Low cost, 2D, electronically-steerable, artificial-impedance-surface antenna

• US 9,466,887 B2
• Filed: 07/03/2013
• Issued: 10/11/2016
• Est. Priority Date: 11/03/2010
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Gregoire, Daniel J., Colburn, Joseph S.
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/934,553
• Publication Number:
  US 20150009070A1
• Time in Patent Office: 1,196 Days
• Field of Search: 342/372, 342/368
• US Class Current: 1/1
• CPC Class Codes: H01Q 15/0066 said selective devices being reconfigurable, tunable or controllable, e.g. using switches
• CPC Class Codes: H01Q 3/46 Active lenses or reflecting arrays

Abstract

A steerable artificial impedance surface antenna steerable in phi and theta angles including a dielectric substrate, a plurality of metallic strips on a first surface of the dielectric substrate, the metallic strips spaced apart across a length of the dielectric substrate and each metallic strip extending along a width of the dielectric substrate, and surface wave feeds spaced apart along the width of the dielectric substrate near an edge of the dielectric substrate, wherein the dielectric substrate is substantially in an X-Y plane defined by an X axis and a Y axis, wherein the phi angle is an angle in the X-Y plane relative to the X axis, and wherein the theta angle is an angle relative to a Z axis orthogonal to the X-Y plane.

Claims

1. An artificial impedance surface antenna having a primary gain lobe steerable in phi and theta angles comprising:

a dielectric substrate;

a plurality of metallic strips on a first surface of the dielectric substrate, the metallic strips spaced apart across a length of the dielectric substrate and each metallic strip extending along a width of the dielectric substrate;

surface wave feeds spaced apart along the width of the dielectric substrate near an edge of the dielectric substrate;

a first circuit coupled to the surface wave feeds for controlling relative phase differences between each surface wave feed, wherein the phi angle is controlled by the relative phase differences between each surface wave feed; and

a second circuit coupled to the plurality of metallic strips for controlling voltages on each of the metallic strips, wherein the theta angle is controlled by the voltages on the plurality of metallic strips;

wherein the dielectric substrate is substantially in an X-Y plane defined by an X axis and a Y axis;

wherein the phi angle is an angle in the X-Y plane relative to the X axis; and

wherein the theta angle is an angle relative to a Z axis orthogonal to the X-Y plane.

2. The artificial impedance surface antenna of claim 1 further comprising:

at least one tunable element coupled between each adjacent pair of metallic strips.

3. The artificial impedance surface antenna of claim 2 wherein:

the tunable element comprises a plurality of varactors coupled between each adjacent pair of metallic strips.

4. The artificial impedance surface antenna of claim 3 wherein:

each respective varactor coupled to a respective metallic strip has a same polarity of the respective varactor coupled to the respective metallic strip.

5. The artificial impedance surface antenna of claim 2 wherein:

the tunable element comprises an electrically variable material between adjacent metallic strips.

6. The artificial impedance surface antenna of claim 5 wherein:

the electrically variable material comprises a liquid crystal material or barium strontium titanate (BST).

7. The artificial impedance surface antenna of claim 5 wherein:

the dielectric substrate is an inert substrate; and

the electrically variable material is embedded within the inert substrate.

8. The artificial impedance surface antenna of claim 1 wherein:

the surface wave feeds are configured so that a relative phase difference between each surface wave feed determines the phi angle for a primary gain lobe of the electronically steered artificial impedance surface antenna (AISA).

9. The artificial impedance surface antenna of claim 8 further comprising:

a radio frequency (RF) feed network coupled to the surface wave feeds.

10. The artificial impedance surface antenna of claim 9 wherein the radio frequency (RF) feed network comprises:

a transmit/receive module;

a plurality of phase shifters, respective phase shifters coupled to the transmit/receive module and to a respective surface wave feed; and

a phase shift controller coupled to the phase shifters.

11. The artificial impedance surface antenna of claim 1 wherein:

alternating metallic strips of the plurality of metallic strips are coupled to a ground; and

each metallic strip not coupled to ground is coupled to a respective voltage from a voltage source;

wherein the surface wave impedance of the dielectric substrate is varied by changing the respective voltages.

