CutFM sonar signal design

Sonar-based underwater surveillance, including the problem of diver detection, is a challenging task. Particularly in reverberation limited environments like harbors and coastal waters, it is usually essential to utilize the Doppler effect caused by the target movement, in order to separate the diver from the quasi-stationary background. The common choice for Doppler processing systems is to use the continuous wave (CW) signal or one of its modifications. However, it is known that the CW waveform provides poor range resolution. In this paper a frequency modulation (FM) based Doppler selective signal, called cutFM, is introduced. The cutFM signal is characterized by a comparable Doppler resolution as that of the CW signal, but with improved range resolution. The paper provides Doppler processing gain estimates and the theoretical predictions concerning cutFM are supported by measurement results.