Image Number 3 for United States Patent #6128249.
An improved method is provided for operating a continuous wave sonar syst At time of transmission, a plurality of acoustic pulses are transmitted one right after another. Each pulse has a unique frequency and is of a time duration that is approximately one second long. The pulses are characterized by a separation frequency representing a difference in frequency between numerically successive frequencies. However, the pulses are staggered with respect to frequency. In the preferred embodiment, each successively transmitted one of the pulses is separated in frequency from an immediately preceding transmitted one of the pulses by an amount greater than the separation frequency. These multiple pulses seperated in time and in frequency, reduce the effects of frequency speading caused by the medium, resulting in a sonar with enhanced detection performance.