B.I. Filippov – Ph.D.(Eng.), Associate Professor, Department «Information Security», Novosibirsk State Technical University E-mail: Fillippov-boris@rambler.ru

A.O. Kozhaeva – Student, Department «Information Security», Novosibirsk State Technical University E-mail: Anya.Kozhaeva@yandex.ru

Determination of inclined distance R to a source of acoustic signals in hydroacoustic systems of navigation based on measurement of time of distribution τR of a signal between a source of an acoustic signal and the vessel. The radiation of acoustic signal a source can be carried out or on the specified program, then the source of a signal performs the functions of a beacon, or as a result of receiving a request signal from the vessel. In this case, the information acoustic signal plays the role of a beacon – responder. In both methods the error of determination of inclined distance between the navigation acoustic signal (NAS) and the vessel ∆R depends on an error of a task of average value of speed of sound c and an error of measurement of time of distribution of an acoustic signal between them ∆τR. Precision quartz generators have to be used to creation of the setting generators of the underwater apparatus (UA) and the docking module (DM) at realization of a method of determination of inclined distance based on a binding to a common time scale in the creating equipment of the high-frequency hydroacoustic system of transformation (EHST). For precision quartz generators the long-term relative instability is fp( )t  f0  2 10 10 , that is connected with considerable material costs. The advantage of the method of measurement on the system "request-answer" is the possibility of using simpler and cheaper setting generators and in the exception at the stage of preparation of the UA to work labor-consuming procedure transformation frequencies setting generators compared with the method of measurement based on a binding to a common time scale, with other things being equal. 

Signals with a large base used as navigation in combination with their reception "as a whole" allows to increase accuracy of measurement of time of distribution of an acoustic signal between UA and DM τR. Phase-shift keyed signals based on M– sequences used as navigation signals allow to get winning in the accuracy of the moment of detection of a signal by the receiver in n of times in comparison with use of impulse signals where n – number of symbols in the M-sequence. Reception of the synchronous signal R(t) is carried out using suboptimal receiver. 

In work the required value of the relation signal/noise on an entrance of the receiver h2 has been determined at measurement of time of distribution of acoustic navigation signals between UA and DM by the "request - answer" system. The value of step of the correction of position of output impulses of the system of clock synchronization is chosen at the level of 1% from duration T0 of symbol, at the construction of equipment of EHST on the system "query - answer" and at relations a signal/noise h2 ≤ 20 dB provides winning in exactness of moment of detection a signal, consequently, and inclined distance in 6…8 times.

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