Detection of noise-induced ultrasonic sensor blindness

1. A controller for a piezoelectric transducer, the controller comprising:

a transmitter to drive a piezoelectric element during actuation intervals to generate acoustic bursts;

a receiver to sense a response of the piezoelectric element to echoes of each acoustic burst, the receiver including a front-end amplifier to amplify a signal from the piezoelectric element;

a processing circuit coupled to the transmitter and to the receiver, the processing circuit operable to apply echo-detection processing to said response; and

a blindness detector to detect saturation of the front-end amplifier outside of the actuation intervals, wherein the blindness detector includes: an envelope detector that measures a wideband envelope of the response outside of the actuation interval; and a comparator that compares the wideband envelope to a threshold representing saturation of the front-end amplifier.

2. The controller of claim 1 , wherein the blindness detector detects saturation immediately prior to each actuation interval.

3. The controller of claim 1 , further comprising: an analog-to-digital converter subsequent to the front-end amplifier, the analog-to-digital converter providing a digital response signal; a bandpass filter centered on a carrier frequency of the acoustic bursts to produce a filtered signal from the digital response signal; a second envelope detector that measures an envelope of the filtered signal during a noise measurement interval prior to each actuation interval; and a second comparator that compares the measured envelope of the filtered signal to a second threshold representing excessive environmental noise.

4. The controller of claim 3 , further comprising an I/O controller that communicates a sensor fault if the blindness detector detects saturation and if the second comparator detects excessive environmental noise during the noise measurement interval.

5. The controller of claim 1 , wherein the controller includes an analog-to-digital converter subsequent to the front-end amplifier, the analog-to-digital converter providing a digital response signal; and wherein the blindness detector operates on the digital response signal.

6. The controller of claim 1 , wherein the controller includes an analog-to-digital converter subsequent to the front-end amplifier, the analog-to-digital converter providing a digital response signal; and wherein the blindness detector operates on an analog output signal from the front-end amplifier.

7. A method of operating a piezoelectric-based sensor, the method comprising: driving a piezoelectric transducer to generate a burst of acoustic energy during an actuation interval; during a measurement interval following the actuation interval, obtaining a response of the piezoelectric transducer with a receiver that includes a front-end amplifier coupled to the piezoelectric transducer; processing the response to sense echoes of the burst; and determining whether the response indicates sensor blindness during the measurement interval due to saturation of the front-end amplifier, wherein said determining further includes: measuring a wideband envelope of the response; and comparing the wideband envelope to a threshold representing saturation of the front-end amplifier.

8. The method of claim 7 , wherein said determining includes employing a reverberation detector to signal an end of the actuation interval.

9. The method of claim 7 , wherein said processing includes: digitizing an output of the front-end filter with optional gain control to obtain a digital response signal; measuring a narrowband envelope of the digital response signal during a noise measurement interval prior to the actuation interval; comparing the narrowband envelope to a threshold representing excessive environmental noise.

10. The method of claim 8 , wherein said determining includes:

measuring a wideband envelope of the response; and

communicating the wideband envelope measurement to a system controller for detection of sensor blindness.

11. The method of claim 7 , wherein the wideband envelope is measured from the response at an output of the front-end amplifier.

12. The method of claim 9 , wherein the wideband envelope is measured from the digital response signal.

13. A sensor that comprises: a piezoelectric transducer; and a controller that drives the piezoelectric transducer to generate bursts of acoustic energy during actuation intervals and that obtains responses of the piezoelectric transducer during measurement intervals with a receiver that includes a front-end amplifier coupled to the piezoelectric transducer, the controller including a blindness detector that detects saturation of the front-end amplifier outside of the actuation intervals, wherein the blindness detector includes: an envelope detector that measures a wideband envelope of the response during each measurement interval.

14. The sensor of claim 13 , wherein the controller further includes a reverberation detector that determines a beginning of each measurement interval.

15. The sensor of claim 13 , wherein the controller further includes an I/O controller that communicates a sensor fault if the blindness detector detects saturation of the front-end amplifier.

16. The sensor of claim 13 , wherein the controller includes an analog-to-digital converter subsequent to the front-end amplifier, the analog-to-digital converter providing a digital response signal; and wherein the blindness detector operates on the digital response signal.

17. The sensor of claim 13 , wherein the controller includes an analog-to-digital converter subsequent to the front-end amplifier, the analog-to-digital converter providing a digital response signal; and wherein the blindness detector operates on an analog output signal from the front-end amplifier.