Multimode antenna structure
A multimode antenna structure is provided for transmitting and receiving electromagnetic signals in a communications device. The communications device includes circuitry for processing signals communicated to and from the antenna structure. The antenna structure includes a plurality of antenna ports for coupling to the circuitry; a plurality of antenna elements, each operatively coupled to a different one of the antenna ports; and a plurality of connecting elements. The connecting elements each electrically connect neighboring antenna elements such that the antenna elements and the connecting elements are arranged about the periphery of the antenna structure and form a single radiating structure. Electrical currents on one antenna element flow to connected neighboring antenna elements and generally bypass the antenna ports coupled to the neighboring antenna elements such that an antenna mode excited by one antenna port is generally electrically isolated from a mode excited by another antenna port at a given desired signal frequency range, and the antenna structure generates diverse antenna patterns.
1. A multimode antenna structure for transmitting and receiving electromagnetic signals in a communications device, the communications device comprising circuitry for processing signals communicated to and from the multimode antenna structure, the multimode antenna structure comprising:
a plurality of antenna ports for coupling to the circuitry;
a plurality of antenna elements, each operatively coupled to a different one of the antenna ports; and
a plurality of coupling elements for electrically coupling to neighboring antenna elements of the plurality of antenna elements such that the plurality of antenna elements and the plurality of coupling elements are arranged about a periphery of the multimode antenna structure and form a single radiating structure, wherein electrical currents on one antenna element of the plurality of antenna elements flow to the neighboring antenna elements and substantially bypass the plurality of antenna ports coupled to the neighboring antenna elements such that an antenna mode excited by one of the plurality of antenna ports is substantially electrically isolated from a mode excited by another one of the plurality of antenna ports at a given desired signal frequency range without coupling a decoupling network to the plurality of antenna ports, and the multimode antenna structure generates diverse antenna patterns, wherein each antenna element of the plurality of antenna elements comprises two branches of different lengths to create resonance at two different frequencies.
2. The multimode antenna structure of claim 1 wherein the plurality of antenna elements comprises three antenna elements and the plurality of connecting elements comprises three connecting elements.
3. The multimode antenna structure of claim 1 wherein the plurality of antenna elements are balanced by a common counterpoise.
4. The multimode antenna structure of claim 3 wherein the common counterpoise comprises a hollow conductive cylinder.
5. The multimode antenna structure of claim 4 , wherein each of the plurality of antenna ports is coupled to a cable extending through the hollow conductive cylinder.
6. The multimode antenna structure of claim 5 further comprising a choke comprising the hollow conductive cylinder through which each of the cables pass.
7. The multimode antenna structure of claim 6 wherein each of the cables is a coaxial cable having a cable shield electrically coupled to the choke at a common point.
8. The multimode antenna structure of claim 1 wherein each of the plurality of coupling elements has a tortuous configuration to provide a given electrical length.
9. The multimode antenna structure of claim 1 wherein the multimode antenna structure is constructed from a flexible printed circuit.
10. The multimode antenna structure of claim 9 wherein the flexible printed circuit is wrapped onto a cylinder and packaged in a cylindrical plastic enclosure.
11. The multimode antenna structure of claim 1 further comprising an inductive trace coupled to each antenna element of the plurality of antenna elements at a location on the plurality of antenna elements spaced apart from a respective antenna port of the plurality of antenna ports.
12. The multimode antenna structure of claim 1 wherein the multimode antenna structure is formed from a sheet of metal comprising a plurality of coplanar tabs, each connected to a respective antenna element of the plurality of antenna elements, the plurality of coplanar tabs being configured to be secured to an edge of a printed circuit board assembly.
