The spectrogram correlation and transformation receiver, revisited

The spectrogram correlation and transformation (SCAT) receiver has been proposed as a model for the receiver structure used by fm bats. The main contribution of this paper lies in the analysis of which features of the proposed model are responsible for its high accuracy in estimating arrival times of overlapping echoes. Apart from providing an answer to this question, the analysis will also indicate the limitations of the SCAT receiver. In particular, it is shown that the temporal block of the SCAT receiver returns erroneous results for interecho delays < 20 microseconds and for interecho amplitude ratios > 6 dB. It is also shown that the spectral block of the SCAT receiver generates spurious arrival times if more than two overlapping echoes are present. Finally, it is discussed how the characteristic measurement errors predicted by this analysis can be used to further investigate the accuracy of the SCAT receiver as a model of the receiver structure used by fm bats.