Electronic proximity identification system with simplified low power identifier
First Claim
1. An identification system comprising:
- a reader,a portable identifier,said reader including;
a first signal generator for operating a first signal,a first antenna connected to radiate said first signal, andsaid portable identifier including;
a second antenna mutually coupled to said first antenna to receive radiation power from said first antenna and to send signals to said first antenna,a data generating circuit powered by said radiation power; and
a circuit causing said data to modulate the electrical properties of said second antenna, and through said mutual coupling thereby affect the electrical properties of said first antenna, andsaid reader further containing a circuit for detecting changes in said electrical properties of said first antenna to thereby identify said portable identifier by detecting said data.
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Accused Products
Abstract
An identification system comprising a reader (10) including a first signal generator (12) for generating a first signal (F1) which is radiated by an antenna (17). An identifier (11) includes an antenna (20) receiving the first signal for transmission to a signal modulator (32) which operates to modulate the 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 and consequent voltage on the reader antenna (17). By detecting the change in the voltage on the reader antenna the code of the identifier is determined. Power drain is minimized and power is used efficiently by unloading during modulation and by changing reactance without changing load.
117 Citations
10 Claims
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1. An identification system comprising:
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a reader, a portable identifier, said reader including; a first signal generator for operating a first signal, a first antenna connected to radiate said first signal, and said portable identifier including; a second antenna mutually coupled to said first antenna to receive radiation power from said first antenna and to send signals to said first antenna, a data generating circuit powered by said radiation power; and a circuit causing said data to modulate the electrical properties of said second antenna, and through said mutual coupling thereby affect the electrical properties of said first antenna, and said reader further containing a circuit for detecting changes in said electrical properties of said first antenna to thereby identify said portable identifier by detecting said data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification