Radio frequency identification reader antenna arrangement with multiple linearly-polarized elements

Abstract

An antenna method and apparatus for a Radio Frequency Identification (RFID) reader includes an RFID reader, a plurality of radio ports of the RFID reader, and a plurality of linearly polarized antenna elements coupled to the radio ports, wherein the RFID reader directs the radio ports to sequentially communicatively connect only one antenna element at a time to the RFID reader such that only one antenna element is operable to transmit/receive at any instant in time. The antenna elements are mounted in an alternating vertically polarized and horizontally polarized configuration.

What is claimed is: 
     
         1 . An antenna apparatus for a Radio Frequency Identification (RFID) reader, comprising:
 an RFID reader;   a plurality of radio ports coupled to the RFID reader; and   a plurality of linearly polarized antenna elements coupled to the radio ports,   wherein the RFID reader directs the radio ports to sequentially communicatively connect only one antenna element at a time to the RFID reader such that only one antenna element is operable to transmit/receive at any instant in time.   
     
     
         2 . The antenna apparatus of  claim 1 , wherein there is an even number of antenna elements arranged in a circle to radiate outwardly from the circle. 
     
     
         3 . The antenna apparatus of  claim 2 , wherein there are eight antenna elements evenly disposed at 45 degree intervals of the circle, each with a gain of 6 dB. 
     
     
         4 . The antenna apparatus of  claim 2 , wherein the antenna elements are linearly polarized to provide either of a first polarization and a second polarization ninety degrees to the first polarization, and wherein the antenna elements alternate polarizations around the circle. 
     
     
         5 . The antenna apparatus of  claim 4 , wherein each antenna element provides an antenna gain that is down 3 dB (half power) at about ±46.5 degrees from its bore sight, such that RFID read coverage areas of neighboring antenna elements do not significantly overlap. 
     
     
         6 . The antenna apparatus of  claim 4 , wherein the antenna elements with the first polarization have a first angular tilt with respect to a ceiling and the antenna elements with the second polarization have a second angular tilt with respect to the ceiling different from the first angular tilt. 
     
     
         7 . The antenna apparatus of  claim 6 , wherein the first polarization is a vertical polarization and the second polarization is a horizontal polarization, and wherein the first angular tilt is greater than the second angular tilt such that the vertically polarized antenna elements are directed more downwardly from the ceiling than the horizontally polarized antenna elements. 
     
     
         8 . The antenna apparatus of  claim 1 , wherein each antenna element comprises a linearly polarized, full wavelength loop element oriented between, and parallel to, a director plate and a reflector panel. 
     
     
         9 . The antenna apparatus of  claim 8 , wherein the reflector panels of the antenna elements are joined together to define a common reflector box, wherein the reflector box defines a housing that contains the radio ports of the RFID reader and acts as an electrical ground for electrical components in the box. 
     
     
         10 . A Radio Frequency Identification (RFID) reader, comprising:
 a fixed overhead housing containing the RFID reader;   a plurality of radio ports disposed within the housing; and   an antenna apparatus disposed outside of the housing and coupled to provide communications to the RFID reader via the radio ports, wherein the antenna apparatus comprises:
 a plurality of linearly polarized antenna elements coupled to the radio ports, 
 wherein the RFID reader directs the radio ports to sequentially communicatively connect only one antenna element at a time to the RFID reader such that only one antenna element is operable to transmit/receive at any instant in time. 
   
     
     
         11 . A method for reading Radio Frequency Identification (RFID) tags with a fixed overhead RFID reader, the method comprising the steps of:
 providing a plurality of linearly polarized antenna elements;   sequentially communicatively connecting only one antenna element at a time to the RFID reader such that only one antenna element is operable to transmit/receive at any instant in time; and   reading RFID tags within an RFID read coverage area of each sequenced antenna element.