Cavity-backed slot antenna with an active artificial magnetic conductor
A cavity-backed slot antenna whose cavity has an artificial magnetic conductor (AMC) disposed therein, the AMC being loaded with active reactive elements. The active reactive elements are preferably formed by Non-Foster Circuits (NFCs).
1. A cavity-backed slot antenna having a cavity therein, the cavity-backed slot antenna comprising an artificial magnetic conductor (AMC) disposed in said cavity-backed slot antenna, the AMC being formed by an array of metal patches displaced by a distance above a bottom of said cavity, the metal patches have edges confronting sidewalls of the cavity, said edges being electrically connected to said sidewalls, the AMC being loaded with active reactive elements.
2. The cavity-backed slot antenna of claim 1 where the metal patches are arrayed on two columns running along a length of the cavity, with a gap between the columns.
3. The cavity-backed slot antenna of claim 2 where the reactive elements are electrically connected in the gap between the columns of patches.
4. The cavity-backed slot antenna of claim 1 wherein said active reactive elements are Non-Foster Circuits.
5. The cavity-backed slot antenna of claim 1 wherein said active reactive elements are varactors.
6. The cavity-backed slot antenna of claim 1 wherein said reactive elements are negative-inductance non-Foster circuits.
7. The cavity-backed slot antenna of claim 5 with a variable voltage source connected to the varactors.
8. The cavity-backed slot antenna of claim 6 where the NFC's inductance is tunable with an applied voltage.
9. The cavity-backed slot antenna of claim 1 where the patches are arrayed in a single column centered along the length of the cavity.
10. The cavity-backed slot antenna of claim 8 where two reactive elements are electrically connected between each patch and either side of sidewalls of the cavity.
11. A cavity-backed slot antenna whose cavity has an artificial magnetic conductor (AMC) disposed therein, the AMC comprising an array of metal patches displaced by a set distance above a bottom of said cavity, the metal patches being arrayed in two columns running along a length of the cavity, and with a gap between the columns, the metal patches having edges confronting sidewalls of the cavity, said edges being electrically connected to said sidewalls, each gap between neighboring patches being bridged by reactive elements.
12. The cavity-backed slot antenna of claim 11 wherein the reactive elements comprise Non-Foster Circuits.
13. A cavity-backed slot antenna having a cavity therein, the cavity-backed slot antenna comprising an artificial magnetic conductor (AMC) disposed in said cavity-backed slot antenna, the AMC comprising an array of metal patches displaced by a set distance above a bottom of said cavity, the metal patches being arrayed in a single column running along a length of the cavity, and with a gap between the column and sidewalls of the cavity, the metal patches having edges confronting sidewalls of the cavity, said edges being electrically coupled to said sidewalls via reactive elements.
14. The cavity-backed slot antenna of claim 13 wherein the reactive elements comprise Non-Foster Circuits.
15. A method of lowering a resonant frequency of a cavity backed slot antenna comprising the steps of:
(i) disposing an array of electrically conductive patches in a cavity of said cavity backed slot antenna adjacent a slot of said cavity backed slot antenna, the array of electrically conductive patches forming an artificial magnetic conductor;
(ii) coupling capacitive elements between said plurality of electrically conductive patches and an electrically conductive wall defining at least two edges of said cavity.
16. A method of increasing the bandwidth around a resonant frequency of a cavity backed slot antenna comprising the steps of:
(i) disposing an array of electrically conductive patches in a cavity of said cavity backed slot antenna adjacent a slot of said cavity backed slot antenna, the array of electrically conductive patches forming an artificial magnetic conductor;
(ii) coupling capacitive elements between said plurality of electrically conductive patches and an electrically conductive wall defining at least two edges of said cavity, said capacitive elements each having a negative capacitance.
17. The method of claim 16 wherein said capacitive elements also have a negative resistance associated therewith so that both said negative capacitance and said negative resistance is imposed between said plurality of electrically conductive patches and an electrically conductive wall defining at least two edges of said cavity.