Frequency hopping waveforms for continuous active sonar

Due to the relatively low speed of sound long range active sonar has a low update rate compared to radar systems. A possible solution to mitigate this problem is continuous active sonar. The source transmits sound continuously resulting in a continuous return echo. A problem is separating the transmission from the (weaker) returns from the target. This may be accomplished by transmitting very long linear frequency modulated (LFM) chirps so that the transmission and any target return are at different frequencies but this restricts the range resolution of the sonar system. In this paper, frequency hopping pulses are explored as an alternative approach to distinguish between the transmission and a target return.