CORRELATION RECEIVERS USING LAGUERRE FILTER BANKS FOR MODELING NARROW-BAND ULTRASONIC ECHOES AND ESTIMATING THEIR TIME-OF-FLIGHTS

A class of baseband correlation receivers is developed for estimating the time-of-flight of a narrowband signal. In contrast to conventional correlation receivers that contain a perfectly known replica of the s ignal, the signal shape is unknown to the proposed receiver. A paramet ric model of the signal envelope is therefore built, concurrently with the process of time-of-flight estimation. The identification of the m odel parameters can be pursued by assuming that a few signal constrain ts are satisfied at the time instant of signal onset: the constraints concern the value of the signal envelope and of its first time derivat ive. The correlation receivers perform a series expansion of the signa l envelope by a set of Laguerre basis functions; the outputs of the La guerre filter bank that computes the running Laguerre transform are us ed to build a parametric model of the unknown envelope and to estimate its time-of-flight. Simple variations of the correlation receivers ar e proposed, which differ from each other in the use they make of the s ignal constraints. The correlation receivers are applied to process na rrowband echoes from in-air ultrasonic sensors. Potential applications are object identification and surface profiling in the robotic field. Computer simulations and experiments using a simple pulse-echo sensor system are presented.