Hybrid piezoelectric device / radio frequency antenna

Patent metadata

Field	Value
Publication number	US-9660324-B2
Application number	US-201514880706-A
Country	US
Kind code	B2
Filing date	Oct 12, 2015
Priority date	Mar 5, 2014
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

A hybrid antenna including a piezoelectric device and an RF radiator. The hybrid antenna is capable of providing both RF and piezoelectric device functionality, e.g., radio frequency transmission/reception capabilities for radio frequency devices as well as sound-producing and/or energy-scavenging functionality via the piezoelectric device. The piezoelectric device may be in conductive contact with the RF radiator or may not be in conductive contact with the RF radiator.

First claim

What is claimed is:

1. An apparatus comprising:
a ground plane;
a radio-frequency radiator, the radiator offset from the ground plane in a direction substantially normal to the ground plane by a first distance;
a feed post conductively connected to the radiator; and
a piezoelectric assembly offset from the ground plane in a direction substantially normal to the ground plane by a second distance, the piezoelectric assembly configured to couple inductively with the radiator and being separated from the radiator by at least a housing structure of the apparatus, wherein the piezoelectric assembly, the radiator, the ground plane, and the feed post together form an antenna configured to produce electro-magnetic radio-frequency signals and receive electro-magnetic radio-frequency signals.

2. The apparatus of claim 1 , wherein:
the piezoelectric assembly comprises a piezoelectric material, a first electrode, and a second electrode,
the piezoelectric material is positioned between the first electrode and the second electrode, and
the piezoelectric assembly is configured to produce a piezoelectric effect and configured to be powered through mutual inductive coupling with the radiator.

3. The apparatus of claim 2 , wherein the piezoelectric material includes one or more compounds selected from the group consisting of: gallium orthophosphate, langasite, barium titanate, lead titanate, lead zirconate titanate, lithium niobate, lithium tantalate, sodium tungstate, zinc oxide, Ba2NaNb5O5, Pb2KNb5O15, sodium potassium niobate, bismuth ferrite, sodium niobate, bismuth titanate, sodium bismuth titanate, and polyvinylidene fluoride.

4. The apparatus of claim 1 , further comprising a current-blocking component, wherein:
the current-blocking component is configured to at least substantially block radio-frequency current from reaching the piezoelectric assembly; and
the current-blocking component is in conductive contact with the feed post.

5. The apparatus of claim 1 , wherein the piezoelectric assembly at least partially overlaps the ground plane.

6. The apparatus of claim 1 , wherein the apparatus further comprises an insulating layer that is interposed between the radiator and the piezoelectric assembly.

7. The apparatus of claim 1 , further comprising:
a first housing portion; and
a second housing portion, wherein:
the radiator is supported by the first housing portion,
the piezoelectric assembly is supported by the second housing portion, and
the first housing portion is mated to the second housing portion.

8. 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 radiator.

9. The apparatus of claim 8 , 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.

10. The apparatus of claim 1 , further comprising:
a plastic carrier; and
a substrate with a printed circuit, wherein:
the 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 piezoelectric assembly is also supported by the plastic carrier.

11. The apparatus of claim 1 , wherein the housing structure has 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 structure,
the radiator is formed by a metallization layer deposited on the first surface, and
the piezoelectric assembly is located on or adjacent to the second surface such that the second surface is interposed between the first surface and the piezoelectric assembly.

12. The apparatus of claim 1 , wherein the housing structure proximate to the radiator is less than or equal to 2 mm, and wherein the first distance is between about 0.5 mm and 10 mm.

13. The apparatus of claim 1 , wherein the piezoelectric assembly is substantially circular or substantially rectangular in overall shape.

14. The apparatus of claim 13 , wherein the radiator is substantially circular in overall shape and:
the radiator has an average diameter of between 5 mm and 25 mm; and
the piezoelectric assembly has an average diameter of between 5 mm and 25 mm.

15. The apparatus of claim 1 , wherein the radiator is O-shaped, C-shaped, L-shaped, U-shaped, or rectangular-shaped.

16. The apparatus of claim 1 , wherein the radiator is configured to couple inductively and directly with the piezoelectric assembly.

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

18. The apparatus of claim 1 , further comprising:
a first housing portion of a wearable device; and
a second housing portion of the wearable device and mated to the first housing portion, wherein the radiator is supported in a recess between the first housing portion and the second housing portion, the recess being positioned outside a display cover of the wearable device.

19. The apparatus of claim 1 , further comprising a shorting post conductively connecting the radiator to the ground plane, wherein:
the piezoelectric assembly, the radiator, the ground plane, the shorting post, and the feed post form an antenna configured to produce and receive electric radio-frequency signals in a Bluetooth-compatible frequency band.

20. The apparatus of claim 1 , further comprising a shorting post conductively connecting the radiator to the ground plane, wherein:
the piezoelectric assembly, the radiator, the ground plane, the shorting post, and the feed post form an antenna configured to produce and receive electric radio-frequency signals in a GPS-compatible frequency band.

21. The apparatus of claim 1 , wherein the radiator is interposed between the piezoelectric assembly and the ground plane.

22. The apparatus of claim 1 , further comprising a first electrical conductor and a second electrical conductor, wherein the piezoelectric assembly comprises a piezoelectric material between a first electrode and a second electrode, the first electrical conductor connected to the first electrode and the second electrical conductor connected to the second electrode.

23. The apparatus of claim 1 , wherein the piezoelectric assembly is configured to produce a sound or range of sounds.

24. The apparatus of claim 1 , further comprising a battery, wherein the piezoelectric assembly is configured to scavenge energy by converting vibrations induced in the piezoelectric assembly into an electrical charge and output the electrical charge to the battery.

25. The apparatus of claim 1 , wherein the antenna is a planar inverted-F antenna (PIFA).

26. A method comprising:
a) providing a radio-frequency radiator, a ground plane, and a feed post, wherein the radiator is separated from the ground plane by a first distance, and wherein the feed post is conductively connected to the radiator;
b) mounting the radiator to a first surface of a first housing component;
c) providing a piezoelectric assembly; and
d) placing the piezoelectric assembly such that the piezoelectric assembly is offset from the ground plane in a direction substantially normal to the ground plane by a second distance, and is configured to couple inductively with the

Assignees

• Fitbit Inc

Inventors

• Baringer William B

Classifications

• A61B5/4812

  Detecting sleep stages or cycles · CPC title

• B06B1/0644

  using a single piezoelectric element (B06B1/0688 takes precedence) · CPC title

• H01L41/25

  Electricity · mapped topic

• A61B5/1123

  Discriminating type of movement, e.g. walking or running (A61B5/1116, A61B5/112 take precedence) · CPC title

• A61B5/02427

  Details of sensor · CPC title