G.L. Chernihovskaja

The particularities of searching for small-zized objects by means of sonar are considered. These objects can be «black boxes» of flying machines, a tumbled seaborne heads of the ballistic rockets, containers with hazmats, particularly - unauthorized hidden keeping them, bottom mines, sunk torpedoes. It Is Shown that for finding such objects, on the one hand, necessary to provide the high range resolution of sonar signals that corresponds to the expansion of their spectrum. On the other hand, when sonar signal is spreading into soil, frequency dependent absorption of the energy of the acoustic waves occurs, moreover degree of the absorption raise with increasing of the frequency.So reasonable reduce the central signal frequency that at conservation of the high range resolution brings about need of the use ultra wideband (UWB) signals. The relationship between object length and spectrum parameters of the radiated UWB signal  its width and upper and lower border frequency- is installed. The choice of the square-law interval of correlations as measures of the signal range resolution is motivated. The influence of the signal energy absorption in the soil on square-law interval of the correlations and, accordingly, on range resolution is explored. Graphs of the dependencies of the range resolution are received for standard UWB signals from depth of the submersion of the object in soil. As such signal are chose class signal with square-wave spectrum, to which possible refer the complex signals, for instance, LFM signals at high index of modulations, and UWB radio impulses with one or more period of the fluctuations of the central frequency. It Is Shown that UWB echo signal range resolution grows worse with increase passed in soil of the distance that quicker, than broader radiated signals spectrum. Under greater depth for UWB signals of any form potentially attainable range resolution practically does not depend on widths of the energy signals spectrum, can be determined from asymptotic approach and constitutes a units of the percent from depth of the submersion of the object in soil. The Got results can be useful at determination of range of the finding hydrolocation station in step of her designing and for development of the engineering methods of the calculation her main features.