Patent ID: 7978051

Claim:
An RFID interrogator device, transmitting query data to an RFID tag and receiving response data from the RFID tag after lapse of predetermined time, comprising: a time window setting section configured to set a time window at timing of receiving predetermined lower bits of preamble data added to a head of response data transmitted from the RFID tag; an identifying data setting section configured to set the predetermined lower bits of preamble data as preamble identifying data; and decision means for comparing data received within a range of the time window set by the time window setting section, with preamble identifying data set by the identifying data setting section, thereby determining whether the data received is identical to the preamble data transmitted from the RFID tag; wherein the time window setting section sets the time window to start at a sum of a time that elapses until the preamble data is received from the RFID tag and a time obtained by multiplying a sampling cycle by a difference between the number of preamble data bits and the number of preamble identifying data bits.