| Direct sequence spread spectrum(DSSS)technology is widely used in military and civilian fields due to its strong anti-interference ability,low probability of interception and good confidentiality.And it presents a tough challenge to communication countermeasures just because the features above.In order to overcome the spread spectrum gain,the traditional interference must obtain better interference effect at the expense of higher power.Although interference with the same system requires low power to get effective result,as long as greater than the signal,its implementation conditions are extremely harsh.The interference signal must be completely synchronized with the received signal,so the interference effect is greatly affected by the delay.Therefore,it is very crucial to study how to interfere DSSS communication system effectively at a lower power cost.According to the idea of smart jamming to interfere the part that must be interrupted in the communication system,and synchronization is the prerequisite for normal communication and the basis of demodulating signals,it's necessary to study the interference response for synchronization and the effectiveness of the interference for pilot.In this paper,aiming at the effective interference for DSSS communication system,mainly focusing on the interference performance of pilot,the interference response to carrier synchronization and bit synchronization is analyzed,and a new method based on smart jamming to interfere pilot is proposed in DSSS communication system.First of all,according to the principle of DSSS communication system,a communication system model based on MATLAB simulation platform is built to verify the bit error rate.Then,carrier synchronization theory and design method is introduced as a preparation for the next step.And the interference response of noise FM jamming,chirp jamming and the same system jamming to the carrier synchronization loop is deeply analyzed through the mathematical model.The influence of the three kinds of interference on the carrier tracking waveform is showed in the experimental results.Then,the mathematical model of the jamming output response is analyzed according to the principle of bit synchronization module in DSSS communication system.And the advantages brought by the interference to bit synchronization is analyzed from the aspects of synchronizationprobability and bit error rate.Finally,the idea of smart jamming is used on the important pilot data on which synchronization relys to work.The simulation of the pilot data is carried out to verify the feasibility,effectiveness and superiority of the interference in the synchronization section of DSSS communication system.And this method can save interference power compared with the conventional interference idea on the condition of getting equal even better interference effect. |
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