Detection of target in underwater acoustics raises various difficulties due to unpredictable noise interference which originates from clutter, reverberation, and variations of medium characteristics with time and location.
Hence, SNR and range resolutions of the conventional SONAR systems using a matched filter are generally poor, since the latter is optimum only in additive white noise. Furthermore, it cannot compensate for variations of detection threshold which are responsible for the resultant detection errors.
In this paper, the unpredictable interferences are compensated for by using an adaptive filter. It recursively estimates the channel impulse response based on the received echo signal. In low noise circumstances, the estimated impulse response is nearly the same as a true one, providing a good range resolution, and matched filters are used for the purpose of detection. It is shown through simulation that good performance can be achieved. Also, detection threshold remains unchanged without any additional equipment. Finally, we present several characteristics of the adaptive filter parameters.
