The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 17, 1990
Filed:
Aug. 26, 1988
Charles A Walton, Los Gatos, CA (US);
France Rode, Los Altos, CA (US);
Sielox Systems, Inc., Cupertino, CA (US);
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.