Carrier and symbol timing synchronization method under low signal-to-noise ratio condition

Abstract

The invention belongs to the technical field of digital communication, and particularly relates to a carrier and symbol timing synchronization method. The carrier wave and symbol timing synchronization method under the low signal-to-noise ratio condition comprises the steps that a receiving end carries out quadrature demodulation on received signals to generate two paths of baseband signals, pilotfrequency phases and fractional delay are synchronously obtained through a numerical control oscillator of a symbol timing loop, phase discrimination is carried out on the baseband signals through the pilot frequency phases, carrier wave phases are extracted, and carrier wave synchronization is completed, fractional interpolation is carried out by using fractional time delay to obtain two paths of symbol information, phase ambiguity recovery is carried out on the two paths of symbol information, and the two paths of symbol information are converted into output signals. According to the method, two implementation loops of carrier synchronization and symbol timing synchronization are combined, the pilot frequency information ingeniously extracted by the symbol timing loop is utilized to realize carrier synchronization, the problem of phase ambiguity is solved, and the complexity and the implementation error of demodulation implementation are reduced.

Description

technical field [0001] The invention belongs to the technical field of digital communication, and in particular relates to a carrier and symbol timing synchronization method. Background technique [0002] In a digital communication system, synchronization is an essential link. It mainly restores the original information bits from the received signal, and uses these parameters to achieve the purpose of demodulation. [0003] Since the carrier wave at the transmitting end in the digital communication system cannot be exactly the same as the local oscillator at the receiving end, and the signal has fast fading changes during transmission, the center frequency of the transmitted signal deviates from zero, resulting in a frequency offset problem at the receiving end. The phase of the signal transmitted through the channel will also be affected by the Doppler effect, resulting in phase jitter in the signal. The carrier frequency offset is shown as the rotation of symbol points on...

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Problems solved by technology

[0006] The present invention aims at using the method of pilot frequency insertion to realize carrier and symbol timing recovery, but the carrier synchronization convergence is unstable and there are large fluctuations, which affects the technical problem of demodulation performance, and the purpose is to provide a download wave and symbol timing under the condition of low signal-to-noise ratio synchronization method

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