Reducing or eliminating transducer reverberation

Abstract

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.

What is claimed is: 
     
         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.