Ultrasonic sensor with echo magnification
Sensors, sensor controllers, and sensor control methods may employ an echo-magnification technique to improve threshold-based echo detection. In one illustrative embodiment, a sensor controller includes: a transmitter, a receiver, and a processing circuit coupled to the transmitter and to the receiver. The transmitter drives a piezoelectric element to generate acoustic bursts. The receiver senses a response of the piezoelectric element to echoes of each acoustic burst. The processing circuit is operable to apply echo-detection processing to the response by: identifying an interval of the response representing at least a portion of a potential echo; deriving a modified response from the response by selectively magnifying the response during said interval; and using the modified response to detect an echo.
1. A controller for a piezoelectric transducer, the controller comprising:
a transmitter to drive a piezoelectric element to generate acoustic bursts;
a receiver to sense a response of the piezoelectric element to echoes of each acoustic burst; and
a processing circuit coupled to the transmitter and to the receiver, the processing circuit operable to apply echo-detection processing to said response, said processing including:
identifying an interval of the response representing at least a portion of a potential echo;
deriving a modified response from the response by selectively magnifying the response during said interval; and
using the modified response to detect an echo.
2. The controller of claim 1 , wherein said identifying an interval includes:
comparing the response to an adaptive threshold to produce a comparison signal; and
detecting an edge in the comparison signal.
3. The controller of claim 2 , wherein said processing further includes deriving the adaptive threshold from the response signal using a constant false alarm rate (CFAR) process.
4. The controller of claim 2 , wherein said identifying further includes comparing an estimated derivative to a threshold.
5. The controller of claim 1 , wherein the interval corresponds to a rising edge of an echo pulse.
6. The controller of claim 1 , wherein the interval corresponds to a falling edge of an echo pulse.
7. The controller of claim 1 , wherein said selectively magnifying includes multiplying by a scale factor greater than unity.
8. The controller of claim 1 , wherein said selectively magnifying includes applying a nonlinear function to the response during said interval.
9. The controller of claim 1 , wherein said selectively magnifying includes reducing the response outside of said interval.
10. The controller of claim 1 , wherein the echo is detected by comparing the modified response to a predetermined threshold template.
11. 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; and
processing the response to sense echoes of the burst, said processing including:
identifying a potential echo interval of the response representing at least a portion of a potential echo;
deriving a modified response from the response by selectively magnifying the response during said potential echo interval; and
using the modified response to detect an echo.
12. The method of claim 11 , wherein said identifying a potential echo interval includes:
comparing the response to an adaptive threshold to produce a comparison signal; and
detecting an edge in the comparison signal.
13. The method of claim 12 , wherein said processing further includes deriving the adaptive threshold from the response signal using a constant false alarm rate (CFAR) process.
14. The method of claim 12 , wherein said identifying further includes comparing an estimated derivative to a threshold.
15. The method of claim 11 , wherein the potential echo interval corresponds to a rising edge of an echo pulse.
16. The method of claim 11 , wherein the potential echo interval corresponds to a falling edge of an echo pulse.
17. The method of claim 11 , wherein said selectively magnifying includes multiplying by a scale factor greater than unity.
18. The method of claim 11 , wherein said selectively magnifying includes applying a nonlinear function to the response during said potential echo interval.
19. The method of claim 11 , wherein said selectively magnifying includes reducing the response outside of said potential echo interval.
20. The method of claim 11 , wherein the echo is detected by comparing the modified response to a predetermined threshold template.
21. A method of manufacturing a controller for a piezoelectric transducer, the method comprising:
providing a transmitter to drive a piezoelectric element to generate acoustic bursts;
creating a receiver to sense a response of the piezoelectric element to echoes of each acoustic burst; and
coupling a processing circuit to the transmitter and to the receiver, the processing circuit operable to apply echo-detection processing to said response, said processing including:
identifying an interval of the response representing at least a portion of a potential echo;
deriving a modified response from the response by selectively magnifying the response during said interval; and
using the modified response to detect an echo.
22. The method of claim 21 , wherein said identifying an interval includes:
comparing the response to an adaptive threshold to produce a comparison signal; and
detecting an edge in the comparison signal.
23. The method of claim 22 , wherein said processing further includes deriving the adaptive threshold from the response signal using a constant false alarm rate (CFAR) process.