Time-Frequency Processing of Bat Sonar Signals
It is known that time-frequency distributions can be used for the demodulation of bat sonar signals and, in some cases, for detection-estimation tasks via a 2-D correlation process. In this paper, we formalize the intuitive notion of correlation of time-frequency structures in the simplified case of AM + FM signals. This results in a general time-frequency receiver structure depending only on a time-frequency smoothing function. According to the choice of this smoothing, it is shown that the receiver can vary continuously from a semi-coherent (matched filter and envelope detector) to a non-coherent (energetic) one. This suggests that both can be viewed as limiting cases of a unique time-frequency processing. The proposed approach is illustrated on the detection of echoes (over water) of signals emitted by Myotis daubentoni and recorded in the field.
KeywordsMatched Filter Wigner Distribution Echolocation Call Envelope Detector Eptesicus Fuscus
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