Exploiting close-to-the-sensor multipath reflections using a human-hearing-inspired model

We propose a simple three-dimensional (3-D) direction-finding system that exploits multipath reflections close to the sensors to improve performance by increasing the effective array aperture. Such close-range multipath reflections can originate, for example, from parts of the platform on which the sensor is mounted. Our system is inspired by the human auditory system where multipath reflections from the external ear (pinna) enable 3-D direction finding. To demonstrate the advantage of exploiting multipath reflections, we consider a simple example of a passive system with only one sensor and two nearby reflectors. First, we present a parametric measurement model and then compute the asymptotic Cramér-Rao bound on the 3-D direction estimates for a stochastic source signal of unknown parametrized spectrum. We provide a few numerical examples to illustrate our analytical results. We find that for this example additional reflectors and a wider source spectrum can achieve better direction estimates.