RFID Beam Forming System

Abstract

A multi-protocol, multi-band array antenna system may be used in Radio Frequency Identification (RFID) system reader and sensory networks. The antenna array may include array elements with an integrated low noise amplifier. The system may employ digital beam forming techniques for transmission and steering of a beam to a specific sensor tag or group of tags in a cell. The receive beam forming network is optimized for detecting signals from each sensor tag. Narrow and wideband interferences may be excised by an interference nulling algorithm. Space division multiplexing may be used by the antenna system to enhance system processing capacity.

1 . An RFID system, comprising:
 a plurality of antenna elements;   a transmit module configured to transmit RFID tag interrogation signals to an RFID tag using antenna elements of the plurality of antenna element by adjusting relative phases of the RFID tag interrogation signals;   a receiver module configured to process at least one backscattered sequence of RFID tag information received by at least one antenna element from the RFID tag to derive information from the backscattered signal; and   a scheduler configured to modify RFID tag interrogation signals fed to each of a set of antenna elements of the plurality of antenna elements to maximize the power of the output at a given spatial location.   
     
     
         2 . The RFID system of  claim 1 , wherein the plurality of antenna elements are a part of a distributed antenna array. 
     
     
         3 . The RFID system of  claim 1 , wherein the plurality of antenna elements are distributed across a plurality of antenna arrays. 
     
     
         4 . The RFID system of  claim 1 , wherein the plurality of antenna elements are a part of a phased antenna array. 
     
     
         5 . The RFID system of  claim 1 , wherein the transmit module and the receiver module are further configured to iterate the transmitting, processing, and deriving to further reduce relative phase. 
     
     
         6 . The RFID system of  claim 1 , wherein the transmit module is further configured to adjust relative phases of the RFID tag interrogation signals in the baseband prior to digital to analog conversion by a digital to analog converter. 
     
     
         7 . The RFID system of  claim 1 , wherein the scheduler is further configured to perform space division multiplexing by varying beamforming coefficients. 
     
     
         8 . The RFID system of  claim 1 , wherein a first antenna element includes two ports, wherein exciting a first of the two ports generates a left-hand circular polarized radiated field and exciting a second of the two ports generates a right-hand circular polarized radiated field. 
     
     
         9 . The RFID system of  claim 8 , wherein a first of the two ports is utilized to transmit an RFID tag interrogation signal and a second of the two ports is utilized to receive a backscattered signal. 
     
     
         10 . The RFID system of  claim 1 , wherein a first antenna element of the antenna elements is configured to transmit an RFID tag interrogation signal having a first polarization and a second antenna element of the antenna elements is configured to transmit an RFID tag interrogation signal having a different second polarization. 
     
     
         11 . The RFID system of  claim 1 , wherein the scheduler selects a polarization with which each of the set of antenna element transmits an RFID tag interrogation signal. 
     
     
         12 . The RFID system of  claim 1 , wherein the scheduler is configured to employ a spatial hopping pattern that randomly selects cells to illuminate. 
     
     
         13 . A method for deriving information from an RFID tag, comprising:
 modifying RFID tag interrogation signals to be transmitted by each of a set of antenna elements of a plurality of antenna elements to maximize the power of the output at a given spatial location of the RFID tag;   transmitting RFID tag interrogation signals from the plurality of antenna elements to the RFID tag by adjusting relative phases of the RFID tag interrogation signals;   receiving at least one backscattered sequence of RFID tag information from the RFID tag by at least one antenna element; and   deriving information from the backscattered signal.   
     
     
         14 . The method of  claim 13 , wherein the set of antenna elements are part of a distributed antenna array. 
     
     
         15 . The method of  claim 13 , wherein the set of antenna elements are part of a phased antenna array. 
     
     
         16 . The method of  claim 13  further comprising iterating the modifying, transmitting, receiving, and deriving to further reduce relative phase. 
     
     
         17 . The method of  claim 13  further comprising performing space division multiplexing by varying the modifications to the RFID tag interrogation signals. 
     
     
         18 . The method of  claim 13 , wherein a first antenna element of the antenna elements is configured to transmit an RFID tag interrogation signal having a first polarization and a second antenna element of the antenna elements is configured to transmit an RFID tag interrogation signal having a different second polarization. 
     
     
         19 . The method of  claim 13 , wherein transmitting the RFID tag interrogation signals comprises selecting a polarization with which each antenna element of the set of antenna element transmits an RFID tag interrogation signal. 
     
     
         20 . The method of  claim 13 , wherein transmitting RFID tag interrogation signals comprises transmitting the RFID tag interrogation signals in a spatial hopping pattern that randomly selects cells to illuminate.