Magnetic antenna, and RF tag and board mounted with the RF tag
The present invention relates to an RF tag comprising a magnetic antenna for transmitting and receiving information using an electromagnetic induction method, and an IC mounted to the magnetic antenna, wherein the magnetic antenna comprises a magnetic core and a plurality of coils formed on the magnetic core; the coils each have an inductance L 1 satisfying the specific relational formula, and are connected in parallel to each other in an electric circuit and disposed in series on the magnetic core; and a combined inductance L 0 of the magnetic antenna satisfies the specific relational formula. The RF tag of the present invention is used as a magnetic antenna for information communication using a magnetic field component which is capable of satisfying both reduction in size and improvement in communication sensitivity.
1. An RF tag comprising a magnetic antenna for transmitting and receiving information using an electromagnetic induction method, and an IC mounted to the magnetic antenna, which magnetic antenna comprises a magnetic core and a plurality of coils formed on the magnetic core, which coils each have an inductance L 1 satisfying the following relational formula (1) such that the inductances L 1 of the coils are identical to each other, and are connected in parallel to each other in an electric circuit and disposed in series on the same, common magnetic core,
a combined inductance L 0 of the magnetic antenna satisfying the following relational formula (2):
L 1 ≧1/(4π 2 ×(operating frequency) 2 ×(capacitance of IC +parasitic capacitance of antenna)) <Relational formula (1)>
wherein L 1 is an inductance per one coil;
L 0 ≦1/(4π 2 ×(operating frequency) 2 ×(capacitance of IC +parasitic capacitance of antenna)) <Relational formula (2)>
wherein L 0 is a combined inductance of the magnetic antenna.
2. An RF tag according to claim 1 , wherein the RF tag is coated with a resin.
3. An RF tag according to claim 1 , wherein L 1 is not less than 3 times L 0 .