The use of chirp overlapping properties for improved target resolution in an ultrasonic ranging system

The ability of many bat species to navigate, identify and capture prey has interested scientists for many years. It is known that bats possess extremely sophisticated echo location capabilities utilising chirp sequencing allied with an adaptive antenna system that enables extremely high resolution in 3-D space. One particularly interesting aspect is that bats appear to resolve and locate targets with scattering dimensions less than the wavelength of the emitted signals. They can identify the target shape by resolving multiple and closely reflecting points along the range axis. Properly harnessed, such techniques could possess significant potential for ultrasonic imaging. The feasibility of applying one aspect of bat behaviour, namely the use of overlapping frequency modulated signals to achieve improved ultrasonic image resolution, is investigated in this work. A one dimensional model is used to simulate the behaviour of a simple, layered ultrasonic system. The fundamental theory is based on the use of temporal and frequency information and improved resolution is demonstrated by resolving the resultant interference patterns in the frequency domain.