PREDICTION OF INCOHERENT DOPPLER SONAR PERFORMANCE FOR REPEAT-SEQUENCE CODED PULSES FOR SCATTER FIELDS WITH SHARP CHANGES IN ECHO STRENGTH, FLOW TURBULENCE AND NOISE

摘要

Repeat-sequence coding is a simple method for improving the precision of velocity estimates from incoherent Doppler sonars. However, the performance of the coding can be severely degraded by noise and decorrelation of the signal. For an incoherent sonar system the most important sources for decorrelation are flow turbulence, nonuniform echo strengths within the sample volume, and beam divergence. Closed form formulas for the performance of repeat-sequence coding have been derived for scatter fields with exponential varying echo strength, flow turbulence and white noise. The accuracy of these expressions has been assessed by comparison with results from computer simulation. The formula for the influence of exponentially varying intensity has further been compared with field measurements. The velocity errors predicted by the derived formulas have been found to be in reasonable agreement with both simulations and measurements.