RFID system
An antenna is disposed near a route of mobile object. A fixed tag is disposed at a location where a radio wave can be received from the antenna. When receiving a read command from the antenna, a mobile tag attached to the mobile object and the fixed tag send back a response signal at prescribed timing. A signal received from the fixed tag by the antenna is substantially constant. The signal from the fixed tag cannot be read while buried in a signal transmitted from the mobile tag to the antenna while the mobile tag is positioned at a location where communication with the antenna is expected. Conversely, when the mobile tag is at least a prescribed distance away from the antenna, the signal from the mobile tag cannot be read while buried in the signal from the fixed tag.
1. An RFID system, comprising:
a communication controller including a plurality of antennas provided in vicinities of each of a plurality of routes through which a mobile object, as an object of recognition, passes;
a plurality of fixed RFID tags arranged fixedly in vicinities each of the plurality of routes;
a mobile RFID tag having information related to the mobile object written therein and configured to move with the mobile object; and
a controller processor configured to control the communication controller, configured to obtain read information obtained by the communication controller through communication with the mobile RFID tag from the communication controller, and configured to recognize that the mobile object is positioned in a route of the plurality of routes corresponding to an antenna of the plurality of antennas that received a response signal of the mobile RFID tag including the read information when information from the response signal of the mobile RFID tag is obtained as read information;
wherein the mobile RFID tag and the plurality of fixed RFID tags respond at a prescribed timing to a received read command so that all of the mobile RFID tag and the plurality of fixed RFID tags which received the read command from one of the plurality of antennas respond in exact timing with each other;
wherein the plurality of fixed RFID tags respond to the read command received from one antenna of the plurality of antennas that is located in corresponding route with a signal having a level low enough to be buried in the response signal transmitted from the mobile RFID tag and the signal being unable to be decoded when the mobile RFID tag is located at location where communication with the one antenna is expected and a level high enough to bury a response signal transmitted from other of the mobile RFID tag and the plurality of fixed RFID tags which received the read command from the antenna and only a signal of the fixed RFID tag is decoded when the mobile RFID tag is not located at a location where communication with the antenna is expected;
wherein the mobile RFID tag responds to the read command received from the antenna located at the route through which the mobile RFID tag passes when the mobile RFID tag passes a location where communication with the antenna is expected with a signal having a level high enough to bury the response signal to the read command, the response signal transmitted from the fixed RFID tag located at the route, and only a signal of the mobile RFID tag is decoded; and
wherein the controller processor further includes an antenna controller that repeatedly executes a process while changing a control object to a subsequent antenna of the plurality of antennas depending on obtaining the read information of the response signal from the antenna transmitting the read command, the process including causing the antenna of each of the plurality of routes to transmit the read command in order, and receive the response signal to the read command from the mobile RFID tag and the fixed RFID tag;
a determiner that determines, when the read information of the response signal of the mobile RFID tag is obtained from the antenna of the predetermined route, whether or not the read information matches the route provided with the antenna that received the response signal including the read information; and
an outputter that outputs the result of the determination by the determiner.
2. The RFID system according to claim 1 , wherein
at least one of the mobile RFID tag and the plurality of fixed RFID tags are configured to change a reflection intensity of a radio wave for responding to a command from one of the plurality of antennas, in response to a command requesting the change of reflection intensity received from the one of the plurality of antennas.
3. The RFID system according to claim 1 , wherein
the mobile RFID tag responds to the read command received from the antenna located at the route through which the mobile RFID tag passes when the mobile RFID tag passes the location where communication with the antenna is expected with a signal having a level high enough to disable decoding a response signal transmitted from other mobile RFID tags positioned at out of the location where communication with the antenna is expected by burying the signal.