13. A multimode antenna structure for transmitting and receiving electromagnetic signals in a communications device, the communications device comprising circuitry for processing signals communicated to and from the multimode antenna structure, the multimode antenna structure comprising:
a plurality of antenna ports for coupling to the circuitry;
a plurality of antenna elements, each operatively coupled to a different one of the antenna ports, the plurality of antenna elements arranged around a periphery of the multimode antenna structure; and
a coupling element electrically coupling the plurality of antenna elements to a common point to form a single radiating structure, wherein electrical currents on one antenna element of the plurality of antenna elements flow to another antenna element of the plurality of antenna elements and substantially bypass an antenna port of the plurality of antenna ports coupled to the another antenna element such that an antenna mode excited by the antenna port of the plurality of antenna ports is substantially electrically isolated from a mode excited by another antenna port of the plurality of antenna ports at a given desired signal frequency range without coupling a decoupling network to the plurality of antenna ports, and the antenna structure generates diverse antenna patterns, wherein each antenna element of the plurality of antenna elements comprises two branches of different lengths to create resonance at two different frequencies.
14. The multimode antenna structure of claim 13 wherein the plurality of antenna elements comprises four antenna elements.
15. The multimode antenna structure of claim 13 wherein the plurality of antenna elements are balanced by a common counterpoise.
16. The multimode antenna structure of claim 15 wherein the common counterpoise comprises a hollow conductive cylinder.
17. The multimode antenna structure of claim 16 wherein each antenna port of the plurality of antenna ports is coupled to a cable extending through the hollow conductive cylinder.
18. The multimode antenna structure of claim 17 further comprising a choke comprising the hollow conductive cylinder through which each of the cables pass.
19. The multimode antenna structure of claim 18 wherein each of the cables comprises a coaxial cable having a cable shield electrically coupled to the choke at the common point.
20. The multimode antenna structure of claim 13 further comprising an inductive trace coupled to each antenna element of the plurality of antenna elements at a location on the plurality of antenna elements spaced apart from a respective antenna port of the plurality of antenna ports.
21. The multimode antenna structure of claim 13 wherein the multimode antenna structure is formed from a sheet of metal.
22. The multimode antenna structure of claim 13 wherein the plurality of antenna elements comprises a plurality of monopole antenna elements constructed from a flexible printed circuit.
23. The multimode antenna structure of claim 22 wherein the coupling element is soldered to the flexible printed circuit.
24. The multimode antenna structure of claim 13 wherein the coupling element has a spoke-like shape.
25. An antenna structure for transmitting and receiving electromagnetic signals in a communications device, the communications device comprising circuitry for processing signals communicated to and from the antenna structure, the antenna structure comprising:
a plurality of antenna ports for coupling to the circuitry;
a plurality of antenna elements, each operatively coupled to a different one of the plurality of antenna ports, each antenna element of the plurality of antenna elements comprising upper and lower planar sections that are substantially parallel and spaced apart and a side section coupling the upper and lower sections; and
one or more coupling elements, each electrically coupling to neighboring antenna elements of the plurality of antenna elements at one of the planar sections such that the plurality of antenna elements form a radiating structure, wherein electrical currents on one antenna element of the plurality of antenna elements flow to a neighboring antenna element of the plurality of antenna elements and substantially bypass one antenna port of the plurality of antenna ports coupled to the neighboring antenna element, wherein the electrical currents flowing through the one antenna element and the neighboring antenna element have a magnitude such that an antenna mode excited by the one antenna port is substantially electrically isolated from a mode excited by another antenna port of the plurality of antenna ports at a given desired signal frequency range without coupling a decoupling network to the plurality of antenna ports, and the antenna structure generates diverse antenna patterns, wherein each antenna element of the plurality of antenna elements comprises two branches of different lengths to create resonance at two different frequencies.
26. The antenna structure of claim 25 wherein each of the one or more coupling elements has a tortuous configuration to provide a given electrical length.
27. The antenna structure of claim 25 wherein each of the plurality of antenna elements has a tortuous configuration to provide a given electrical length.
28. The antenna structure of claim 25 wherein the antenna structure is constructed from a sheet of metal.
29. The antenna structure of claim 25 wherein the one or more coupling elements comprise two coupling elements electrically coupling to the neighboring antenna elements.
30. The antenna structure of claim 25 wherein the lower planar section of each antenna element of the plurality of antenna elements is coupled to a printed circuit board assembly.