Decision of problem of measurement of phase shift an echo signals for recognition of underwater objects

The staff of the Hydrolocation Laboratory of the Department of Radio Engineering of Novosibirsk State Technical University have worked in the field of the investigation of some problems of short-range hydrolocation and of the design of short-range sonars (SRS) for many years . Such systems are widely applied for work at internal water tracks and shallow sea owing to perspective exploitation of the sea shelf. They are used to solve different problems concerning navigation, examination of the bottom, mapping, digging of the bottom, during building and emergency works on the bottom, etc. A very important role is played by SRS, particularly side-looking sonars (SLS), when various underwater objects (UO), natural or manufactured, probably of small dimensions, sometimes placed under a layer of silt, on the bottom or near it are located and identifying; also, when the bottom ground is examined and its laminated structure is analyzed. A number of algorithms and devices for automatic identification of the UO are designed and developed in the laboratory. Various signs of the echo signals from the objects, particularly pulse structure, pulse length, the estimate of the moments of the random amplitudes, the form of the histograms, shade signal from the UO etc. The traditional methods and devices of location the objects use only the information about the amplitudes of the echo signals or about the amplitude-frequency responses (AFR) of reflection of the UO. Additional information about UO which allows to increase the reliability of their identification one may obtain by using the phase-frequency response (PFR) of reflection or, at least, a phase shift (PS) of the echo signal reflected by an UO