Abstract:  Passive source localization is a crucial issue in underwater acoustics. Conventional matched field processing(MFP)，which takes into account the propagation from source to receivers using pressure field replicas to match the measured signals to obtain the more accurately localization results，therefore it have been regarded as a good localization technique. However, Conventional MFP uses large vertical arrays to locate an underwater acoustic target, which not only increases equipment and computational cost but also subject to some problem such as clement failures and array title. At the same time, the sidclobes of the ambiguity surface of conventional MFP are higher when the number of hydrophones are quite small，which degrade the localization performance. In this paper, a matched field localization algorithm using two-hydrophone for underwater acoustic pulse signal with unknown emitted signal waveform is proposed.The localization algorithm was firstly analyzed from time domain, using the received signal of a single hydrophone and the ocean channel pulse response which can be calculated from an acoustic propagation model，the emitted signal for every grid location over search region can be estimated by employing the least square solution in the time domain.The resulting the estimated signal is then cross convolved with the ocean channel pulse response for various trial source location to generate the replica signal. Finally, matched field localization of using two-hydrophone for underwater acoustic pulse signal with unknown emitted signal waveform can be realized by comparing the difference between the received signal and the replica signal of a single hydrophone to construct the localization error function
yielding the ambiguity surface of localization function.Theoretical analysis and numerical simulation results from a shallow-water environment for broadband pulse signals demonstrate the proposed matched field localization algorithm require no priori knowledge of the source signal waveform and the ambiguity
surface has a sharp peak and low sidclobes and has significant localization performance.