Distributed coupling antenna
An antenna including a ground plane region, a feed element having associated with it a first reactance and a coupling element having associated with it a second reactance, the second reactance being of opposite sign to the first reactance, the coupling element being coupled to the feed element and to the ground plane region and being located in close proximity to the ground plane region, wherein an impedance and hence a resonant frequency of the antenna depend on the first and second reactances.
1. An antenna comprising:
a ground plane region;
a feed element having associated with it a first reactance; and
a coupling element having associated with it a second reactance, said second reactance being of similar magnitude and opposite sign to said first reactance so as to cancel said first reactance, said coupling element being coupled to said feed element and to said ground plane region and being located in close proximity to said ground plane region,
wherein an impedance and hence a resonant frequency of the antenna depend on said first and second reactances.
2. An antenna according to claim 1 , wherein said feed element comprises an inductive feed element and said first reactance comprises an inductive reactance.
3. An antenna according to claim 2 , wherein said coupling element comprises a capacitive coupling element and said second reactance comprises a capacitive reactance.
4. An antenna according to claim 3 , wherein radio frequency electric fields are generated by said capacitive coupling element.
5. An antenna according to claim 4 , wherein said capacitive coupling element is coupled to said ground plane region by way of capacitive coupling of said radio frequency electric fields.
6. An antenna according to claim 5 , wherein said capacitive coupling is distributed over a significant portion of said ground plane region, such that currents are excited on said significant portion of said ground plane region.
7. An antenna according to claim 3 , wherein said inductive feed element and said capacitive coupling element have planar geometry.
8. An antenna according to claim 7 , wherein said inductive feed element and said capacitive coupling element are formed on a surface of a PCB.
9. An antenna according to claim 7 , wherein said inductive feed element comprises a planar spiral.
10. An antenna according to claim 7 , wherein said capacitive coupling element comprises a planar finger.
11. An antenna according to claim 3 , wherein said capacitive coupling element has three-dimensional geometry and is formed on a surface of a substrate other than a PCB.
12. An antenna according to claim 11 , wherein said substrate has high dielectric permittivity.
13. An antenna according to claim 11 , wherein said capacitive coupling element comprises interdigitated fingers separated by a non-conductive gap.
14. An antenna according to claim 1 , wherein said feed element comprises a capacitive feed element and said first reactance comprises a capacitive reactance.
15. An antenna according to claim 14 , wherein said coupling element comprises an inductive coupling element and said second reactance comprises an inductive reactance.
16. An antenna according to claim 15 , wherein radio frequency magnetic fields are generated by said inductive coupling element.
17. An antenna according to claim 16 , wherein said inductive coupling element is coupled to said ground plane region by way of inductive coupling of said radio frequency magnetic fields.
18. An antenna according to claim 17 , wherein said inductive coupling is distributed over a significant portion of said ground plane region, such that currents are excited on said significant portion of said ground plane region.
19. An antenna according to claim 15 , wherein said capacitive feed element and said inductive coupling element have planar geometry.
20. An antenna according to claim 19 , wherein said capacitive feed element and said inductive coupling element are formed on a surface of a PCB.
21. An antenna according to claim 19 , wherein said capacitive feed element comprises intermeshed capacitive combs.
22. An antenna according to claim 19 , wherein said inductive coupling element comprises a planar spiral.
23. An antenna according to claim 15 , wherein said inductive coupling element has three-dimensional geometry and is formed on a surface of a substrate other than a PCB.
24. An antenna according to claim 23 , wherein said inductive coupling element comprises at least two inductively coupled coils.
25. An antenna according to claim 1 , wherein said feed element is galvanically connected to a radio frequency input point by way of a feedline.
26. An antenna according to claim 25 , wherein said feedline includes circuit-matching components.
27. An antenna according to claim 1 , wherein said feed element is non-galvanically connected to a radio frequency input point.
28. An antenna according to claim 1 , wherein said coupling element is galvanically connected to said ground plane region.
29. An antenna according to claim 1 , also comprising a tuning mechanism.