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

A technology of automatic frequency control and spread spectrum communication, applied in the field of spread spectrum communication, can solve the problem of inability to complete the correction of the carrier frequency offset, and achieve the effect of a large carrier frequency offset range.

Inactive Publication Date: 2012-09-26
海宁鼎丞智能设备有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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 of the carrier can reach the symbol rate , at this time, the conventional automatic frequency control method mentioned above cannot complete the correction of the carrier frequency offset

Method used

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

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Experimental program
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Effect test

Embodiment Construction

[0021] Step (1) After orthogonal demodulation, the chip data of the quasi-baseband preamble sequence symbols that still have residual frequency difference after the spectrum shift is completed To despread, calculate and ,in is the I / Q channel spreading code sequence generated locally by the receiver.

[0022] Step (2) after a chip interval clock ,calculate

[0023]

[0024]

[0025] That is, the sliding window method is used to select N At the same time, the locally generated spreading code sequence is cyclically shifted, and then the despreading operation is performed to obtain the new despreading symbol data I(m+1) and Q(m+1) .

[0026] Step (3) calculation

[0027]

[0028]

[0029] Repeat step (1) and step (2), each chip clock will generate a frequency discrimination output u3 .

[0030] Step (4) calculation

[0031]

[0032] in accordance with value, correct the local carrier frequency of the digitally controlled...

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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...

Claims

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Application Information

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IPC IPC(8): H04B1/7073
Inventor 易志强张福洪戴绍港李芸
Owner 海宁鼎丞智能设备有限公司
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