12. The artificial impedance surface antenna of claim 1 wherein:

each metallic strip is coupled to a voltage source;

wherein the surface wave impedance of the dielectric substrate is varied by changing the respective voltages applied from the voltage source to each respective metallic strip.

13. The artificial impedance surface antenna of claim 1 further comprising:

a ground plane on a second surface of the dielectric substrate opposite the first surface of the dielectric substrate.

14. The artificial impedance surface antenna of claim 1 wherein:

the metallic strips have centers spaced apart by a fraction of a wavelength of a surface wave propagated across the dielectric substrate; and

wherein the fraction is less than or equal to 0.2.

15. The artificial impedance surface antenna of claim 14 wherein:

the tunable elements are varactors; and

a spacing between adjacent varactors coupled between two adjacent metallic strips is approximately the same as the spacing between centers of adjacent metallic strips.

16. The artificial impedance surface antenna of claim 1 wherein:

the artificial impedance surface antenna has a surface-wave impedance Z_sw, that is modulated or varied periodically by applying voltages to the metallic strips such that at distance (x) away from the surface wave feeds the surface wave impedance varies according to;

Z_sw=X+M cos(2π

x/p)

where X and M are a mean impedance and an amplitude of modulation respectively, and p is a modulation period; and

the theta angle is related to the surface wave impedance modulation by

θ

=sin<sup>−

1</sup>(n_sw−

λ

/p)

where λ

is a wavelength of a surface wave propagated across the dielectric substrate, and

n_sw=√

{square root over ((X/377)²+1)}

is a mean surface-wave index.

17. An artificial impedance surface antenna having a primary gain lobe steerable in phi and theta angles comprising:

a dielectric substrate;

a plurality of metallic strips on a first surface of the dielectric substrate, the metallic strips spaced apart across a length of the dielectric substrate, the metallic strips having equally spaced centers, the metallic strips periodically varying in width with a period of p, and each metallic strip extending along a width of the dielectric substrate;

a first circuit coupled to the surface wave feeds for controlling relative phase differences between each surface wave feed, wherein the phi angle is controlled by the relative phase differences between each surface wave feed; and

a second circuit coupled to the plurality of metallic strips for controlling voltages on each of the metallic strips, wherein the theta angle is controlled by the voltages on the plurality of metallic strips;

surface wave feeds spaced apart along a width of the dielectric substrate near an edge of the dielectric substrate;

wherein the dielectric substrate is substantially in an X-Y plane defined by an X axis and a Y axis;

wherein the phi angle is an angle in the X-Y plane relative to the X axis; and

wherein the theta angle is an angle relative to a Z axis orthogonal to the X-Y plane.

18. The artificial impedance surface antenna of claim 17 further comprising:

at least one tunable element coupled between each adjacent pair of metallic strips.

19. The artificial impedance surface antenna of claim 18 wherein:

the tunable element comprises a plurality of varactors coupled between each adjacent pair of metallic strips; and

each respective varactor coupled to a respective metallic strip has a same polarity of the respective varactor coupled to the respective metallic strip.

20. The artificial impedance surface antenna of claim 18 wherein:

the tunable element comprises an electrically variable material between adjacent metallic strips.

21. The artificial impedance surface antenna of claim 20 wherein:

the electrically variable material comprises a liquid crystal material or barium strontium titanate (BST).

22. The artificial impedance surface antenna of claim 20 wherein:

the dielectric substrate is an inert substrate; and

the electrically variable material is embedded within an inert substrate.

23. The artificial impedance surface antenna of claim 17 wherein:

the surface wave feeds are configured so that a relative phase difference between each surface wave feed determines the phi angle for a primary gain lobe of the electronically steered artificial impedance surface antenna (AISA).

24. The artificial impedance surface antenna of claim 17 further comprising:

a ground plane on a second surface of the dielectric substrate opposite the first surface of the dielectric substrate.

25. The artificial impedance surface antenna of claim 17 wherein:

alternating metallic strips of the plurality of metallic strips are coupled to a first terminal of a variable voltage source; and

each metallic strip not coupled to the first terminal is coupled to a second terminal of the variable voltage source;

wherein the surface wave impedance of the artificial impedance surface antenna is varied by changing a voltage between the first and second terminals of the variable voltage source.

26. The artificial impedance surface antenna of claim 17 further comprising:

a radio frequency (RF) feed network coupled to the surface wave feeds.