Echo detection with background noise based screening

A park assist control system, comprising a microcontroller, at least one a controller for an acoustic transducer, and a communication bus coupling the microcontroller and said at least one controller, the controller comprising:

• a transmitter to drive the acoustic transducer with a driving signal to generate acoustic bursts;
• a receiver to sense a response of the acoustic transducer to echoes of each acoustic burst;
• a processing circuit coupled to the receiver to convert said received response into output data;
• and
• an interface to convey said output data over the communication bus,
• wherein at least one of the processing circuit and the microcontroller is configured to:
• correlate said response with a pulse pattern to obtain a correlated response;
• distinguish peak areas from non-peak areas in said correlated response;
• derive a noise level in a portion of said correlated response using only the non-peak areas within said portion;
• calculate a signal to noise ratio (SNR) for a peak signal within the portion as a ratio of a peak value for the peak signal to said the noise level;
• and
• accept the peak signal as an echo only if the SNR for said peak signal exceeds a predetermined threshold.

A method of operating a piezoelectric-based sensor, the method comprising:

• driving a piezoelectric transducer to generate a burst of acoustic energy;
• obtaining a response from the piezoelectric transducer;
• correlating said response relative to said driving signal to obtain a correlated response;
• distinguish peak areas from non-peak areas in said correlated response;
• deriving a noise level in a portion of said correlated response using only the non-peak areas within said portion;
• calculating a signal to noise ratio (SNR) for a peak signal within the portion as a ratio of a peak value of for the peak signal to the noise level;
• and
• accepting the peak signal as an echo only if the SNR for said peak signal exceeds a predetermined threshold.

A controller for an acoustic transducer, the controller comprising:

• a transmitter drive the acoustic transducer with a driving signal to generate acoustic bursts;
• a receiver to sense a response of the acoustic transducer to echoes of each acoustic burst;
• a processing circuit coupled to the transmitter and to the receiver, the processing circuit configured to convert said received response into output data by:
• correlating said response to said driving signal to obtain a correlated response;
• distinguishing peak areas from non-peak areas in said correlated response;
• using the non-peak areas in a portion of the correlated response to derive a noise level;
• calculating a signal to noise ratio (SNR) for a peak signal within the portion as a ratio of a peak value for the peak signal to the noise level;
• and
• identifying the peak signal as a ground reflection if the SNR falls below a predetermined threshold.