Antenna having passive booster for near field communication

• US 9,787,368 B2
• Filed: 10/17/2016
• Issued: 10/10/2017
• Est. Priority Date: 11/06/2015
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Wu, Shun-Te
• Primary Examiner(s): SANDIFORD, DEVAN A
• Application Number:
  US15/294,791
• Publication Number:
  US 20170134072A1
• Time in Patent Office: 358 Days
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/43 Antennas
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

A near field communication (NFC) antenna includes a ferrite sheet, an antenna coil, and a passive booster. The antenna coil is formed on the ferrite sheet, and includes an inner sub-coil. The passive booster is formed on the ferrite sheet. A projection of the passive booster onto a plane does not overlap with a projection of an area enclosed by the inner sub-coil onto the plane. The projection of the passive booster onto the plane overlaps with a projection of the antenna coil and a projection of the ferrite sheet onto the plane.

Claims

1. An antenna for near field communication, comprising:

a ferrite sheet;

an antenna coil formed on the ferrite sheet comprising a first sub-coil and a plurality of second sub-coils, wherein the first sub-coil is a most inner sub-coil of the antenna coil; and

a passive booster formed on the ferrite sheet, wherein magnetic fields induced by a coil current on the antenna coil and a coil current on the passive booster direct toward a same direction;

wherein a projection of the passive booster onto a plane does not overlap with a projection of an area enclosed by the first sub-coil onto the plane;

wherein the projection of the passive booster onto the plane overlaps with a projection of an area occupied by the plurality of second sub-coils, and completely overlaps with a projection of the ferrite sheet onto the plane.

2. The antenna of claim 1, wherein the antenna coil comprises:

a third sub-coil enclosing the plurality of second sub-coils, wherein the third sub-coil is a most outer sub-coil of the antenna coil;

a first trace connected to the first sub-coil; and

a second trace connected to the third sub-coil;

wherein either the first trace or the second trace is connected a feed point, and either the second trace or the first trace is connected to a ground for single end radio-frequency (RF) network application;

wherein the first trace or the second trace is connected two feed points, respectively for differential RF network application.

3. The antenna of claim 2, wherein the passive booster comprises at least one conductive sheet, and each of the at least one conductive sheet comprises:

a first edge, wherein a projection of the first edge onto the plane is aligned with the projection of the inner sub-coil onto the plane or overlap the projection of antenna coil on to the plane; and

a plurality of second edges, wherein a plurality of projections of the plurality of second edges onto the plane is within the projection of the ferrite sheet onto the plane.

4. The antenna of claim 3, wherein the first trace or second trace is adjacent to one of the at least one conductive sheet, and a gap is between the first trace or second trace and one of the plurality of second edges.

5. The antenna of claim 3, wherein the antenna coil shape is at least one of a square shape, circle shape, elliptic shape, multiple shape, and rectangle shape with two feeds.

6. The antenna of claim 3, wherein an area of the total conductive sheets is greater than one third of an area of the antenna coil.

7. The antenna of claim 3, wherein a projection of one of the plurality of second edges onto the plane is aligned with a projection of the outer sub-coil onto the plane.

8. The antenna of claim 1, further comprising a dielectric material formed between the antenna coil and the passive booster to isolate the antenna coil and the passive booster.

9. The antenna of claim 1, wherein the antenna coil is formed between the ferrite sheet and the passive booster.

10. The antenna of claim 1, wherein the passive booster is formed between the ferrite sheet and the antenna coil.

11. The antenna of claim 1, wherein the shape of antenna coil is at least one of a square shape, circle shape, elliptic shape, multiple shape, and rectangle shape with two feeds.