REDUCING OR ELIMINATING TRANSDUCER REVERBERATION

1 . An obstacle monitoring system comprising:

a transducer that receives an ultrasonic echo from an obstacle and generates a signal based on the echo;

a controller coupled to the transducer that is calibrated based on a response of the transducer and a coupling circuit; and

circuitry generating a damping current, controlled by the controller, that reduces or eliminates reverberation of the transducer.

2 . The system of claim 1 , wherein the controller is selected from the group consisting of: damping digital filter, analog filter, correlator, integrator, and derivator.

3 . The system of claim 1 , wherein the controller is recalibrated upon ambient temperature changes.

4 . The system of claim 1 , wherein the controller is recalibrated upon changes in the transducer or transducer characteristics.

5 . The system of claim 1 , wherein the obstacle is monitored up to at least five centimeters from the transducer.

6 . The system of claim 1 , wherein the transducer comprises a two-pin piezo when used with a transformer or without a transformer.

7 . The system of claim 1 , further comprising an automobile on which the transducer is located.

8 . The system of claim 1 , wherein the transducer is located on a bumper of the automobile.

9 . An obstacle monitoring method comprising:

receiving an ultrasonic echo from an obstacle;

generating a signal based on the echo;

calibrating a circuit by selecting coefficients for a filter based on a response to the signal; and

reducing or eliminating reverberation by introducing a damping current controlled by a controller.

10 . The method of claim 9 , wherein the controller is selected from the group consisting of: damping digital filter, analog filter, correlator, integrator, and derivator.

11 . The method of claim 9 , wherein the filter is a digital damping finite impulse response (“FIR”) filter.

12 . The method of claim 9 , further comprising predicting a time when the magnitude of reverberation falls under a threshold and interpreting a signal, received after the predicted time with a magnitude above the threshold, as another echo and not as a continuation of reverberation.

13 . The method of claim 9 , wherein calibrating the circuit further comprises measuring a resonance frequency and modifying the coefficients for the filter based on the resonance frequency.

14 . The method of claim 9 , wherein calibrating the circuit further comprises measuring a junction or sensor temperature and modifying the coefficients for the filter based on the junction or sensor temperature.

15 . The method of claim 9 , wherein calibrating the circuit further comprises measuring transmission power of a transmission (piezo voltage) that causes the echo and modifying the coefficients for the filter based on the transmission power (piezo voltage).

16 . The method of claim 9 , further comprising determining a distance from a transducer receiving the echo to the obstacle.

17 . The method of claim 16 , further comprising generating an alert if the distance is below a threshold.

18 . The method of claim 16 , further comprising performing a corrective action if the distance is below a threshold.

19 . The method of claim 18 , wherein the corrective action is applying a braking force to an automobile on which the transducer is located.

20 . An obstacle monitoring system comprising:

a transducer that receives an ultrasonic echo from an obstacle and generates a signal based on the echo; and

a controller that drives the transducer in a first mode or a second mode;

wherein the first mode comprises driving the transducer at a resonance frequency for relatively longer distances between the transducer and the obstacle; and

wherein the second mode comprises driving the transducer at an out-of-resonance frequency, lower or higher than the resonance frequency, for relatively shorter distances between the transducer and the obstacle to reduce or eliminate reverberation of the transducer.