Bat-inspired distance measurement using phase information.

Abstract

This paper shows the use of phase measurement to estimate the distance to a target. Inspiration for this work comes from the observation that bats have been shown to have exceptional resolution with regard to target detection when searching during flight. Au and Simmons [“Echolocation in dolphins and bats,” Phys. Today 45(7), 40–45 (2007)] concluded bats with a center frequency of about 80 kHz (i.e., 4-mm wavelength), and 40-kHz bandwidth can have a resolution of distance in air approaching 20 μm. For this frequency, we see that the resolution achieved by the bat is about 200 times better than λ/2 (i.e., 2 mm at this frequency), which is usually used as a guide for resolution for analog systems. Moreover, Au and Simmons show, using time-frequency analysis, that there are essentially two frequencies present at any particular time within a single bat pulse. Considering this use of two frequencies we may infer a distance. A new bat-inspired algorithm is presented. This is based on phase measurement and, when applied to underwater acoustics, shows that a resolution of 1/50 of the wavelength can be achieved in practice.