Proximity identification system with flux concentration in operating region

• US 5,159,332 A
• Filed: 03/14/1991
• Issued: 10/27/1992
• Est. Priority Date: 06/05/1989
• Status: Expired due to Fees

• Current Assignee: Charles A. Walton
• Original Assignee: Charles A. Walton
• Inventors: Walton, Charles A.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Holloway, III, Edwin C.
• Application Number:
  US07/670,359
• Time in Patent Office: 593 Days
• Field of Search: 340/825.54, 340/825.34, 340/825.63, 340/825.64, 340/825.65, 340/825.69, 340/825.72, 340/825.3, 340/572, 340/573, 340/905, 340/933, 340/941, 455/41, 455/129, 343/787, 343/788
• US Class Current: 340/10.3
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal

Abstract

A proximity identification system incorporating ferrite rods. The rods are used in both the reader and the tag and additional rods may be used to strengthen and concentrate the flux field in the regions near the reader to obtain better performance in such regions. A coding system requiring minimum power for the tag is also described.

Claims

1. A proximity identification system comprising:

a reader antenna comprising at least one coil wound around each of a group of four ferrite rods in a diamond-shaped pattern and polarized and placed so as to generate strong diagonal and lateral flux lines within said diamond-shaped pattern;

a reader section having a reader circuit means connected to the reader antenna for simultaneously supplying a power signal to the reader antenna and detecting an identifier signal, said reader circuit means comprising;

(a) an oscillator connected to a power amplifier connected to the reader antenna for generating said power signal, (b) a detector means connected to the reader antenna for detecting said identifier signal, and (c) an amplifier to convert said detected signals to pulses; and

an identifier tag section having an identifier antenna formed of a ferrite rod with a winding, and an identifier circuit means connected to the winding for generating an identifier signal for modulating the impedance of the tag winding with the modulation changing the flux field around the tag antenna and the changing flux field also changing the flux in the reader antenna when said identifier antenna is disposed within said diagonal flux lines generated by the reader antenna.

2. A proximity identification system comprising:

an identifier tag having means to emit an identifying signal in response to an excitation energy and including a ferrite rod antenna with a winding;

a reader antenna connected to radiate excitation energy to the tag and shaped to concentrate a flux field in manner favorable to excitation of the tag;

a reader electronic section having means to power the reader antenna, means to detect and amplify emissions from the identifier tag, and means to report the emissions to a computer;

the reader antenna being formed in a diamond arrangement of four ferrite rods having windings that are wound on said rods for polarizing said rods in a manner that creates the greatest intensity of said external flux about a diagonal line in the center of said diamond arrangement, and

the identifier tag is situated at the center of said diamond arrangement and said rod antenna is aligned with said diagonal line, so that said identifying signal from the identifier has maximum favorable excitation of the tag.