SELF-TUNING ACOUSTIC MEASUREMENT SYSTEM

• US 20110261652A1
• Filed: 04/26/2010
• Published: 10/27/2011
• Est. Priority Date: 04/26/2010
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Horsky, Pavel, Suchy, Tomas, Koudar, Ivan
• Granted Patent: US 8,699,299 B2
• Time in Patent Office: Days
• US Class Current: 367/97
• CPC Class Codes: B06B 1/0253 taken directly from the generator circuit
• CPC Class Codes: G01S 15/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurement G01S15/32
• CPC Class Codes: G01S 15/931 of land vehicles
• CPC Class Codes: G01S 7/52036 using analysis of echo signal for target characterisation
• CPC Class Codes: G01S 7/524 Transmitters

Abstract

In one embodiment, an acoustic distance measurement system can dynamically adjust its measurement frequency to a frequency that is within a preselected bandwidth of the resonant frequency of an acoustic transducer used in making acoustic distance measurements.

Claims

1. A method of forming a distance measurement circuit, comprising:

configuring the distance measurement circuit to form a driving signal to drive an ultrasonic transducer;

configuring the distance measurement circuit to substantially cease the driving signal;

configuring the distance measurement circuit to receive a resonant signal in response to ceasing the driving signal;

configuring the distance measurement circuit to determine a present resonant frequency of the resonant signal;

configuring the distance measurement circuit to tune a measurement frequency of the distance measurement circuit to a frequency within a predefined bandwidth of the present resonant frequency; and

configuring the distance measurement circuit to form a measurement signal at the measurement frequency.

2. The method of claim 1, wherein the driving signal is at a frequency that is presently based on a previously-determined resonant frequency of the ultrasonic transducer.

3. The method of claim 1, further comprising configuring the distance measurement circuit to repeatedly provide the driving signal, cease the driving signal, receive the resonant signal, and form the measurement signal at preselected time intervals.

4. The method of claim 1, further comprising configuring the distance measurement circuit to provide the driving signal, cease the driving signal, receive the resonant signal, and determine the present resonant frequency responsively to commencement of, and as an initialization for conducting a distance measurement operation.

5. The method of claim 1, wherein configuring the distance measurement circuit to determine the present resonant frequency comprises configuring the distance measurement circuit to determine the present resonant frequency following a delay period after substantially ceasing the driving signal.

6. The method of claim 1, wherein configuring the distance measurement circuit to determine the present resonant frequency comprises configuring the distance measurement circuit to detect a number of resonant oscillations in a preselected time interval.

7. The method of claim 1 wherein, configuring the distance measurement circuit to determine the present resonant frequency comprises configuring the distance measurement circuit to determine the present resonant frequency while an amplitude of an envelope of the resonant frequency signal remains above a preselected threshold amplitude.

8. The method of claim 1, wherein the driving signal has a driving frequency, configuring the distance measurement circuit to determine the present resonant frequency comprises:

configuring the distance measurement circuit to apply the resonant signal to a demodulator operating at the driving frequency; and

configuring the distance measurement circuit to determine an offset of the present resonant frequency from the driving frequency based on an output of the demodulator as a result of applying the resonant signal to the demodulator while the demodulator is operating at the driving frequency.

9. The method of claim 8 wherein the demodulator is a zero intermediate frequency (ZIF) demodulator, the method further comprises:

configuring the ZIF demodulator to produce a phase signal output having a slope proportional to a difference between the driving frequency and the present resonant frequency;

configuring the distance measurement circuit to determine the slope of the phase signal over a time period; and

configuring the distance measurement circuit to determine the present resonant frequency based on the slope of the phase signal and the driving frequency.

10. A self-tuning acoustic distance measurement circuit, comprising:

a driving circuit which generates a driving signal and is configured to selectively provide the driving signal to an acoustic transducer;

a frequency determination circuit which determines a resonant frequency from a resonant signal produced by the acoustic transducer responsively to the driving circuit stopping the driving signal, and further indicates the resonant frequency to the driving circuit; and

wherein the driving circuit sets a measurement frequency used to conduct acoustic measurement operations to a frequency within a preselected bandwidth of the resonant frequency.

11. The self-tuning acoustic distance measurement circuit of claim 10, wherein the self-tuning acoustic distance measurement circuit dynamically adjusts the measurement frequency to substantially maintain the measurement frequency at a preselected frequency offset from the resonant frequency during operation of the self-tuning acoustic distance measurement system.

12. The self-tuning acoustic distance measurement circuit of claim 10, wherein the driving signal is a tone signal at a driving frequency, the frequency determination circuit comprises a demodulator that mixes the resonant signal with the driving signal and produces a result indicative of a frequency difference between the resonant frequency and the driving frequency.

13. The self-tuning acoustic distance measurement circuit of claim 12, wherein the demodulator is a zero intermediate frequency demodulator.

14. The self-tuning acoustic distance measurement circuit of claim 10, wherein the frequency determination circuit determines the resonant frequency by counting a number of oscillations of the resonant signal that occur within a time period.

15. The self-tuning acoustic distance measurement circuit of claim 10, wherein the frequency determination circuit is further operable to wait a preselected period of time after the driving circuit stops the driving signal before determining the resonant frequency.

16. The self-tuning acoustic distance measurement circuit of claim 10, wherein the driving circuit is coupled to the acoustic transducer through a transformer.

17. A distance measurement circuit for conducting ultrasonic distance measurements, comprising:

an ultrasonic transmitter, including;

a tunable oscillator which generates an oscillator signal at a selected driving frequency; and

a signal generator coupled to the tunable oscillator and which generates a driving signal from the oscillator signal by pulsing the oscillator signal between selected start and stop times, wherein the driving signal is operable to cause an ultrasonic transducer to produce a resonant signal at a resonant frequency;

an ultrasonic receiver, including;

a signal processor operable to receive the resonant signal from the ultrasonic transducer and produce a frequency information signal; and

a frequency processor coupled to the signal processor that determines the resonant frequency from the frequency information signal and indicates the resonant frequency to the ultrasonic transmitter;

wherein the ultrasonic transmitter adjusts the tunable oscillator to maintain the selected driving frequency within a preselected bandwidth of the resonant frequency.

18. The apparatus of claim 17, wherein the signal processor is configured to count oscillations of the resonant signal, and the frequency processor determines the resonant frequency based on the count.

19. The apparatus of claim 17, wherein the signal processor comprises a demodulator operating at the driving frequency that mixes the driving frequency with the resonant frequency to determine a difference between the driving frequency and the resonant frequency as the frequency information signal.

20. The apparatus of claim 17, wherein the resonant signal has an envelope, the signal processor is operable to produce the frequency information signal while the envelope is above a preselected level, and after a delay period after the ultrasonic transmitter stops the driving signal.