Method and apparatus for improving the efficiency and accuracy of rfid systems

Abstract

The present invention relates to a method and apparatus for transmitting a narrow signal beam that allows the precise location of RFID tags to be determined and reduces tag collisions. The present invention further relates to a method and apparatus for combing an RFID reader with an optical source to visualize the interrogation zone of the reader. The present invention also relates to a method and apparatus for improving the efficiency of RFID systems.

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       27 . A method for improving the efficiency of RFID systems having RFID readers and RFID tags, comprising the steps of:
 employing an antenna array by an RFID reader,   broadcasting a data signal using said antenna array,   broadcasting a scramble signal using said antenna array, and   adjusting array excitation coefficients of said antenna array for said data signal and said scramble signal such that said scramble signal overshadows said data signal in all but selected regions.   
   
   
       28 . The method of  claim 27 , wherein said antenna array employs patch antennas. 
   
   
       29 . The method of  claim 27 , further comprising the step of employing three antenna elements by said RFID reader, wherein two antenna elements transmit said scramble signal and one antenna element interrogates RFID tags. 
   
   
       30 . The method of  claim 27 , further comprising the step of adjusting the array excitation coefficients for said data signal and said scramble signal to create an interrogation beam that fits an opening in a container. 
   
   
       31 . The method of  claim 27 , further comprising the step of employing an antenna, wherein said antenna transmits two or more interrogation beams and wherein any of said RFID tags in said interrogation zone receive sufficient power to operate from at least one of said two or more interrogation beams. 
   
   
       32 . The method of  claim 27 , further comprising the step of employing two or more scramble signals, wherein said two or more scramble signals prevent leakage of said data signal. 
   
   
       33 . The method of  claim 32 , wherein two or more scramble signals employ coefficients that are mirror images. 
   
   
       34 . The method of  claim 27 , further comprising the step of transmitting said data signal and said scramble signal adjusted to create closely spaced disjoint interrogation zones. 
   
   
       35 . The method of  claim 27 , wherein the position of said RFID reader is determined from the solution of an inverse source problem. 
   
   
       36 . The method of  claim 35 , wherein the inverse source problem is solved with an iterative optimization scheme. 
   
   
       37 . The method of  claim 27 , wherein the position of said RFID reader is determined from measurements. 
   
   
       38 . The method of  claim 27 , wherein the array excitation coefficients are determined from the solution to an inverse source problem. 
   
   
       39 . The method of  claim 38 , wherein the inverse source problem is solved with an iterative optimization scheme. 
   
   
       40 . The method of  claim 27 , wherein the array excitation coefficients are determined from measurements. 
   
   
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