Hybrid radio frequency / inductive loop antenna

Patent metadata

Field	Value
Publication number	US-9520638-B2
Application number	US-201414290906-A
Country	US
Kind code	B2
Filing date	May 29, 2014
Priority date	Jan 15, 2013
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

Abstract

Biometric monitoring devices, including various technologies that may be implemented in such devices, are discussed herein. Additionally, techniques, systems, and apparatuses are discussed herein for providing a hybrid antenna including an RF radiator and an electrically coupled inductive loop. The hybrid antenna is capable of providing both RF and induction functionality, e.g., radio frequency transmission/reception capabilities for Bluetooth as well as near-field-communications (NFC) functionality via the inductive loop. The inductive loop may be in conductive contact with the RF radiator or may be inductively coupled with the RF radiator and not in conductive contact with the RF radiator. The inductive loop may act as a planar element of a planar inverted-F antenna (PIFA).

First claim

What is claimed is:

1. An apparatus comprising:
a ground plane;
a radio-frequency radiator;
a feed post conductively connected to the radio-frequency radiator;
a shorting post, wherein the shorting post is connected to the radio-frequency radiator; and
a near-field communications (NFC) tag including an NFC circuit and
a multi-turn inductive loop configured to couple electrically with the radio-frequency radiator, the multi-turn inductive loop either in conductive contact with the radio-frequency radiator or not in conductive contact with the radio-frequency radiator, the radio-frequency radiator at least partially overlapping the turns in the multi-turn inductive loop, wherein:
the multi-turn inductive loop is conductively connected with the NFC integrated circuit and configured to inductively couple with a near-field magnetic field to provide power to the NFC circuit,
the NFC circuit, when powered, is configured to broadcast information stored within the NFC circuit, and
the multi-turn inductive loop of the NFC tag, the radio-frequency radiator, the ground plane, and the feed post together form a planar inverted-F antenna configured to produce and receive electro-magnetic radio-frequency signals, wherein the multi-turn inductive loop of the NFC tag serves as a radiator extension to the radio-frequency radiator when producing and receiving the electro-magnetic radio-frequency signals.

2. The apparatus of claim 1 , wherein the turns of the multi-turn inductive loop of the NFC tag at least partially overlap the ground plane.

3. The apparatus of claim 1 , wherein the radio-frequency radiator at least partially overlaps less than 20% of the turns in the multi-turn inductive loop of the NFC tag.

4. The apparatus of claim 1 , wherein the turns in the multi-turn inductive loop of the NFC tag that the radio-frequency radiator at least partially overlaps are outermost turns of the multi-turn inductive loop of the NFC tag.

5. The apparatus of claim 1 , wherein the radio-frequency radiator follows a path that is substantially aligned with paths followed by the turns of the multi-turn inductive loop of the NFC tag with which the radio-frequency radiator at least partially overlaps.

6. The apparatus of claim 1 , wherein the turns in the multi-turn inductive loop of the NFC tag follow a path that defines a major surface that faces towards the radio-frequency radiator.

7. The apparatus of claim 1 , wherein the multi-turn inductive loop of the NFC tag is separated from the radio-frequency radiator by a first gap.

8. The apparatus of claim 7 , wherein the NFC tag includes an insulating layer that is interposed between the radio-frequency radiator and the multi-turn inductive loop in the first gap.

9. The apparatus of claim 7 , further comprising:
a first housing portion; and a second housing portion, wherein:
the radio-frequency radiator is supported by the first housing portion, the NFC tag is supported by the second housing portion, and
the first housing portion is mated to the second housing portion such that the NFC tag and the radio-frequency radiator are separated by the first gap.

10. The apparatus of claim 7 , further comprising:
a plastic carrier; and
a substrate with a printed circuit, wherein:
the radio-frequency radiator is supported by the plastic carrier,

the plastic carrier is supported by the substrate with the printed circuit, the substrate with the printed circuit acts as the ground plane, and the NFC tag is also supported by the plastic carrier.

