Reducing or eliminating transducer reverberation
An obstacle monitoring system includes a transducer that receives an ultrasonic echo from an obstacle and generates a signal based on the echo. The system further includes a controller coupled to the transducer that is calibrated based on a frequency response of the transducer and a coupling circuit. The system further includes circuitry generating a damping current, controlled by the controller, that reduces or eliminates reverberation of the transducer.
1 . An obstacle monitoring system comprising:
a transducer configured to transmit an ultrasonic pulse, configured to receive ar ultrasonic echo from an obstacle, and configured to generate a signal based on the echo the ultrasonic pulse causing post-transmission reverberation of the transducer;
an analog-to-digital converter (ADC) configured to digitize the signal from the transducer;
a digital damping filter calibrated based on a response of the transducer, the digital damping filter configured to convert the digitized signal from the transducer into a digital damping signal; and
a digital-to-analog converter (DAC) configured to convert the digital damping signal into a damping current that reduces or eliminates the post-transmission reverberation of the transducer.
2 . The system of claim 1 , further comprising: a controller configured to calibrate the digital damping filter based on a response of the transducer.
3 . The system of claim 2 , wherein the DAC is configured to supply a calibration pulse to the transducer and the response measured by the controller is the transducer's response to the calibration pulse.
4 . The system of claim 2 , wherein the controller is configured to calibrate the digital damping filter based on a frequency response of the transducer.
5 . The system of claim 2 , wherein the controller is configured to calibrate the digital damping filter based on a resonance frequency of the transducer.
6 . The system of claim 2 , wherein the controller is configured to use the digitized signal from the transducer to measure transmission power and is configured to calibrate the digital damping filter based on the transmission power.
7 . The system of claim 2 , wherein the digital damping filter comprises a finite impulse response (FIR) filter having coefficients set by the controller.
8 . The system of claim 7 , wherein the controller is configured to measure a junction or sensor temperature and configured to modify said coefficients based on the measured temperature.
9 . The system of claim 2 , wherein the controller is configured to determine a distance from the transducer to the obstacle based on the echo.
10 . An obstacle monitoring method comprising:
using an ultrasonic transducer to transmit an ultrasonic pulse and to obtain a receive signal, the receive signal including an ultrasonic echo from an obstacle, wherein the ultrasonic pulse causes post-transmission reverberation of the transducer;
calibrating a digital damping filter by selecting filter coefficients based on a response of the ultrasonic transducer;
using the digital damping filter to convert a portion of the receive signal into a digital damping signal; and
converting the digital damping signal into a damping current that reduces or eliminates the post-transmission reverberation of the transducer.
11 . The method of claim 10 , wherein the calibrating includes supplying a calibration pulse to the transducer to measure said response.
12 . The method of claim 10 , wherein the response is a frequency response of the transducer.
13 . The method of claim 10 , wherein the calibrating includes measuring a resonance frequency and selecting the filter coefficients based on the resonance frequency.
14 . The method of claim 10 , wherein the calibrating includes measuring transmission power and selecting the filter coefficients based on the transmission power.
15 . The method of claim 10 , wherein the digital damping filter is a finite impulse response (FIR) filter.
16 . The method of claim 10 , wherein the calibrating includes measuring a junction or sensor temperature and selecting said coefficients based on the measured temperature.
17 . The method of claim 10 , further comprising determining a distance from the transducer to the obstacle.
18 . The method of claim 17 , further comprising generating an alert if the distance is below a threshold.
19 . The method of claim 17 , further comprising performing a corrective action if the distance is below a threshold.
20 . The method of claim 19 , wherein the corrective action is applying a braking force to an automobile on which the transducer is located.
21 . A circuit comprising:
an analog-to-digital converter (ADC) configured to couple to a transducer configured to receive ultrasonic echoes from an obstacle in response to ultrasonic pulses that cause post-transmission reverberation of the transducer, the ADC configured to convert a signal from the transducer into a digitized signal;
a digital damping filter configured to convert the digitized signal into a digital damping signal;
a controller configured to calibrate the digital damping filter based on a pulse response of the transducer;
a digital-to-analog converter (DAC) configured to convert the digital damping signal into a damping current that reduces or eliminates the post-transmission reverberation of the transducer.