Experience of working out and modernization of multibeam echosounders

Summary form only given, substantially as follows:- The primary aim of multibeam sonar is to develop the device for direct measurement of bottom reverberation to study regions with different seafloor morphology. This task determines the configuration and processing method of the device installation on towed body for measuring near the bottom, using of nonequidistant array for diminishing the number of independent receiving channels, simultaneous beamforming in the vertical plane parallel to direction of towing, statistical signal processing. The beamforming in receiving antenna included Fourier-transform of signal spatial correlation function (FT) calculation; the correlation function's estimation was the result of averaging of sound pulses. It was experimentally established that for definite relations between vessel's speed and ocean depth the averaging doesn't lead to sufficient diminishing of spatial resolution if spatial correlation function converges rapidly, and mentioned way of beamforming may be used for bathymetric measurements. The experience in working out of towed multibeam sonars was used for restoration of multibeam echosounder ECHOS-XD installed at RN "Akademik Ioffe" in 1988. The receiving and transmitting matrices, power amplifier and multichannel receiving amplifier of this echosounder were in working state, but beamformer and processing system for depth measuring were ruined. The main idea of echosounder's modernization was to incorporate the new system of beamforming and control into existing matrices and amplifiers. It was possible because the transmitter and multichannel receiving amplifier are practically autonomous with simple digital control interface; the control was fulfilled by standard personal computer through the plate of universal parallel port ADVANTECH PCL-720. The method of signal bringing into computer included synchronous detecting from 14 independent channels, simultaneous remembering of instant values of 28 quadrature components in sample-and-hold tracks with discretisation frequency 1 kHz, sequent reading by ADC.