A semi-analytical geometrical acoustics method for numerical simulation of ultrasound based motion sensing
We present a semi-analytical geometrical acoustics method to numerically simulate ultrasonic signal characteristics pertinent to motion sensing applications in indoor environments. The proposed methodology treats motion sensing from the first-principles in the sense that the expressions for acoustic field from the source, that scattered by the target and then received at the receiver are all derived from a kinematic standpoint incorporating target motion into consideration. A series of examples are presented throughout to demonstrate the effect of source directivity, wall reflections, and motion trajectories on the Doppler signal strength and frequency characteristics observed for motion sensing applications. Finally, we present a comparison of simulated results with experimental results on data acquired with a human target moving in an environment with an ultrasonic source and receiver. We specifically compare the baseband signal characteristics and their corresponding Short-time Fourier Transforms that depict Doppler frequency characteristics and show them to be in good qualitative agreement.