Method for determining echo distance using autocorrelation in time of flight ranging systems

A pulse-echo acoustic ranging system comprising:

• (a) a transducer for emitting acoustic pulses and detecting reflected echoes;
• (b) a controller having a receiver component and a transmitter component;
• (c) said transducer having an input port operatively coupled to said transmitter component and being responsive to said transmitter component for emitting said acoustic pulses, and said transducer including an output port operatively coupled to said receiver component for outputting reflected echoes coupled by said transducer,
• (d) said receiver component converting said reflected acoustic pulses into a receive signal, said receive signal having a plurality of peaks and troughs;
• (e) said controller including a first program component for creating a plurality of correlation signals by adding said filtered signal to a copy of said filtered signal shifted by a plurality of time units, a second program component for identifying a correlation indicator of each of said correlation signals, and a third program component for selecting an echo time based upon a maximum correlation as determined by one of said correlation indicators, said echo time being the time shift at which said maximum correlation occurs, and whereby the selected time indicates the echo distance travel time.