A kind of automatic frequency correction method and system

Abstract

The invention discloses an automatic frequency correction method which comprises the following steps: S1. carrying out down-conversion decimation filtration on a received and sampled digital signal of with the frequency point is 15.36 MHz and the data rate is 61.44 MHz to obtain a 269.473K GSM (Global System for Mobile Communication) signal; S2 carrying out FCCH (frequency correction channel) detection on the GSM signal to acquire an FCCH signal; S3. fitting FCCH data into a linear slope, and demodulating to obtain an output slope; S4. comparing the output slope with the ideal slope to calculate a slope deviation value so as to correspondingly obtain a frequency deviation value; acquiring input data of a synchronous control circuit according to the slope deviation value through a look-up table, and allocating the input data to the synchronous control circuit; and S5. generating an output voltage by the synchronous control circuit according to the input data to control the crystal oscillator clock pulse (CP), thereby implementing the frequency correction. The invention also discloses an automatic frequency correction system.

Description

technical field [0001] The invention relates to an automatic frequency correction method and system. Background technique [0002] In a wireless communication system, in order to ensure normal communication between transceiver wireless stations, it is necessary to ensure that the frequency of the frequency source signal at the receiving end is consistent with the frequency of the frequency source signal at the transmitting end, so as to achieve the purpose of synchronization and correctly demodulate the signal transmitted by the user. [0003] In order to achieve synchronization, conventional digital wireless stations use high-precision crystal oscillators at both ends of the transceiver, which are expensive. At the same time, frequency drift will occur after long-term use, and frequency deviation will occur at both ends of the transceiver, which requires regular manual frequency adjustment. Correction, for some wireless stations using cheap crystal oscillators, their stabil...

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Problems solved by technology

[0003] In order to achieve synchronization, conventional digital wireless stations use high-precision crystal oscillators at both ends of the transceiver, which are expensive. At the same time, frequency drift will occur after long-term use, and frequency deviation will occur at both ends of the transceiver, which requires regular manual frequency adjustment. Correction, for some wireless stations using cheap crystal oscillators, their stability will decrease due to a long time, which will add a frequency offset to the received data, which will cause frequency offsets in the near and far-end system frequencies, and the far-end will not Demodulation of the signal at the near end, so that the near and far ends cannot be synchronized

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