| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the influence of magnetic flux of an exciting coil and to improve the signal-to-noise ratio as the time of reading tag information by composing a receiving coil of a couple of differentially connected coils and arranging them so that pieces of magnetic flux applied to the respective coils from the exciting coil become equal in the absolute value. SOLUTION: The couple of coils 3A and 3B which are connected differentially to constitute the receiving coil are formed to 1/2 as large as the area of the surface that the exciting oil 1 forms, and arranged at positions where magnetic fields from the exciting coil 1 become equal without making the surfaces overlap with each other in the surface of the exciting coil 1. A radio tag 21 attached to an article 30 moving on a conveyor 22 one receiving an exciting signal from the exciting coil 1 sends tag information stored in the memory through a tag coil at, for example, a transmit signal frequency 1/2 as high as the exciting signal frequency. Either of the coils 3A and 3B when approaching the radio tag 21 can receive the tag information without being disturbed by the exciting signal. |
