Correlation Loss in Echo Ranging

In a correlation echo‐ranging system, many features of any correlation loss may be predicted without considering detailed mechanisms. Correlation loss may be due to both a spreading time delay, τ and a spreading in Doppler‐frequency shift φ. First, these effects are considered separately, for one‐way transmission and for two‐way transmission or echo ranging. Generally, the total correlation loss may be regarded as due to a two‐dimensional spreading in the τ‐φ plane. When τ and φ spreading are both significant, the loss for an FM pulse is much less than that for a noise pulse. The excess of the two‐way loss over the one‐way loss may often be about $112$ dB for an FM pulse and 3 dB for a noise pulse.