11. The apparatus of claim 7 , further comprising:
a housing having a first surface and a second surface, wherein:
the first surface and the second surface are nominally on opposing sides of a portion of the housing and define the first gap,
the radio-frequency radiator is formed by a metallization layer deposited on the first surface,
the NFC tag is located on or adjacent to the second surface such that the second surface is interposed between the first surface and the NFC tag.

12. The apparatus of claim 7 , further comprising:
a housing having a first surface and a second surface, wherein:
the first surface and the second surface are nominally on opposing sides of a portion of the housing and define the first gap,
the radio-frequency radiator is formed by a metallization layer deposited on the second surface,
the NFC tag is located on or adjacent to the second surface such that the radio-frequency radiator is interposed between the second surface and the NFC tag.

13. The apparatus of claim 7 , wherein the ground plane is provided by a structure located on an opposite side of the first housing portion from the radio-frequency radiator.

14. The apparatus of claim 13 , wherein the structure is selected from the group consisting of: a printed circuit board, a flexible circuit board, a metal plate contained within the apparatus, and a metal plate at least partially providing an exterior surface of the apparatus.

15. The apparatus of claim 7 , wherein:
the radio-frequency radiator has a nominal width of between about 0.5 mm and 1.5 mm and an average length of between about 10 mm and 25 mm, and
the multi-turn inductive loop of the NFC tag has an average path length of about 500 mm to 600 mm.

16. The apparatus of claim 7 , wherein the radio-frequency radiator is substantially the shape of a rectangle having a length-to-width aspect ratio of at least 10:1.

17. The apparatus of claim 7 , wherein the radio-frequency radiator is L-shaped.

18. The apparatus of claim 7 , wherein the radio-frequency radiator is U-shaped or C-shaped.

19. The apparatus of claim 1 , wherein the multi-turn inductive loop is offset from the ground plane in a direction normal to the ground plane.

20. The apparatus of claim 1 , wherein the radio-frequency radiator is offset from the ground plane by a first distance.

21. The apparatus of claim 1 , wherein the ground plane is a non-planar surface.

22. The apparatus of claim 1 , wherein the radio-frequency radiator and the multi-turn inductive loop of the NFC tag are in electrically-conductive contact with one another.

23. The apparatus of claim 1 , wherein the radio-frequency radiator and the multi-turn inductive loop of the NFC tag are formed from the same electrically-conductive trace.

24. The apparatus of claim 1 , further comprising:
a shorting post conductively connecting the radio-frequency radiator to the ground plane, wherein:
the multi-turn inductive loop of the NFC tag, the radio-frequency radiator, the ground plane, the shorting post, and the feed post together form a planar inverted-F antenna (PIFA) configured to produce and receive electro-magnetic radio-frequency signals in a Bluetooth-compatible frequency band, wherein the multi-turn inductive loop of the NFC tag serves as a radiator extension to the radio-frequency radiator when producing and receiving the electro-magnetic radio-frequency signals in the Bluetooth-compatible frequency band.

25. The apparatus of claim 24 , wherein:
the radio-frequency radiator, the ground plane, and the multi-turn inductive loop of the NFC tag are formed from a common conductive trace.

26. The apparatus of claim 1 , further comprising:
a shorting post conductively connecting the radio-frequency radiator to the ground plane, wherein:
the multi-turn inductive loop of the NFC tag, the radio-frequency radiator, the ground plane, the shorting post, an

Assignees

• Fitbit Inc

Inventors

• Baringer William B
• Martinez Mark Manuel

Classifications

• A61B5/02433

  for infrared radiation · CPC title

• H01Q21/28 Primary

  Combinations of substantially independent non-interacting antenna units or systems {(multiple beam H01Q25/00)} · CPC title

• H01Q1/273

  Adaptation for carrying or wearing by persons or animals · CPC title

• A61B5/02416

  using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence) · CPC title

• A61B5/4812

  Detecting sleep stages or cycles · CPC title