Local Strong Interference Suppression Technology Research

In recent years, with the progress of science and technology, underwater acousticinerference, one important branch of acoustic warfare, is developing rapidly, and is graduallyconverting from early passivity to intelligence. Intelligent acoustic jamming equipment has toscout the target while launching interference signal, so that it can deal with the change oftarget’s signal form in time. Thus jamming equipment should be able to fight against localstrong interference to get enough detective signal-to-noise ratio. Around the technology ofrestraining the local acoustic interference, this paper first introduces the characteristics andthe difficulties of the technology, then proposes methods of restraining the local acousticinterference through3approaches.(1) the use of vector sensor’s directivity to suppress multipath interferenceIt first briefly introduces the vector sensor’s working principle, characteristics, and itsrestraining principle to all kinds of interference. Then it proposes a method of suppressing thelocal direct sound and water surface reflection interference by using a two-dimensionalco-vibrating type vector sensor, and introduces its applications.(2) the use of adaptive noise cancellation and adaptive notch filterIt introduces the counteracting principle of adaptive filter, then proposes the adaptivecancellation of noise with the channel compensation. This method can also be applied inadaptive notch filter.(3) the use of time-frequency filter by fractional Fourier transform(FRFT) to suppresssweeping jammingAt first, the definition, properties and advantages in dealing with linear frequencymodulation signals of FRFT are present. Then it introduces the method of time-frequencyfiltering by fraction Fourier transform. At last, it improves this method with the windows ofsmooth edge, so that the side-lobe can be reduced.After these theory analysis of the3approaches, this paper represents the testing andsimulation results. They verifies that the application of vector sensor can increase theisolation of receiving and transmitting, and a notable gain can both be got by adaptive noisecancellation and time-frequency filter by FRFT.