Acoustic distance measuring circuit and method for low frequency modulated (LFM) chirp signals

A method comprising:

• generating a chirp signal at a frequency generator at a first time, wherein the frequency generator provides the chirp signal to determine a position of an obstacle;
• receiving, at a transmitter amplifier, the chirp signal for transmitting the chirp signal to an acoustic transducer;
• providing, by the acoustic transducer, a received input signal to a sensing circuit;
• filtering an in-phase portion and a quadrature portion of the received input signal, by a digital filter;
• calculating a phase of the received input signal in response to filtered in-phase and quadrature portions;
• determining a received input signal frequency slope in response to the phase;
• comparing the received input signal frequency slope to a chirp signal frequency slope and detecting an object in response to the received input signal frequency slope being approximately equal to the chirp signal frequency slope;
• and
• determining a distance of the object corresponding to a frequency shift of the received input signal frequency slope and an extrapolated chirp signal frequency slope extended from the generated chirp signal.

An acoustic distance measuring circuit, comprising:

• a frequency generator having an output for providing a chirp signal having a chirp signal frequency slope;
• a transmitter amplifier having an input coupled to the output of the frequency generator, and an output adapted to be coupled to an acoustic transducer;
• a sensing circuit having an input adapted to be coupled to the acoustic transducer, for determining a frequency slope of an input signal;
• and
• a controller coupled to the sensing circuit having an input for receiving the frequency slope of the input signal, wherein the controller is operable to compare the frequency slope of the input signal to the chirp signal frequency slope and to detect an object in response to the frequency slope of the input signal being approximately equal to the chirp signal frequency slope, wherein the controller is also operable to determine a distance of the object corresponding to a frequency shift of the frequency slope of the input signal and an extrapolated chirp signal frequency slope extended from the chirp signal.