Electronic proximity identification system
First Claim
1. An identification system comprising:
- a reader havinga first signal generator for generating a first signal, anda first antenna connected to said first signal generator for radiating said first signal;
an identifier havinga second antenna mutually coupled to said first antenna for receiving radiated power from said first antenna and for sending signals to said first antenna,a data-generating circuit powered by said radiated power for generating data in binary form having a selected series of first and second logic states and including transitions in logic level at the beginning and end of a short period for representing the first logic state and transitions in logic level at the beginning and end of a longer period for representing the second logic state, anda modulation circuit connected to said data generating circuit for modulating the electrical parameter of said second antenna with said data and through said mutual coupling thereby affect an electrical parameter of said first antenna; and
a detecting circuit coupled to said reader for detecting changes in said electrical parameter of said first antenna to identify said identifier by detecting said data.
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Accused Products
Abstract
An identification system in which power drain is minimized is disclosed. The system comprises a reader (10) including a first signal generator (12) for generating a first signal (F1) which is then radiated by an antenna (17). An identifier (11) is shown which includes an antenna (20) for receiving the first signal for transmission to a signal modulator (32) which operates to modulate the first signal in accordance with a preassigned code for the identifier. The modulated signal is then used to periodically unload or change the reactance of the antenna (20) which action in turn changes the reactance of the reader antenna (17) and the consequent voltage on the reader antenna. By detecting the change in the voltage on the reader antenna the code of the identifier is determined. Power is used efficiently by low frequency oscillation within the signal modulator, by unloading during modulation, and by changing circuit reactance without changing the circuit load.
82 Citations
10 Claims
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1. An identification system comprising:
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a reader having a first signal generator for generating a first signal, and a first antenna connected to said first signal generator for radiating said first signal; an identifier having a second antenna mutually coupled to said first antenna for receiving radiated power from said first antenna and for sending signals to said first antenna, a data-generating circuit powered by said radiated power for generating data in binary form having a selected series of first and second logic states and including transitions in logic level at the beginning and end of a short period for representing the first logic state and transitions in logic level at the beginning and end of a longer period for representing the second logic state, and a modulation circuit connected to said data generating circuit for modulating the electrical parameter of said second antenna with said data and through said mutual coupling thereby affect an electrical parameter of said first antenna; and a detecting circuit coupled to said reader for detecting changes in said electrical parameter of said first antenna to identify said identifier by detecting said data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification