System and method of determining short range distance between RF equipped devices
First Claim
1. A method of automatically determining the distance between a first RF equipped device and a second RF equipped device comprising:
- establishing a radio link between said first RF equipped device and said second RF equipped device;
in said first RF equipped device;
creating an acoustic waveform in the form of first digital audio samples;
transmitting said first digital audio samples via said radio link;
converting said first digital audio samples to an analog audio waveform;
emitting said analog audio waveform as an acoustic signal via a loudspeaker;
in said second RF equipped device;
receiving said first digital audio samples via said radio link;
receiving said acoustic signal via a microphone;
converting said received acoustic signal to second digital audio samples; and
determining the time difference between the arrival of said first digital audio samples and said acoustic signal; and
determining the distance between said first RF equipped device and said second RF equipped device based on the known speed of propagation of radio waves, the known speed of sound, and the time difference between the arrival of said first digital audio samples and said acoustic signal.
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Accused Products
Abstract
A first, transmitting, device transmits a digitized data message using a short range radio link followed by digital data representing a digitized acoustic signal, such as a tone. Simultaneously, or with a predetermined time delay, the transmitting device emits an acoustic version of the same signal using an acoustic transducer such as a loudspeaker. A second, receiving, device receives the data message and the digitized acoustic signal via the short range radio link and receives the acoustic version of the signal via a microphone, which converts the acoustic signal to a second digitized version of the acoustic signal. Digital signal processing circuits then correlate the second digitized signal received acoustically with the digitized acoustic signal received over the short range radio link to determine a time difference of arrival. The time difference is corrected for any predetermined delay between the radio and the acoustic signal emissions at the transmitter and predetermined processing delays in the receiver. Once the time delay is determined, the receiving device can determine its distance from the transmitting device using the difference between the speed of sound and the speed of radio propagation.
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Citations
14 Claims
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1. A method of automatically determining the distance between a first RF equipped device and a second RF equipped device comprising:
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establishing a radio link between said first RF equipped device and said second RF equipped device;
in said first RF equipped device;
creating an acoustic waveform in the form of first digital audio samples;
transmitting said first digital audio samples via said radio link;
converting said first digital audio samples to an analog audio waveform;
emitting said analog audio waveform as an acoustic signal via a loudspeaker;
in said second RF equipped device;
receiving said first digital audio samples via said radio link;
receiving said acoustic signal via a microphone;
converting said received acoustic signal to second digital audio samples; and
determining the time difference between the arrival of said first digital audio samples and said acoustic signal; and
determining the distance between said first RF equipped device and said second RF equipped device based on the known speed of propagation of radio waves, the known speed of sound, and the time difference between the arrival of said first digital audio samples and said acoustic signal. - View Dependent Claims (2, 3, 4, 5)
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6. In an RF equipped device, a method of automatically determining the distance between said RF equipped device and a second RF equipped device, said second RF equipped device capable of emitting an acoustic signal and transmitting a radio signal, said method comprising:
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receiving first digital audio samples via a radio link;
receiving an acoustic signal via a microphone;
converting said received acoustic signal to second digital audio samples; and
determining the time difference between the arrival of said first digital audio samples and said acoustic signal; and
determining the distance from said second RF equipped device based on the known speed of propagation of radio waves, the known speed of sound, and the time difference between the arrival of said first digital audio samples and said acoustic signal. - View Dependent Claims (7, 8)
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9. An RF equipped device capable of automatically determining the distance between itself and a second RF equipped device wherein said second RF equipped device emits an acoustic signal and transmits a corresponding radio signal, said RF equipped device comprising:
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an RF module that receives first digital audio samples via a radio link;
a microphone that receives an acoustic signal;
a CODEC that converts said received acoustic signal to second digital audio samples; and
a processor that;
determines the time difference between the arrival of said first digital audio samples and said acoustic signal; and
determines the distance from said second RF equipped device based on the known speed of propagation of radio waves, the known speed of sound, and the time difference between the arrival of said first digital audio samples and said acoustic signal. - View Dependent Claims (10, 11)
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12. In an RF equipped device, a computer program product that automatically determines the distance between itself and a second RF equipped device, said second RF equipped device capable of emitting an acoustic signal and transmitting a radio signal, the computer program product having a medium with a computer program embodied thereon, the computer program product comprising:
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computer program code for receiving first digital audio samples via a radio link;
computer program code for receiving an acoustic signal via a microphone;
computer program code for converting said received acoustic signal to second digital audio samples; and
computer program code for determining the time difference between the arrival of said first digital audio samples and said acoustic signal; and
computer program code for determining the distance from said second RF equipped device based on the known speed of propagation of radio waves, the known speed of sound, and the time difference between the arrival of said first digital audio samples and said acoustic signal. - View Dependent Claims (13, 14)
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Specification