Research On Suppression Of Narrow Band Jammer In DSSS Based On Wavelet Transform

The communication system of direct-sequence spread-spectrum (DS/SS) has the ability of restraining the interference that intended or not using spread-spectrum plus. but the resource of frequency is limited ,system can't depend on increasing the spread-spectrum plus to control the jam only when encounter big power disturb .Using the technology of signal dispose to improve the system's ability of resisting interfere, when huge jam appear especially strong antagonize environment of military appliance area .The conventional wavelet transform resist narrow band interfere established on the spectrum of direct spread is white spectrum. But in the actual spread system ,because the complexity of receive machinery and the channel's bandwidth is limited, the spread serial's period can't too long, or else it can lead phenomenon of the spectrum's color, that is the difference of every frequency area's power consistency is very big .At the same time system is likely to change the period of spread serial ,which make the spectrum of direct spread signal in actual channel isn't white spectrum .In this case if we use same threshold in every frequency area is not suitable ,it may affect the system's capability of resisting narrow band jam.In order to recuperate the influence to the system that using immovable threshold to resist narrow band jam based on wavelet transform .This paper combine WPT and AET (adaptive energy threshold) to wipe off jam, enact the threshold of every frequency area based on the power of direct spread signal. Make sure the threshold of every frequency area and the power of direct spread signal has the relation of linearity to improve the system's ability of resisting narrow band jam.Through the demonstrate of theoretic and simulation we prove that in the case of the same decomposed, suppression of narrowband jamming using wavelet transform with adaptive energy threshold in DSSS boost the performance of the system in 4dB. meanwhile with the increased number of decomposed ,in the case of suppression of narrowband jamming using wavelet transform with adaptive energy threshold in DSSS ,its performance of suppression upgrade greatly compared with immovable threshold to resist narrow band jam based on wavelet transform.