System and method for eliminating audible noise for ultrasonic transducer

• US 6,243,323 B1
• Filed: 01/27/1999
• Issued: 06/05/2001
• Est. Priority Date: 01/27/1999
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Li, Songnian
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US09/237,850
• Time in Patent Office: 860 Days
• Field of Search: 367/99, 367/138, 367/96, 280/735
• US Class Current: 367/138
• CPC Class Codes: G01S 15/102 using transmission of pulses having some particular characteristics

Abstract

An ultrasonic ranging system and method for detecting the presence of and distance to a target using ultrasonic sound waves generated by an ultrasonic transducer with reduced audible noise. Electrical ultrasonic signal pulses are modulated according to a smooth modulation envelope and a transducer drive signal is generated from the modulated signal pulses. The transducer drive signal drives an ultrasonic transducer which generates ultrasonic sound waves for transmission in a desired path, and further receives ultrasonic sound waves reflected from targets in the transmission path. The received ultrasonic sound waves are converted to an electrical signal that is processed by a processor to provide time and distance information to the target. The distance information is computed by using a middle time value for the transmitted and received signals.

Claims

1. A method for producing ultrasonic sound waves with an ultrasonic transducer to realize reduced audible noise, said method comprising the steps of:

generating an electrical pulsed signal at an ultrasonic frequency;

generating a modulation envelope having a contour that gradually changes from a low amplitude to a high amplitude and then back to a low amplitude;

modulating said pulsed signal with said modulation envelope such that said pulsed signal bas an amplitude that varies according to the modulation envelope, wherein said step of modulating comprises amplitude modulating said pulsed signal based on a substantially sine wave contoured modulation envelope;

generating a transducer drive signal based on said modulated pulsed signal; and

applying the transducer drive signal as an input to an ultrasonic transducer to produce ultrasonic sound waves with reduced audible noise effects.

2. The method as defined in claim 1 further comprising the step of transmitting said ultrasonic sound waves from said ultrasonic transducer in a transmission path.

3. The method as defined in claim 2 further comprising the steps of:

receiving ultrasonic sound waves reflected from a target in said transmission path;

converting said received reflected ultrasonic sound waves to an electrical signal; and

processing said converted electrical signal to obtain time and distance information to said target.

4. The method as defined in claim 3, wherein said step of transmitting further comprises directing said ultrasonic sound waves in a transmission path in a vehicle for use in an ultrasonic ranging system.

5. The method as defined in claim 1 further comprising the step processing said modulated pulsed signal with transmit circuitry to generate said transducer drive signal.

6. A method for sensing the presence of a target and distance to the target with an ultrasonic transducer to realize reduced audible noise, said method comprising the steps of:

generating an electrical pulsed signal at an ultrasonic frequency;

generating a modulation envelope having a contour that gradually changes from a low amplitude to a high amplitude and then back to a low amplitude;

modulating said pulsed signal with said modulation envelope such that said pulsed signal has an amplitude that varies according to the modulation envelope, wherein said step of modulating includes the step of amplitude modulating said pulsed signal based on a substantially sine wave contoured modulation envelope;

generating a transducer drive signal based on said modulated pulsed signal;

applying the transducer drive signal as an input to an ultrasonic transducer to produce ultrasonic sound waves with reduced audible noise effects;

transmitting said ultrasonic sound waves in a transmission path;

receiving said ultrasonic sound waves reflected from a target in said transmission path;

converting said received reflected sound waves to an electrical signal; and

processing said converted electrical signal to obtain time and distance information to said target.

7. The method as defined in claim 6, wherein said step of transmitting further comprises transmitting said ultrasonic sound waves in a transmission path in a vehicle.

8. The method as defined in claim 7, wherein said step of transmitting further comprises transmitting said ultrasonic sound waves in said transmission path in a passenger compartment in said vehicle.

9. The method as defined in claim 6, wherein said step of modulating said pulsed signal comprises the step of amplitude modulating said pulsed signal.

10. An ultrasonic ranging system comprising:

a pulse signal generator for generating a series of electrical signal pulses at an ultrasonic frequency;

a modulator for modulating said signal pulses in a modulation envelope so that said signal pulses generally vary in magnitude from a low amplitude to a high amplitude and then back to a low amplitude, wherein said modulation envelope has a substantially sine wave contour;

circuitry for generating a transducer drive signal as a function of said modulated signal pulses;

an ultrasonic transducer for converting said transducer drive signal to ultrasonic sound waves and transmitting said ultrasonic sound waves in a transmission path, said ultrasonic transducer further receiving reflected ultrasonic sound waves reflected from a target in said transmission path and converting said received reflected sound waves to an electrical signal; and

a processor for processing said received reflected signal pulses and producing time and distance information to said target.

11. The ultrasonic ranging system as defined in claim 10, wherein said circuitry comprises a transceiver for transmitting said transducer drive signal to said transducer and for receiving said received reflected signal pulses.

12. The ultrasonic ranging system as defined in claim 11 further comprising an amplifier for amplifying said received reflected electrical signal.

13. The ultrasonic ranging system as defined in claim 10, wherein said modulator comprises an amplitude modulator.