Piezoelectric transducer with model-based field equalization
Disclosed sensors, sensor controllers, and sensor control methods enhance transducer performance using a model-based equalization method that can be performed in the field. One illustrative method for operating a piezoelectric-based sensor includes: sensing a response of a piezoelectric transducer as a function of frequency; deriving parameter values of an equivalent circuit for the piezoelectric transducer from the response; using a squared magnitude of the equivalent circuit's transfer function to determine a system level selectivity; and adapting at least one operating parameter of the sensor based on the system level selectivity. One illustrative controller for a piezoelectric transducer includes: a transmitter that drives the piezoelectric transducer; a receiver that senses a response of the piezoelectric transducer; and a processing circuit coupled to the transmitter and to the receiver to calibrate the transducer using the foregoing method.
1. A method of operating a piezoelectric-based sensor, the method comprising:
sensing a response of a piezoelectric transducer as a function of frequency;
deriving parameter values of an equivalent circuit for the piezoelectric transducer from the response;
combining a stored compensation curve with a squared magnitude of a transfer function of the equivalent circuit to determine a system level selectivity, the stored compensation curve representing a difference between a previously measured system level selectivity curve and a squared transfer function magnitude curve; and
adapting at least one operating parameter of the sensor based on the system level selectivity.
2. The method of claim 1 , wherein said adapting comprises adjusting a transmit signal current to counteract a variation in transmitted sound pressure level represented by a change of the system level selectivity.
3. The method of claim 1 , wherein said adapting comprises adjusting a receive signal gain to counteract a variation in receiver sensitivity represented by a change of the system level selectivity.
4. The method of claim 1 , wherein said adapting comprises adjusting a correlator attenuation to counteract a channel imbalance indicated by the system level selectivity.
5. The method of claim 1 , wherein said using includes: normalizing the squared magnitude of the transfer function of the equivalent circuit.
6. The method of claim 1 wherein said combining includes includes:
measuring a temperature; and
based on the temperature, selecting the stored compensation curve from multiple stored compensation curves.
7. The method of claim 1 , further comprising: performing target detection after adapting the at least one operating parameter.
8. A controller for a piezoelectric transducer, the controller comprising:
a transmitter that drives the piezoelectric transducer;
a receiver that senses a response of the piezoelectric transducer; and
a processing circuit coupled to the transmitter and to the receiver to perform calibration, the calibration including:
sensing a phase response of a piezoelectric transducer as a function of frequency;
deriving parameter values of an equivalent circuit for the piezoelectric transducer from the phase response;
combining a stored compensation curve with a squared magnitude of a transfer function of the equivalent circuit to determine a system level selectivity, the stored compensation curve representing a difference between a previously measured system level selectivity curve and a squared transfer function magnitude curve; and
adapting at least one operating parameter of the sensor based on the system level selectivity.
9. The controller of claim 8 , wherein said adapting comprises adjusting a transmit signal current to counteract a variation in transmitted sound pressure level represented by a change of the system level selectivity.
10. The controller of claim 8 , wherein said adapting comprises adjusting a receive signal gain to counteract a variation in receiver sensitivity represented by a change of the system level selectivity.
11. The controller of claim 8 , wherein said adapting comprises adjusting a correlator attenuation to counteract a channel imbalance indicated by the system level selectivity.
12. The controller of claim 8 , wherein said using includes: normalizing the squared magnitude of the transfer function of the equivalent circuit.
13. The controller of claim 8 , wherein said combining includes:
measuring a temperature; and
based on the temperature, selecting the stored compensation curve from multiple stored compensation curves.
14. The controller of claim 8 , further comprising: performing target detection after adapting the at least one operating parameter.
15. A system that comprises:
a transmitter that drives the piezoelectric transducer;
a receiver that senses a response of the piezoelectric transducer; and
one or more controllers collectively configured to calibrate at least one of the transmitter and to the receiver, the calibration including:
sensing a phase response of a piezoelectric transducer as a function of frequency;
deriving parameter values of an equivalent circuit for the piezoelectric transducer from the phase response;
combining a stored compensation curve with a squared magnitude of a transfer function of the equivalent circuit to determine a system level selectivity, the stored compensation curve representing a difference between a previously measured system level selectivity curve and a squared transfer function magnitude curve; and
adapting at least one operating parameter of the sensor based on the system level selectivity.
16. The system of claim 15 , wherein said combining includes:
measuring a temperature; and
based on the temperature, selecting the stored compensation curve from multiple stored compensation curves.
17. The system of claim 15 , further comprising: performing target detection after adapting the at least one operating parameter.