Polarization independent active artificial magnetic conductor

• US 9,379,448 B2
• Filed: 02/24/2014
• Issued: 06/28/2016
• Est. Priority Date: 04/07/2011
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Gregoire, Daniel J., White, Carson R.
• Primary Examiner(s): Nguyen, Khai M
• Application Number:
  US14/188,225
• Publication Number:
  US 20150244080A1
• Time in Patent Office: 855 Days
• Field of Search: 343/909, 343/846, 343/848, 343/913
• US Class Current: 1/1
• CPC Class Codes: H01Q 15/002 said selective devices being reconfigurable or tunable, e.g. using switches or diodes
• CPC Class Codes: H01Q 15/0066 said selective devices being reconfigurable, tunable or controllable, e.g. using switches
• CPC Class Codes: H01Q 15/008 said selective devices having Sievenpipers' mushroom elements
• CPC Class Codes: H01Q 15/14 Reflecting surfaces; Equivalent structures electromagnetic shields H01Q1/526
• CPC Class Codes: H01Q 15/141 Apparatus or processes specially adapted for manufacturing reflecting surfaces
• CPC Class Codes: H01Q 15/142 using insulating material for supporting the reflecting surface
• CPC Class Codes: H01Q 15/148 with means for varying the reflecting properties H01Q15/147 takes precedence
• CPC Class Codes: H05K 1/165 incorporating printed inductors
• CPC Class Codes: H05K 2203/162 Testing a finished product, e.g. heat cycle testing of solder joints
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

An active artificial magnetic conductor includes a ground plane and an array of unit cells coupled to the ground plane. Each unit cell includes a low impedance shunt coupled to the ground plane and an impedance element coupled to the low impedance shunt. A plurality of non Foster circuits are coupled in two different directions between impedance elements of adjacent neighboring unit cells in the array of unit cells.

Claims

1. An active artificial magnetic conductor comprising:

a ground plane;

an array of unit cells coupled to the ground plane, each unit cell comprising;

a low-impedance shunt coupled to the ground plane; and

an impedance element coupled to the low impedance shunt; and

a plurality of non-Foster circuits coupled in two different directions between impedance elements of adjacent neighboring unit cells in the array of unit cells;

wherein the low impedance shunts coupled to the ground plane in each unit cell have a low inductance; and

wherein an inductance of the low inductance of the low-impedance shunts is such that the mutual coupling between impedance elements is minimized thereby making the active artificial magnetic conductor stable.

2. The active artificial magnetic conductor of claim 1 wherein the low impedance shunt has a cross-shaped cross section.

3. The active artificial magnetic conductor of claim 1 wherein the low impedance shunt has a circular cross section.

4. The active artificial magnetic conductor of claim 1 wherein the impedance element is metallic.

5. The active artificial magnetic conductor of claim 1 wherein the impedance element is rectangular or square.

6. The active artificial magnetic conductor of claim 5 wherein each non-Foster circuit is coupled to a side of the impedance element.

7. The active artificial magnetic conductor of claim 1 wherein the non-Foster circuit has a negative inductance.

8. The active artificial magnetic conductor of claim 1 wherein:

the array of unit cells are arranged in horizontal and vertical directions; and

the two different directions are the horizontal and vertical directions.

9. The active artificial magnetic conductor of claim 1 wherein:

each low-impedance shunt has a cross-shaped cross section with a half-width r or a full width of 2r;

each of the cross shaped sections has a thickness d;

each unit cell is an square of size a by a;

each impedance element is a square of size b by b; and

each low-impedance shunt has a height oft from the ground plane;

wherein a is greater than b and 2r is less than b.

10. The active artificial magnetic conductor of claim 9 wherein:

the array of unit cell comprises a 5×

5 unit cell array;

a equals 75 mm;

b equals 65 mm;

r equals 18.75 mm;

d equals 3 mm;

t equals 25 mm; and

an inductance L_NFC of each non-Foster circuit ranges from varying from −

45 nH to −

36 nH;

wherein the active artificial magnetic conductor is stable from 1200 MHz to 500 MHz with a ±

90°

bandwidth ranging from 50% to 96%.

11. The active artificial magnetic conductor of claim 1 wherein at frequencies below a resonant frequency self and mutual inductances of unit cells of the array of unit cells are approximated by an admittance matrix

12. The active artificial magnetic conductor of claim 1 wherein the ground plane is metallic.

13. The active artificial magnetic conductor of claim 1 further comprising:

a dielectric substrate;

wherein the dielectric substrate is between the impedance elements and the ground plane.

14. The active artificial magnetic conductor of claim 1

wherein an inductance L_NFC of each non-Foster circuit is less than −

36 nH.

15. A method of making an active artificial magnetic conductor comprising:

forming an array of unit cells coupled to a ground plane, each unit cell comprising;

a low-impedance shunt coupled to the ground plane; and

an impedance element coupled to the low impedance shunt; and

coupling a plurality of non-Foster circuits in two different directions between impedance elements of adjacent neighboring unit cells in the array of unit cells;

wherein the low impedance shunts coupled to the ground plane in each unit cell have a low inductance; and

wherein an inductance of the low inductance of the low-impedance shunts is such that the mutual coupling between impedance elements is minimized thereby making the active artificial magnetic conductor stable.

16. The method of claim 15 wherein the low impedance shunt has a cross-shaped cross section.

17. The method of claim 15 wherein the low impedance shunt has a circular cross section.

18. The method of claim 15 wherein the impedance element is rectangular or square.

19. The method of claim 18 wherein each non-Foster circuit is coupled to a side of the impedance element.

20. The method of claim 15 wherein:

the array of unit cells are arranged in horizontal and vertical directions; and

the two different directions are the horizontal and vertical directions.

21. The method of claim 15 wherein at frequencies below a resonant frequency self and mutual inductances of unit cells of the array of unit cells are approximated by an admittance matrix

22. The method of claim 15 further comprising:

providing a dielectric substrate between the impedance elements and the ground plane.

23. The method of claim 15 wherein an inductance L_NFC of each non-Foster circuit is less than −

36 nH.