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. 30, 1991
Filed:
May. 26, 1989
Philip R Troyk, Morton Grove, IL (US);
Glenn A DeMichele, Chicago, IL (US);
Trovan Limited, Isle of Man, GB;
Abstract
An electromagnetic transmission and detection apparatus comprising a transmission coil (20) for producing a high intensity electromagnetic field including one or more conductive windings (24) circumscribing a substantially polygonal volume of space having a central axis, and first and second receiver coils (22) disposed within the polygonal volume of space for receiving a low-intensity electromagnetic field transmitted from an external source. The receiver coils (22) are co-planar with the transmitter coil (20) and are disposed within the polygonal volume of the transmitter coil at positions which are polygonally, diametrical opposed to one another. The receiver coils (22) are electrically connected to each other in a differential circuit relationship such that the magnitude of electrical signals induced in the receiver coils (22) by uniform electromagnetic energy are substantially equal and opposite to one another. The differential circuit is operative to substract the electrical signals induced in the receiver coils and output a differential output signal, which is at a minimum when the two receiver coils receive approximately equal quantities of energy and is at a maximum when one of the receiver coils receives more electromagnetic energy from the external source than the other receiver coil. A display device (19) receives the differential output signal and displays a measure of the identification signal when the differential output signal is at a maximum.