Transponder system with variable frequency transmission
First Claim
1. An electronic identification system comprising:
- a) means for generating an electromagnetic excitation field at a first frequency settable to a plurality of different frequencies;
b) portable transponder means including means for storing variable identification data, and means for detecting ingress of said portable transponder means into said electromagnetic excitation field and in response transmitting at a second frequency settable to a plurality of different frequencies an informational signal containing said data, said transmitting of said signal being independent of said transponder means remaining in said field, said second frequency being neither derived from nor related to said first frequency of the electromagnetic excitation field, and said first and second frequencies remaining constant during transmission of said information signal; and
c) means for receiving said informational signal and in response generating an output signal representing said variable identification data contained in said informational signal.
6 Assignments
0 Petitions
Accused Products
Abstract
An electronic identification system comprising a transmitter for generating an electromagnetic excitation signal, one or more portable transponders for storing variable identification data, and for transmitting an information signal containing the identification data upon entering the field. Transmission of the information signal is independent of the excitation signal in both time and frequency. A radio frequency receiver is provided for receiving the information signal and in response generating output signal representing the variable identification data contained in the information signal. The system overcomes two principle disadvantages associated with existing systems: and excitation frequency can be selected for optimum performance given the circumstances dictated by each application; an independent response channel can be selected according to the requirements of each installation or application, thereby allowing response signals to be transmitted by transponders at a frequency which differs form the frequency of an interfering signal.
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Citations
21 Claims
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1. An electronic identification system comprising:
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a) means for generating an electromagnetic excitation field at a first frequency settable to a plurality of different frequencies; b) portable transponder means including means for storing variable identification data, and means for detecting ingress of said portable transponder means into said electromagnetic excitation field and in response transmitting at a second frequency settable to a plurality of different frequencies an informational signal containing said data, said transmitting of said signal being independent of said transponder means remaining in said field, said second frequency being neither derived from nor related to said first frequency of the electromagnetic excitation field, and said first and second frequencies remaining constant during transmission of said information signal; and c) means for receiving said informational signal and in response generating an output signal representing said variable identification data contained in said informational signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification