Magnetic antenna, and RF tag and board mounted with the RF tag

Patent metadata

Field	Value
Publication number	US-10027017-B2
Application number	US-201715459236-A
Country	US
Kind code	B2
Filing date	Mar 15, 2017
Priority date	Jan 30, 2009
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

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 L1 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 L0 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.

First claim

The invention claimed is:

1. A magnetic antenna comprising a magnetic core and a plurality of coils formed on the magnetic core, wherein each of the plurality of the coils formed on the magnetic core has an inductance L 1 satisfying the following relational formula (1) and is connected in parallel to each other in an electric circuit and disposed in series on the magnetic core, and wherein a combined inductance L 0 of the magnetic antenna satisfies 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)×(capacitance of IC+parasitic capacitance of antenna))  <Relational formula (2)>

wherein L 0 is a combined inductance of the magnetic antenna.

2. A system comprising the magnetic antenna according to claim 1 and a resin that coats the magnetic antenna.

3. A system comprising the magnetic antenna according to claim 1 and a board, wherein the magnetic antenna is fixed to a surface of the board.

4. A communication system comprising the magnetic antenna according to claim 1 and an IC.

Assignees

• Toda Kogyo Corp

Inventors

• Koujima Jun
• Ohmae Satoshi
• Kimura Tetsuya
• Sato Yoshiro

Classifications

• H01Q1/2225 Primary

  used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal · CPC title

• H01Q7/00

  Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop · CPC title

• H05K1/165

  incorporating printed inductors · CPC title

• H01Q7/08

  Ferrite rod or like elongated core · CPC title

• H05K2203/162

  Testing a finished product, e.g. heat cycle testing of solder joints · CPC title