A Spread Spectrum System Based on Variable Length Composite Orthogonal Codes

Abstract

The invention discloses a spread spectrum system base on a length-variable compound orthogonal code. The system comprises an emitter and a receiver; the emitter comprises a coding spread spectrum unit, a modulation unit and a synchronous pseudo code unit at least; and the receiver comprises a despreading and demodulation unit and a synchronous pseudo code capturing and tracking unit at least. The coding spread spectrum unit adds a synchronous-path pseudo code signal to a data-path signal used for sending to obtain a combination signal, and sends the combination signal to the modulation unit; and the modulation unit sends a modulated combination signal to the receiver for despreading. Via technical schemes of the invention, it is ensured that the spread spectrum communication system is higher in anti-interference performance, high in transmission speed and lower in occupation rate of the bandwidth resource.

Description

technical field [0001] The present invention relates to a spread spectrum communication system, in particular to a spread spectrum system based on variable length compound orthogonal codes. Background technique [0002] Spread spectrum communication is the abbreviation of spread spectrum communication, that is, through spread spectrum modulation, a higher frequency pseudo-random code broadband signal is used to spread the spectrum, so that it occupies far more than the minimum bandwidth necessary for the information to be transmitted. Spread spectrum communication was early used in military communication. Spread spectrum communication has a unique set of advantages due to the fact that the bandwidth used to transmit the information is much greater than the bandwidth used by the information itself. Spread spectrum communication is especially suitable for the military field, with low probability of interception and anti-jamming characteristics. Spread spectrum communication ...

AI Technical Summary

Problems solved by technology

[0008] (2) The power density of the broadband spread spectrum communication signal is very low, and it is difficult to identify it when it is buried in the noise signal

For the spread spectrum communication system itself, it can communicate normally under a high noise background and low signal power density. Even if it is intercepted, it is quite difficult to detect the spread spectrum signal in a wide frequency band.

[0009] (3) General intentional jamming and man-made jamming are narrowband tracking and aiming jamming, which have little effect on wideband spread spectrum communication systems

[0010] (4) Due to the correlation detection of the spread spectrum pseudo-random code at the receiving end, even if the spread spectrum signal of the same frequency is used for interference, due to the correlation between different code sequences, the interference is difficult to be effective

However, spread spectrum communication also has the following disadvantages: although the spread spectrum communication system has the above advantages, it also pays the price of occupying the frequency bandwidth. a big disadvantage for precious wireless communications

[0024] The above-mentioned existing commonly used spread spectrum systems have their own advantages and disadvantages. The main problem is that while the anti-interference ability is improved, the bandwidth of signal transmission is greatly increased, and the increase is from dozens of times to thousands of times.

In addition, the uplink of civil CDMA also adopts multi-ary spread spectrum technology. Although it saves frequency band occupation, it has problems such as long time for synchronous acquisition, need for feedback information and complex circuit implementation, and is not suitable for military anti-jamming communication.

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