Digital communication frequency deviation eliminating method and device using the same

Abstract

The present invention discloses a method for eliminating digital communication frequency deviations and a device using the method. The device for eliminating digital communication frequency deviations firstly carries out coherent demodulation to RF signals, tracks phase positions of two paths of demodulated I / Q frequency deviation signals to determine to output an effective path of signal as compared with a pre-set range [M, N]; and outputs the signal after polarity selection to the obtained effective signals according to whether the polarities of the two paths of demodulated I / Q signals are the same. The method for eliminating digital communication frequency deviations can dynamically track the phase position of the two paths of the I / Q signals, promptly switch the signals onto the effective signals, and compensate whether the signal polarity is turned over in real time according to a relation between the phase position and the polarity and output restored correct effect signals as frequency deviations exist between a local clock source and a transmitting clock source for coherent demodulation, in particular drastic frequency deviations. Certainly, the present invention is also suitable for eliminating different transmission and receiving clock sources caused by other reasons in the field of communication.

Description

technical field [0001] The invention relates to the field of digital communication, more specifically, to a method for eliminating frequency offset in digital communication and a device using the method. Background technique [0002] In the field of digital communication, demodulation methods can basically be divided into two categories, namely coherent demodulation and non-coherent demodulation. The former is to extract the modulation signal from the phase information of the modulated wave, and the latter is to extract them from the amplitude information of the modulated wave. Because coherent demodulation requires the receiver to provide a local reference carrier that is synchronized with the carrier frequency, it can also be called synchronous demodulation. When coherent demodulation is used, the local oscillator at the receiving end needs to be at the same frequency as the carrier frequency of the sending signal. If there is a frequency deviation, the receiving end wil...

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Problems solved by technology

When the frequency difference is large, the applicability of this method is very poor: for example, when the frequency difference is 100Hz, the effective communication time without signal phase reversal is 2.5ms

If the frequency difference is large, such as 10KHz, the effective communication time without signal phase reversal is 25us. If the communication time is greater than 25us, the phase reversal of the demodulated baseband signal will occur, causing demodulation errors.

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