Rfid interrogator device

Abstract

An RFID interrogator device has a transmission section for transmitting a command to an RFID tag and a reception section for receiving an RF signal from the RFID tag and is configured to perform backscatter radio communication with the RFID tag. The RFID interrogator device comprises a time window setting section configured to set a time window at timing of receiving preamble data added to a head of response data transmitted from the RFID tag in response to the command, and an identifying data storage section storing preamble identifying data. The RFID interrogator device compares the data received within the time window, with preamble identifying data stored in the identifying data storage section, thereby determining whether the data received is identical to the preamble data transmitted from the RFID tag.

1 . An RFID interrogator device, transmitting a command to an RFID tag and receiving response data from the RFID tag after a predetermined lapse of time, comprising:
 a time window setting section configured to set a time window at timing of receiving preamble data added to a head of response data transmitted from the RFID tag in response to the command;   an identifying data storage section configured to store preamble identifying data; and   decision means for comparing data received within the time window, with preamble identifying data stored in the identifying data storage section, thereby determining whether the data received is identical to the preamble data transmitted from the RFID tag.   
   
   
       2 . The RFID interrogator device according to  claim 1 , wherein the time window setting section sets the time window at timing of receiving prescribed lower bits of the preamble data. 
   
   
       3 . The RFID interrogator device according to  claim 2 , wherein the time window is set in accordance with a sampling cycle and the number of bits constituting the preamble identifying data. 
   
   
       4 . The RFID interrogator device according to  claim 3 , wherein the time window is assigned with a time based on maximum and minimum values preset for a predetermined response time of the RFID tag. 
   
   
       5 . The RFID interrogator device according to  claim 3 , wherein the time window is assigned with a time equivalent to a difference between maximum and minimum values preset for a predetermined response time of the RFID tag. 
   
   
       6 . The RFID interrogator device according to  claim 5 , wherein the time window starts at a sum of a time that elapses until the preamble data is received from the RFID tag after the RFID interrogator device has transmitted the command and a time obtained by multiplying the sampling cycle by a difference between the number of preamble data bits and the number of preamble identifying data bits. 
   
   
       7 . The RFID interrogator device according to  claim 2 , wherein the time window starts at a sum of a time that elapses until the preamble data is received from the RFID tag after the RFID interrogator device has transmitted the command and a time obtained by multiplying the sampling cycle by a difference between the number of preamble data bits and the number of preamble identifying data bits. 
   
   
       8 . The RFID interrogator device according to  claim 1 , wherein the time window starts at a sum of a time that elapses until the preamble data is received from the RFID tag after the RFID interrogator device has transmitted the command and a time obtained by multiplying the sampling cycle by a difference between the number of preamble data bits and the number of preamble identifying data bits. 
   
   
       9 . The RFID interrogator device according to  claim 1 , wherein the decision means determines whether the data received is identical to the preamble identifying data, determines again whether the data received is identical to the preamble identifying data, when the data received is determined not to be identical to the preamble identifying data, and terminates reading of data from the RFID tag when the data received is again determined not to be identical to the preamble identifying data. 
   
   
       10 . The RFID interrogator device according to  claim 1 , wherein the decision means determines that the data received is preamble data when an inverted pattern of the preamble identifying data is detected from the data received, within the time window. 
   
   
       11 . The RFID interrogator device according to  claim 1 , wherein the decision means is a comparator. 
   
   
       12 . The RFID interrogator device according to  claim 1 , further comprising:
 a phase-locked loop device configured to supply a local carrier signal to the transmission section for transmitting the command;   a phase shifter configured to phase shift, by 90°, the local carrier signal supplied from the phase-locked loop device;   a first mixer configured to mix a signal received from the RFID tag with the local carrier signal supplied from the phase-locked loop device, thereby generating an I-signal that is in phase with the local carrier signal; and   a second mixer configured to mix the signal received from the RFID tag with the local carrier signal phase shifted by 90° by the phase shifter, thereby generating a Q-signal that is an component orthogonal to the local carrier signal.   
   
   
       13 . The RFID interrogator device according to  claim 12 , wherein the time window setting section, the identifying data storage section and the decision means are provided to process the I-signal, and another time window setting section, another identifying data storage section and another decision means are provided to process the Q-signal. 
   
   
       14 . A radio communication method of an RFID interrogator device, transmitting a command to an RFID tag and receiving response data from the RFID tag after a predetermined lapse of time, comprising:
 setting a time window at timing of receiving preamble data added to a head of response data transmitted from the RFID tag in response to the command;   setting the prescribed lower bits of preamble data as preamble identifying data; and   comparing data received within the time window with the preamble identifying data, thereby determining whether the received data is identical to the preamble data transmitted from the RFID tag.   
   
   
       15 . The radio communication method of the RFID interrogator device according to  claim 14 , wherein the time window is set at timing of receiving prescribed lower bits of the preamble data. 
   
   
       16 . The radio communication method of the RFID interrogator device according to  claim 14 , wherein the time window starts at a sum of a time that elapses until the preamble data is received from the RFID tag after the RFID interrogator device has transmitted the command and a time obtained by multiplying the sampling cycle by a difference between the number of preamble data bits and the number of preamble identifying data bits. 
   
   
       17 . The radio communication method of the RFID interrogator device according to  claim 14 , wherein the time window is set in accordance with a sampling cycle and the number of bits constituting the preamble identifying data. 
   
   
       18 . The radio communication method of the RFID interrogator device according to  claim 17 , wherein the time window is assigned with a time equivalent to a difference between maximum and minimum values preset for a predetermined response time of the RFID tag.