James E. Barger
BBN Systems and Technologies, 70 Fawcett St., Cambridge, MA 02138
The detectability of signals (echoes) depends only upon the energy and bandwidth of the signals, in a wide variety of different interference backgrounds. This fact is represented in a sonar equation that is both written in terms of these quantities, and that also differs from the more traditional form that incorporated signal power and time span. Beyond this, fluctuations in the transient signal's arrival times, time spreads, arrival angles, and angle spreads; all affect target localization processing. Since a transient signal has a shorter time span than does a longer waveform with equal energy, the effects of propagation-induced fluctuations between successive transient signals can be different than between successive long-waveform signals. The potential for these differences is discussed for four different causes of fluctuation; multipath, refraction, direct-path fluctuation, and reflected path fluctuation.