| 摘要 |
PROBLEM TO BE SOLVED: To provide a transmission antenna device for reader-writer having characteristics capable of generating strong magnetic field at the area near a transmission antenna and rapidly reducing magnetic field intensity away from the antenna. SOLUTION: A basic coil 31 in which two circular small loop-shaped coils 41 and 42 different in radius area concentrically arranged and connected to each other while inverting a winding wire direction and another basic coil 32 composed of two circular small loop-shaped coils 43 and 44 different in the radius of the coils 41, 42 are arranged in layer so as to be made concentric in the projection view from the direction of passing magnetic flux. Thus, the strong magnetic field is generated in the area near the basic coil 31 and the magnetic field intensily is rapidly reduced away from the coil 31 since the magnetic flux is bent outward while being affected by the adjacent coil. |
