phase-locked loop may even lose lock

In the actual communication system, the frequency deviation range of the signal is often large, and the pure carrier synchronization algorithm based on the phase-locked loop cannot meet the processing requirements of the actual system.

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