US Patent Issued on November 26, 1991 http://www.patentstorm.us/patents/5068669-description.html

BACKGROUND OF THE INVENTION

The present invention relates in general to the transfer of energy by means of electromagnetic waves to power a remote device. More specifically, the present invention relates to a system for "power beaming" energy from a source at high frequencies and rectifying such energy to provide a source of DC energy to a remote device.


Identification/security tag system employing electronic doppler shifting and/or rectenna structure

Document Type and Number: United States Patent 5416486

Link to this Page: http://www.freepatentsonline.com/5416486.html

Abstract: An identification/security tag system, including miniaturized tags which can be readily concealed, utilizes a concept of "electronic" Doppler shifting to generate a frequency shifted signal in response to an interrogation signal. The frequency shifted signal is used to identify individual tags. The implementation of electronic Doppler shifting permits the utilization of conventional police/sport radar guns as a combined transmitter and receiver unit, thereby greatly reducing the expense of the system. The high frequency operation of the system permits size of the tag to be significantly reduced with respect to the size of tags used in conventional tag systems. Rectenna circuitry is further employed to eliminate the need for an active power supply in the tag in some applications.

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