Non-Foster Active Impedance Circuit for Electrically Small Antennas

• US 20150318607A1
• Filed: 07/07/2015
• Published: 11/05/2015
• Est. Priority Date: 06/12/2012
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Inventors: Rockway, John D., Arceo, Diana, Church, Justin A., Chieh, Jia-Chi Samuel, Xu, Lu, Ryu, Albert
• Granted Patent: US 9,960,484 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 5/35 using two or more simultaneously fed points
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H03H 11/00 Networks using active elements

Abstract

An antenna comprising: a driven element; an input feed coupled to the driven element wherein the input feed is configured to be connected to a receiver; a non-Foster circuit having a negative impedance, wherein the non-Foster circuit is configured to actively load the antenna at a location on the antenna other than at the input feed; and wherein the antenna may be contained within an imaginary sphere having a radius a, and wherein the product ka is less than 0.5, where k is a wave number.

Claims

1. An antenna comprising:

a driven element;

an input feed coupled to the driven element wherein the input feed is configured to be connected to a receiver;

a non-Foster circuit having a negative impedance, wherein the non-Foster circuit is configured to actively load the antenna at a location on the antenna other than at the input feed; and

wherein the antenna may be contained within an imaginary sphere having a radius a, and wherein the product ka is less than 0.5, where k is a wave number.

2. The antenna of claim 1, wherein the non-Foster circuit comprises a negative inductor in parallel with a negative capacitor.

3. The antenna of claim 1, wherein the non-Foster circuit loads the antenna at locations on the antenna.

4. The antenna of claim 1, wherein the non-Foster circuit actively loads the antenna to the extent that the antenna'"'"'s matching bandwidth exceeds a matching bandwidth of a passively loaded antenna.

5. The antenna of claim 2, wherein the negative inductor is set to a value of −

26 nH and the negative capacitor is set to a value of −

3.5 pF.

6. The antenna of claim 1, wherein the non-Foster circuit is a −

LC tank circuit.

7. The antenna of claim 6, wherein the −

LC tank circuit comprises an open-circuit, stable negative capacitor circuit stacked on a short-circuit stable negative inductance circuit.

8. The antenna of claim 1, wherein the non-Foster circuit employs a common-mode feedback (CMFB) network to provide a stable DC operating point.

9. The antenna of claim 1, wherein the non-Foster circuit is based on a cross-coupled transistor pair so as to generate an effective negative current flow through a load of the transistors.

10. The antenna of claim 1, wherein the non-Foster circuit comprises a negative capacitance circuit stacked on a negative inductance circuit that employs a common mode feedback (CMFB) circuit to stabilize direct current (DC) operating conditions.

11. A method for providing an electrically small antenna where ka<

0.5 with a bandwidth beyond a Bode-Fano limit, where the antenna may be contained within an imaginary sphere having a radius a, and where k is a wave number, comprising the following steps;

providing a driven element having an input feed; and

actively loading the antenna with a Non-Foster circuit at a location on the antenna that is not at the input feed.

12. The method of claim 11, wherein the non-Foster circuit is a parallel −

L −

C circuit.

13. The method of claim 11, wherein the antenna is actively loaded at locations.

14. The method of claim 11, wherein the non-Foster circuit actively loads the antenna to the extent that the antenna'"'"'s matching bandwidth exceeds a matching bandwidth of a passively loaded antenna.

15. The method of claim 12, wherein the −

L portion of the circuit has a value of −

26 nH and the −

C portion of the circuit has a value of −

3.5 pF.

16. The method of claim 11, wherein the non-Foster circuit is a −

LC tank circuit.

17. The method of claim 16, wherein the step of actively loading the antenna further comprises stacking an open circuit stable negative capacitor circuit with a short circuit stable negative inductance circuit.

18. The method of claim 11, wherein the actively loading the antenna step further comprises the step of generating an effective negative current flow through a load of a cross-coupled pair of transistors.

19. The method of claim 17, further comprising the step of stabilizing direct current (DC) operating conditions with a common mode feedback (CMFB) circuit.

20. The method of claim 12 further comprising the step of tuning the negative capacitance with a varactor at a load of a Linvill circuit and tuning the negative inductance with a negative inductance inverter.