Hardware pre-processing for data of SBL underwater prositioning system

The synchro double-pulse signal mode is frequently used in Short Base Line (SBL) underwater positioning system so as to obtain the information of both distence and depth of a target simultaneously. However, this signal mode also brings about ranging indistinctness resulting in a shorter positionning distance much less than that limited by the period of the synchro-signal.
This paper presents a hardware distance-gate data acquiring scheme. It puts the original data sent to the computer in the order of "direct first pulse--depth information pulse (or first pulse reflected by water surface)…" to guarantee the effective positioning distance of the system. It has the advantage of reducing the processing time of the computer to ensure the real-time functioning of the system.
A Fig. of the orbit of an underwater moving target measured in practice is attached to the end of the paper.