Rfid system and communication method performed by the same

Abstract

Provided is an RFID system and method for maintaining a constant strength of a signal transmitted from an RFID tag to an RFID reader, regardless of a distance between the reader and tag. The RFID signal strength measuring reader measures a signal strength received from the RFID tag, creates control information used to set an amplification amount of the RFID tag by using a value of the measured strength to include the control information in an output signal, and sends the output signal to the RFID tag. The RFID tag, if the signal sent from the RFID reader is received, extracts internal information from the received signal, sends the information to the RFID reader as an output signal, and extracts the control information included in the signal sent from the RFID reader to adjust a strength of the output signal according to a value of the control information.

What is claimed is: 
     
         1 . A radio frequency communication system comprising:
 a first device configured to transmit a wireless signal; and   a second device configured to receive the wireless signal and generate control information based on strength of the received wireless signal, and send the control information to the first device;   wherein the second device sends the control information including a digital value to the first device, and the first device, if the control information sent from the second device is received, extracts the digital value from the control information, and adjusts transmission power of the wireless signal based on the digital value contained within the control information.   
     
     
         2 . The radio frequency communication system of  claim 1 , wherein the second device measures strength of the received wireless signal and generates the control information based on the measured value of the strength of the received wireless signal. 
     
     
         3 . The radio frequency communication system of  claim 1 , if the strength of the wireless signal transmitted from the first device to the second device is below a first predetermined value, the second device sets the digital value of the control information so that the amplification amount of the first device is increased. 
     
     
         4 . The radio frequency communication system of  claim 1 , if the strength of the wireless signal transmitted from the first device to the second device is above a second predetermined value, the second device sets the digital value of the control information so that the amplification amount of the first device is reduced. 
     
     
         5 . The radio frequency communication system of  claim 1 , if the strength of the wireless signal transmitted from the first device to the second device is below a first predetermined value, the second device sets the digital value of the control information so that the amplification amount of the first device is increased, and
 if the strength of the wireless signal transmitted from the first device to the second device is above a second predetermined value, the second device sets the digital value of the control information so that the amplification amount of the first device is reduced.   
     
     
         6 . The radio frequency communication system of  claim 1 , wherein the second device measures a strength of the received wireless signal and generates the control information based on the measured value of the strength of the received wireless signal. 
     
     
         7 . The radio frequency communication system of  claim 6 , wherein the second device generates the control information by comparing the measured value and at least one predetermined target value. 
     
     
         8 . The radio frequency communication system of  claim 7 , wherein the control information includes an error value representing a difference between the measured value and the predetermined target value. 
     
     
         9 . The radio frequency communication system of  claim 1 , wherein the first device determines whether to perform the transmission of the wireless signal according to the reception of the control information. 
     
     
         10 . The radio frequency communication system of  claim 9 , wherein when the first device receives the control information the first device transmits the wireless signal, and when the first device does not receive the control information the first device does not transmit the wireless signal. 
     
     
         11 . The radio frequency communication system of  claim 10 , wherein the second device sends identification information to the first device. 
     
     
         12 . The radio frequency communication system of  claim 11 , wherein the identification information identifies the second device. 
     
     
         13 . A radio frequency communication system comprising:
 a power receiver configured to transmit a wireless signal; and   a power transmitter configured to receive the wireless signal and generate control information based on strength of the received wireless signal, and send the control information to the power receiver,   wherein the power receiver is supplied with power from a signal transmitted from the power transmitter,   wherein the power transmitter generates control information based on strength of the received wireless signal and sends the control information to the power receiver, and the power receiver controls transmission power of the wireless signal based on the received control information.   
     
     
         14 . The radio frequency communication system of  claim 13 , wherein the power transmitter sends the control information including a digital value to the power receiver, and the power receiver, if the control information sent from the power transmitter is received, extracts the digital value from the control information, and adjusts transmission power of the wireless signal based on the digital value contained within the control information. 
     
     
         15 . The radio frequency communication system of  claim 14 , if the strength of the wireless signal transmitted from the power receiver to the power transmitter is below a first predetermined value, the power transmitter sets the digital value of the control information so that the amplification amount of the power receiver is increased. 
     
     
         16 . The radio frequency communication system of  claim 14 , if the strength of the wireless signal transmitted from the power receiver to the power transmitter is above a second predetermined value, the power transmitter sets the digital value of the control information so that the amplification amount of the power receiver is reduced. 
     
     
         17 . The radio frequency communication system of  claim 14 , if the strength of the wireless signal transmitted from the power receiver to the power transmitter is below a first predetermined value, the power transmitter sets the digital value of the control information so that the amplification amount of the power receiver is increased, and
 if the strength of the wireless signal transmitted from the power receiver to the second device is above a second predetermined value, the second device sets the digital value of the control information so that the amplification amount of the power receiver is reduced.   
     
     
         18 . The radio frequency communication system of  claim 13 , wherein the power receiver determines whether to perform the transmission of the wireless signal according to the reception of the control information. 
     
     
         19 . The radio frequency communication system of  claim 18 , wherein when the power receiver receives the control information the power receiver transmits the wireless signal, and when the power receiver does not receive the control information the power receiver does not transmit the wireless signal. 
     
     
         20 . The radio frequency communication system of  claim 13 , wherein the power transmitter sends identification information to the power receiver.