Automatic frequency control method of spread spectrum communication system under condition of large frequency offset

Abstract

The invention relates to an automatic frequency control method of a spread spectrum communication system under the condition of large frequency offset. The carrier frequency offset correction cannot be finished through an automatic frequency control loop under the condition of the large frequency offset by the current method. The method comprises the following steps: firstly respectively and circularly dispreading I / Q chip baseband data after spectrum displacement; implementing delay conjugate cross-product frequency discrimination for adjacent tick data after being circularly dispread; transmitting frequency discrimination output to a digital controlled oscillator through a loop filter and then adjusting the local carrier frequency; and finally utilizing a frequency discrimination result transmitted by the loop filter to analyze variance and judge the convergence state of the loop. With the adoption of the automatic frequency control method of the invention, the carrier frequency offset can be accurately, quickly and reliably corrected, and correction range of the carrier frequency offset is large, and the automatic frequency control method is suitable for the spread spectrum communication system in a quadrature amplitude modulation mode.

Description

technical field [0001] The invention belongs to the technical field of spread spectrum communication, and in particular relates to an automatic frequency control method of a spread spectrum communication receiving system under the condition of large frequency deviation. Background technique [0002] Spread spectrum communication technology has the advantages of anti-jamming, anti-noise, anti-multipath fading, working under low power spectral density, and good confidentiality, so it is widely used in military and civilian communication fields, including mobile communication services of course. In mobile communication services, if the carrier of the transmitting system and / or the receiving system has high mobility, it will cause a large Doppler frequency shift, resulting in too large carrier frequency deviation between the transmitting system and the receiving system, so that it cannot Normal demodulation. Common carrier recovery methods include automatic frequency control (A...

AI Technical Summary

Problems solved by technology

But for some high-speed mobile communication occasions, the system transmitter and receiver carrier are in a relatively high-speed motion state, and the Doppler frequency shift deviation value of the carrier can reach the symbol rate R s , at this time, the conventional automatic frequency control method mentioned above cannot complete the correction of the carrier frequency offset

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