Abstract:
A radio frequency identification (RFID) system with separately located transmitters and receivers which lowers system cost. The system includes a plurality of transmitters for interrogating radio frequency identification tags attached to items on store shelves, a plurality of receivers separately located from the transmitters for receiving response information from the radio frequency identification tags.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to retail transaction systems and, in particular, to a radio frequency identification (RFID) system with separately located transmitters and receivers. 
     RFID technology provides an alternative to bar code reader technology for distinguishing and recording items for purchase. RFID may result in labor savings to retailers, since it may obsolete conventional methods of identifying products. 
     Some of the uses of RFID technology are disclosed in U.S. Pat. No. 6,019,394 assigned to the assignee of the present invention. This patent is hereby incorporated by reference. 
     RFID tags may be permanently attached to products. RFID tags permanently attached to clothing and other items may be worn or carried by customers into stores. These RFID tags may be detected by RFID interrogators within the stores. 
     RFID systems that are currently being developed include an integrated unit containing uplink and downlink circuitry. The uplink and downlink circuitry sends a downlink transmission signal with sufficient energy to stimulate RFID tags, and receives an uplink signal containing responses from the tags. 
     Since the uplink signal is of significantly less energy than the downlink signal, the integrated unit must be placed close enough to the RFID tags to be able to receive the uplink signal. In a store with multiple intergrated units, placement of integrated units close enough to the RFID tags causes a redundancy in downlink signals and an excess of radio frequency (RF) energy. 
     It would be desirable to provide an RFID system with separately located transmitters and receivers. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, a radio frequency identification (RFID) system with separately located transmitters and receivers is provided. 
     The system includes a plurality of transmitters for interrogating radio frequency identification tags attached to items on store shelves, a plurality of receivers separately located from the transmitters for receiving response information from the radio frequency identification tags. 
     It is accordingly an object of the present invention to provide an RFID system with separately located transmitters and receivers. 
     It is another object of the present invention to reduce the number of transmitters in an RFID system. 
     It is another object of the present invention to provide an RFID system with separately located transmitters and receivers in which the receivers are located with electronic shelf labels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a block diagram of a first embodiment of a radio frequency identification (RFID) system; 
         FIG. 1B  is an example map of a transaction establishment incorporating the system of  FIG. 1A ; 
         FIG. 2A  is a block diagram of a second embodiment of an RFID system; 
         FIG. 2B  is an example map of a transaction establishment incorporating the system of  FIG. 2A ; and 
         FIG. 3  is a flow diagram illustrating a method of capturing information during a check transaction. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIGS. 1A and 1B , transaction system  10  primarily includes server  12 , transmitters  14 , receivers  16 , and radio frequency identification (RFID) tags  18 . 
     Server  12  executes RFID system control software  22  which controls transmitters  14  and receivers  16 . RFID system control software  22  causes transmitters  14  to transmit signals for interrogating RFID tags  18 . RFID system control software  22  receives response information from receivers  16 . 
     Server  12  may be a back office serve that also executes other applications, such as transaction software  24  and inventory management software  26 . 
     Transaction software  24  provides price information to point of sale (POS) terminal  30 . 
     Inventory management software  24  monitors shelf inventory levels using the response information from receivers  16  and product sales information from POS terminal  30 , and may automatically reorder products when inventory thresholds are reached. 
     Transmitters  14  transmit signals for interrogating RFID tags  18 . Transmitters  14  are preferably mounted to a ceiling, in rows between shelves for optimal interrogation. 
     Receivers  16  receive response information from RFID tags  18 . Receivers  16  are preferably mounted to the ceiling, in rows above corresponding shelves. 
     Transmitters  14  and receivers  16  and separately located. The number of transmitters  14  required to cover a store is generally smaller than the number of receivers  16 , since receivers  16  must be closer to items  20 . The number of transmitters  14  may be as little as half the number of receivers  16 . 
     RFID tags  18  store information, such as a unique identification code. RFID tags  18  radiate a signal containing the unique identification code using energy received from the signal from transmitter  14 . 
     Referring now to  FIGS. 2A and 2B , a second embodiment is similar to the first embodiment in  FIG. 1A , except that receivers  16  are located within electronic shelf labels (ESLs)  36 . 
     Control circuitry  40  within receiver  16  stores response information from RFID tags  18  in memory  42 . 
     RFID tag control software  22  obtains the response information through ESL management system  38 . RFID tag control software  22  causes ESL management system  38  to send message to ESLs  36  requesting response information stored within memories  42 . Control circuitry  40  receives the message and complies with instructions in the message to obtain the response information from memory  42  and send it to ESL management system  38 . 
     Control circuitry  40  also controls display of price and promotion information by ESL  36 . Communication between ESL  36  and ESL management system  38  may be wired or wireless communication. 
       FIG. 3  is a flow diagram illustrating a method of capturing information from RFID tags  18  in a system  10  of  FIGS. 2A and 2B  beginning with Start  50 . 
     In step  52 , RFID tag control software  22  activates transmitters  14 . The signal from transmitters  14  stimulate RFID tags  18  to respond with information stored inside. 
     In step  54 , receivers  16  receive signals containing the information stored within RFID tags  18 . 
     In step  56 , control circuitry  40  stores the information in memory  40  within ESL  36 . 
     In step  58 , RFID tag control software  22  causes ESL management system  38  to send a message to ESL  36  to obtain the information. 
     In step  60 , control circuitry  40  receives the message, retrieves the information from memory  42 , and sends it to ESL management system  38 . 
     In step  62 , ESL management system  38  sends the information to RFID tag control software  22 . 
     In step  64 , operation ends. 
     Advantageously, overall cost of system  10  is lower than a system with integrated transmitter  14  and receiver  16 . Regulatory requirements may favor separation as well, since the overall amount of RF energy being transmitted may be lowered using fewer, more powerful transmitters  14  versus many less powerful integrated transmitters  14 . The installation cost could be substantially impacted as a separate transmitter  14  may be powered separately by a alternating current (AC) source, while receiver  16  may be battery powered. Separation of power supplies facilitates system flexibility. Receivers  16  may be placed in various locations, regardless of the availability of external power. Separation of power supplies also facilitates incorporation into battery powered ESLs  38 . 
     Although the invention has been described with particular reference to certain preferred embodiments thereof, variations and modifications of the present invention can be effected within the spirit and scope of the following claims.