Echo‐echo correlation (EEC)

Traditional coherent processing of large BT product waveforms in active acoustic detection suffers apparent loss in echo energy due to channel multipath and/or target highlights. High resolution sonar used with targets at long ranges requires massive array processing and fast correlation, with heavy display loads. Echo‐Echo Correlation (EEC) is a new technique which finds the auto‐correlation of the echo, independent of pulse characteristics, multipath, or target velocity. For a given probability of detection, required decision thresholds are much lower with EEC than with standard procedures. The ECC output is not distorted by unknown Doppler, yet target velocity is readily computed. The computations are easily carried out in the time‐domain, and the display load is greatly reduced. Two experiments using EEC have been completed. The first was a deep ocean, bottom bounce operation using a submarine as a target and a surface ship as the sonar source. The EEC results were equal to or superior than those from the standard coherent technique. The second compared the losses caused by target multipath for EEC and the standard technique. The latter suffered much higher losses as a function of target aspect, bandwidth, and pulse type. EEC showed negligible losses.