A low-cost digital delay line for bat biosonar research

Abstract

Bat biosonar research and bat neuroscience as a whole relies heavily on experiments to determine bat responses to various stimuli. Typically, these are presented to the bat using real world targets such prey insects, but also via artificial stimuli using an ultrasonic loudspeaker. One key component of artificial target creation is the use of delay lines. Analog delay lines have been used for decades to generate artificial targets at programmable ranges. More recently, digital delay lines have become the norm. This talk will present the details of the development of a very low-cost digital delay line that can produce bat echoes with up to three glints. The main delay between the bat and the target as well as the inter-glint spacing are programmable with delays as small as 5 μ s possible. The platform used is a commonly available SAMD51 microcontroller with a total system cost under $50. The talk will present experimental results, code development using commonly available programming tools, and schematics for an add-on board that uses microphone or general differential inputs. Finally, the talk will introduce an approach implement wideband Doppler shift (time-scaling) of digitally delayed echoes using direct memory access tools native to the SAMD51 microcontroller.