Portable Electronic Device

• US 20070247387A1
• Filed: 06/27/2007
• Published: 10/25/2007
• Est. Priority Date: 03/13/2006
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Ito, Hiromitsu, Yosui, Kuniaki, Kobayashi, Eiichi, Kubo, Hiroyuki
• Granted Patent: US 7,710,341 B2
• Time in Patent Office: Days
• US Class Current: 343/787
• CPC Class Codes: H01Q 7/08 Ferrite rod or like elongated core

Abstract

A portable electronic device includes a circuit board and an antenna coil installed on the circuit board. The antenna coil includes a magnetic core and a coil wound at either side of an unwound portion. The winding direction of the coil is changed at either side of the unwound portion. When the length of the magnetic core is defined as X and the distance between two intersecting points at which a virtual line formed by projecting the central line of the magnetic core onto the circuit board intersects the outer periphery of the circuit board is defined as Y, the antenna coil satisfies Y≧X≧0.8Y.

Claims

1. A portable electronic device comprising:

a circuit board; and

an antenna coil provided on the circuit board, the antenna coil including;

a magnetic core, and

a coil wound around the magnetic core, the coil including a first coil portion, a second coil portion, and an unwound portion at an intermediate portion of the magnetic core in a longitudinal direction thereof,

wherein winding directions of the first coil portion and the second coil portion differ from each other, and

wherein a length X of the magnetic core and a distance Y between two points at which a virtual line formed by projecting a central line of the magnetic core in an axial direction thereof onto the circuit board intersects an outer periphery of the circuit board, satisfies Y≧

X≧

0.8Y.

2. The portable electronic device according to claim 1, wherein a distance D1 between points x1 and y1 is equal to a distance D2 between points x2 and y2, where two intersecting points at which the virtual line intersects end surfaces of the magnetic core are defined as x1 and x2, a first of the two intersecting points at which the virtual line intersects the outer periphery of the circuit board proximal to the point x1 is defined as y1, and a second of the two intersecting points at which the virtual line intersects the outer periphery of the circuit board proximal to the point x2 is defined as y2.

3. The portable electronic device according to claim 1, wherein the circuit board is rectangular, and the axial direction of the magnetic core corresponds to a lateral direction of the circuit board.

4. The portable electronic device according to claim 1, wherein an electrode is provided on at least one surface of the magnetic core at the unwound portion.

5. The portable electronic device according to claim 4, wherein the electrode has at least one slit.

6. The portable electronic device according to claim 1, wherein the magnetic core has a raised portion projecting in a thickness direction of the magnetic core at the unwound portion.

7. The portable electronic device according to claim 6, wherein a second coil is wound around an outer periphery of the raised portion.

8. The portable electronic device according to claim 1, wherein the magnetic core has at least one cut-off portion at the unwound portion.

9. The portable electronic device according to claim 8, wherein the cut-off portion is provided in a surface of the magnetic core facing the circuit board.

10. The portable electronic device according to claim 8, wherein the cut-off portion is formed on a side surface of the magnetic core perpendicular to the circuit board.

11. The portable electronic device according claim 1, wherein a number of turns of the first coil portion and a number of turns of the second coil portion differ from each other.

12. The portable electronic device according claim 1, wherein the antenna coil is positioned over the circuit board so as to be separated from the circuit board by a distance, and an electrode is formed on a surface of the magnetic core facing the circuit board.

13. A portable electronic device comprising:

a circuit board; and

an antenna coil provided on the circuit board, the antenna coil including;

a first magnetic core and a second magnetic core;

a first coil portion wound around the first magnetic core; and

a second coil portion wound around the second magnetic core,

wherein a winding direction of the first coil portion differs from a winding direction of the second coil portion,

wherein the first magnetic core and the second magnetic core are juxtaposed relative to each other such that an axis of the first coil portion and an axis of the second coil portion correspond to each other and so that a gap is provided between the first magnetic core and the second magnetic core, and

wherein a length X of the antenna coil in an axial direction and a distance Y between two intersecting points at which a virtual line formed by projecting a central line of the antenna coil in the axial direction onto the circuit board intersects an outer periphery of the circuit board, satisfies Y≧

X≧

0.8Y.

14. The portable electronic device according to claim 13, wherein a distance D1 between points x1 and y1 is equal to a distance D2 between points x2 and y2, where two intersecting points at which the virtual line intersects both end surfaces of the antenna coil in the axial direction are defined as x1 and x2, a first of the two intersecting points at which the virtual line intersects the outer periphery of the circuit board proximal to the point x1 is defined as y1, and a second of the two intersecting points at which the virtual line intersects the outer periphery of the circuit board proximal to the point x2 is defined as y2.

15. The portable electronic device according to claim 13, wherein the length X of the antenna coil in the axial direction and a distance B between the first magnetic core and the second magnetic core satisfy 0.6X≧

B≧

0.4×

.

16. The portable electronic device according to claim 13, wherein the circuit board is rectangular, and the axial direction of the antenna coil corresponds to a lateral direction of the circuit board.

17. The portable electronic device according to claim 13, wherein the antenna coil is positioned over the circuit board so as to be separated from the circuit board by a distance, and an electrode is formed on respective surfaces of the first magnetic core and the second magnetic core facing the circuit board.

18. The portable electronic device according to claim 13, wherein the first coil portion and the second coil portion are connected to each other by a conductor provided on the circuit board.

19. The portable electronic device according to claim 13, wherein the first coil portion and the second coil portion are connected to each other by a conductor provided on a flexible substrate.