Using spread spectrum coded pings in active sonar technology

Abstract

Performance of coded signals in active Sound Navigation and Ranging (SONAR) technology is studied in this work. In this work, the possibility of having covertness and environment friendliness in SONAR systems is investigated. Spread spectrum ping signal is considered to achieve low probability of detection and interception, while maintaining good performance. Direct Sequence Spread Spectrum (DSSS) coded transmitted signals having a sequence type of maximal with lengths from 7 chips to 127 chips and tone burst pulse having single length as a reference signal are used as spread spectrum ping signal. The length of the tone burst pulse can not be increased indefinitely because of the multipath propagation. The problem of detection and localization of the targets and the cross correlation properties of the maximal length sequences are investigated as well. The Signal to Noise Ratio (SNR) and Signal to Interference and Distortion ratio (SINAD) are important parameters in detection and localization of the targets. It is found that as the number of chip length increases, the SNR and SINAD increase but the improvement of the SINAD is comparatively less because of the cross correlation properties of the maximal length sequences.