Balanced dual-band embedded antenna

• US 8,659,483 B2
• Filed: 02/29/2012
• Issued: 02/25/2014
• Est. Priority Date: 02/29/2012
• Status: Active Grant

• Current Assignee: Digi International Inc.
• Original Assignee: Digi International Inc.
• Inventors: Ridgeway, Robert Wayne
• Primary Examiner(s): LE, HOANGANH T
• Application Number:
  US13/408,858
• Publication Number:
  US 20130222188A1
• Time in Patent Office: 727 Days
• Field of Search: 343/700.MS, 343/795, 343/846, 343/848
• US Class Current: 343/700.MS
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

A planar antenna, such as included as a portion of a printed circuit board (PCB) assembly, can include a dielectric layer and a first conductive layer mechanically coupled to the dielectric layer. In an example, the first conductive layer can include a first arm having a shape defined by a first outer border comprising a first conic section and a first inner border comprising a second conic section, a feed line coupled to the first arm at a feedpoint location at or near a central axis of the first arm, and a second arm offset from the first arm along the central axis of the first arm, the second arm defined by a shape at least in part mirroring a shape of the first arm.

Claims

1. A planar antenna, comprising:

a dielectric layer; and

a first conductive layer mechanically coupled to the dielectric layer, the first conductive layer comprising;

a first arm having a shape defined by a first outer border comprising a first conic section and a first inner border comprising a second conic section;

a feed line coupled to the first arm at a feedpoint location at or near a central axis of the first arm; and

a second arm offset from the first arm along the central axis of the first arm, the second arm defined by a shape at least in part mirroring a shape of the first arm; and

wherein at least a portion of the feed line bifurcates the second arm into at least two portions;

wherein the at least two portions of the second arm are conductively coupled to a return conductor;

wherein the first and second arms comprise respective conductive strips including a lateral width that varies along the central axis;

wherein the respective conductive strips include a lateral width tapering from a wider width near the feedpoint location to a narrower width away from the feedpoint location; and

wherein the respective conductive strips include a lateral width that widens again at respective distal tips of the conductive strips away from the feedpoint location.

2. The planar antenna of claim 1, wherein the feed line is located laterally between respective return conductors comprising the at least two portions of the second arm.

3. The planar antenna of claim 2, wherein the feed line includes a first lateral width at a first location proximal to the first arm and a second lateral width at a second location distal to the first arm;

and

wherein the second location is in a region where the feed line is located laterally between the respective return conductors.

4. The planar antenna of claim 1, wherein one or more of a length of the first and second arms along the central axis, or a separation between respective distal tips of the conductive strips, is configured to provide at least two specified ranges of operating frequencies for wireless information transfer, the two specified ranges including respective center frequencies that are separated by at least an octave.

5. The planar antenna of claim 4, wherein a total length of the first and second arms is about 1.3 inches, wherein a first specified operating frequency range includes about 2.4 GHz, and wherein a second specified operating frequency range includes about 5.5 GHz.

6. The planar antenna of claim 1, comprising a second conductive layer mechanically coupled to the dielectric layer, the second conductive layer comprising:

a first conductor including a footprint substantially the same as the first arm and conductively coupled through one or more conductive vias through the dielectric layer to the first arm; and

a second conductor conductively isolated from the first conductor and including a footprint substantially the same as the second arm and conductively coupled through one or more conductive vias through the dielectric layer to the second arm.

7. The planar antenna of claim 6, wherein one or more of the second arm, the return conductor, or the feed line comprises a balun configured to provide balanced excitation of the first and second arms in response to the feed line being driven by an unbalanced source.

8. The planar antenna of claim 6, wherein one or more of a spatial arrangement, size, or shape of one or more of the second arm, the return conductor, or the feed line is configured to provide a specified input impedance.

9. A planar antenna, comprising:

a dielectric layer; and

a first conductive layer mechanically coupled to the dielectric layer, the first conductive layer comprising;

a first arm having a shape defined by a first outer border comprising a first conic section and a first inner border comprising a second conic section;

a feed line coupled to the first arm at a feedpoint location at or near a central axis of the first arm; and

a second arm offset from the first arm along the central axis of the first arm, the second arm defined by a shape at least in part mirroring a shape of the first arm; and

wherein at least a portion of the feed line bifurcates the second arm into at least two portions; and

wherein the at least two portions of the second arm are conductively coupled to a return conductor;

wherein the first and second arms comprise respective conductive strips including a lateral width that varies along the central axis;

wherein the respective conductive strips include a lateral width tapering from a wider width near the feedpoint location to a narrower width away from the feedpoint location; and

wherein the respective conductive strips include a lateral width that widens again at respective distal tips of the conductive strips away from the feedpoint location; and

a second conductive layer mechanically coupled to the dielectric layer, the second conductive layer comprising;

a first conductor including a footprint substantially the same as the first arm and conductively coupled through one or more conductive vias through the dielectric layer to the first arm; and

a second conductor conductively isolated from the first conductor and including a footprint substantially the same as the second arm and conductively coupled through one or more conductive vias through the dielectric layer to the second arm; and

wherein the feed line is located laterally between respective return conductors comprising the at least two portions of the second arm.

10. A method for providing a planar antenna, comprising

forming a dielectric layer;

and

forming a first conductive layer mechanically coupled to the dielectric layer, the forming the first conductive layer comprising;

forming a first arm having a shape defined by a first outer border comprising a first conic section and a first inner border comprising a second conic section;

forming a feed line coupled to the first arm at a feedpoint location at or near a central axis of the first arm; and

forming a second arm offset from the first arm along the central axis of the first arm, the second arm defined by a shape at least in part mirroring a shape of the first arm; and

forming a return conductor; and

wherein at least a portion of the feed line bifurcates the second arm into at least two portions; and

wherein the at least two portions of the second arm are conductively coupled to the return conductor;

wherein the first and second arms comprise respective conductive strips including a lateral width that varies along the central axis;

wherein the respective conductive strips include a lateral width tapering from a wider width near the feedpoint location to a narrower width away from the feedpoint location; and

wherein the respective conductive strips include a lateral width that widens again at respective distal tips of the conductive strips away from the feedpoint location.

11. The method of claim 10, wherein forming the feed line includes laterally locating the feed line between respective return conductors comprising the at least two portions of the second arm.

12. The method of claim 11, wherein the feed line includes a first lateral width at a first location proximal to the first arm and a second lateral width at a second location distal to the first arm;

and

wherein the second location is in a region where the feed line is located laterally between the respective return conductors.

13. The method of claim 10, wherein one or more of a total length of the first and second arms along the central axis, or a separation between respective distal tips of the conductive strips, is configured to provide at least two specified ranges of operating frequencies for wireless information transfer, the two specified ranges including respective center frequencies that are separated by at least an octave.

14. The method of claim 10, comprising forming a second conductive layer mechanically coupled to the dielectric layer, the forming the second conductive layer comprising:

forming a first conductor including a footprint substantially the same as the first arm and conductively coupled through one or more conductive vias through the dielectric layer to the first arm; and

forming a second conductor conductively isolated from the first conductor and including a footprint substantially the same as the second arm and conductively coupled through one or more conductive vias through the dielectric layer to the second arm.

15. The method of claim 14, wherein one or more of forming the second arm, forming the return conductor, or forming the feed line comprise forming a balun configured to provide balanced excitation of the first and second arms in response to the feed line being driven by an unbalanced source.

16. The method of claim 14, wherein one or more of forming the second arm, forming the return conductor, or forming the feed line comprises providing a specified input impedance using one or more of a spatial arrangement, size, or shape of one or more of the second arm, the return conductor, or the feed line.