Communications – electrical: acoustic wave systems and devices – Transmitter systems – With beam forming – shaping – steering – or scanning
Reexamination Certificate
1999-01-27
2001-06-05
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Transmitter systems
With beam forming, shaping, steering, or scanning
Reexamination Certificate
active
06243323
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to ultrasonic ranging and, more particularly, to an ultrasonic ranging system and method for enhancing the utilization of an ultrasonic transducer, especially for use in the passenger compartment of a vehicle.
Ultrasonic sensing techniques have become widely acceptable for use in ranging systems for determining the presence of and distance to a target object. In a conventional ultrasonic ranging system, an ultrasonic transducer is employed which converts electrical signal pulses into mechanical motion. In turn, the mechanical motion creates ultrasonic sound waves that are transmitted through the atmosphere in a desired direction. Provided there is a target in its path, the sound waves reflect off the target and the reflected sound waves travel back to the ultrasonic transducer. The reflected sound waves, also referred to as the echo waves, mechanically deflect the ultrasonic transducer and, in response, a low voltage pulsed signal is generated. Since the speed of travel of the sound waves remains relatively fixed, the distance to the target is determined by measuring the time period between the transmitted and received signal pulses, and computing the distance as a function of the time period and the sound wave speed.
The transmitted and received ultrasonic sound waves are similar to audible sound waves, except the ultrasonic frequencies are generally much higher and therefore exceed the audible frequency range for human beings. Accordingly, human beings are generally unable to hear the radiated ultrasonic sound waves generated by the ultrasonic transducer. In many conventional applications, the ultrasonic ranging system is generally considered to be a quiet operating device. However, in practice it is recognized that an ultrasonic transducer creates undesired audible waves as a side effect when transmitting ultrasonic sound waves, particularly at certain strength levels. The presence of audible sound is even more noticeable where a high strength signal is required. It has been discovered that these undesirable audible sound waves generally provide a noticeable audible “tick” sounding noise which, in the past, has generally been considered acceptable for some applications. However, the audible “tick” noise generated by an ultrasonic transducer can be annoying when used in certain environments, such as inside the passenger compartment of a vehicle.
Accordingly, it is one object of the present invention to provide for a method of effectively reducing or eliminating the audible sound noise that may otherwise be produced by an ultrasonic transducer. It is another object of the present invention to provide for an ultrasonic transducer ranging system with reduced or eliminated audible sound noise. Yet, it is a further object of the present invention to provide for quiet and effective use of an ultrasonic transducer in a passenger compartment of a vehicle.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, an ultrasonic ranging system and method are provided for producing ultrasonic sound waves with an ultrasonic transducer while experiencing little or no audible sound, e.g., “tick” noise. The ultrasonic ranging system has a modulator that modulates a pulsed electrical signal according to a smooth modulation envelope, and a transceiver that generates an electrical drive signal based on the modulated signal. The ultrasonic ranging system includes an ultrasonic transducer for converting the electrical drive signal to ultrasonic sound waves for transmission in a transmit path. The ultrasonic transducer also receives reflected ultrasonic sound waves that are reflected from targets in the transmit path, and converts the reflected sound waves to an electrical signal. The converted received signal is processed, and the ultrasonic ranging system determines time and distance information to the target.
According to the method of producing ultrasonic sound waves according to the present invention, a pulsed electrical signal and a modulation envelope are generated, and the pulsed electrical signal is smoothly modulated in the modulation envelope. An electrical drive signal is generated with transmit circuitry based on the modulated signal. The transducer drive signal is applied to an ultrasonic transducer which converts the transducer drive signal to ultrasonic sound waves and transmits the sound waves in a transmit path. The smoothly modulated transducer drive signal causes the ultrasonic transducer to effectively produce ultrasonic sound waves while reducing or eliminating audible sound noise. The method can further receive those ultrasonic sound waves reflected from a target in the transmit path of the sound waves, convert the received reflected sound waves to an electrical signal, and determine time and distance information to the target.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
This application is one of two applications filed on the same date, both commonly assigned and having similar specifications and drawings, the other application being identified as U.S. application Ser. No. 09/237,851, entitled “ULTRASONIC RANGING SYSTEM AND METHOD FOR IMPROVING ACCURACY THEREOF,” to Songnian Li.
REFERENCES:
patent: 4578783 (1986-03-01), Iwata et al.
patent: 5943295 (1999-08-01), Varga et al.
Delphi Technologies Inc.
Funke Jimmy L.
Pihulic Daniel T.
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