Multiple antenna assembly utilizing electro band gap isolation structures
A multiple antenna assembly with high isolation between the antennas is disclosed. The assembly includes a dielectric substrate with a ground plane and first and second antennas thereon. One or more metal-dielectric isolation structures are on the substrate at locations at which an electric current is present that has a current density greater than a predefined threshold. Each metal-dielectric isolation structure resonates at a given frequency that inhibits mutual signal coupling between the first and second antennas. Various configurations, such as concentric ring patterns, for the metal-dielectric isolation structures are disclosed. A device can be provided to dynamically tune the given frequency of the metal-dielectric isolation structures to correspond to radio frequency signals emitted by the first and second antennas.
1. An antenna assembly for a wireless communication device comprising:
a substrate of dielectric material and having a first surface and a second surface on opposite sides of the substrate;
a ground plane formed by a layer of electrically conductive material on the first surface;
a first radiating element disposed on the substrate;
a second radiating element disposed on the substrate and spaced apart from the first radiating element; and
at least one metal-dielectric isolation structure supported on the substrate between the first and second radiating elements at positions only at which an electric current is present that has a current density greater than a predefined threshold, wherein each metal-dielectric isolation structure resonates at a given frequency that inhibits mutual signal coupling between the first and second radiating elements.
2. The antenna assembly as recited in claim 1 wherein each at least one metal-dielectric isolation structure comprises a pattern of slots in the layer of electrically conductive material.
3. The antenna assembly as recited in claim 1 wherein each at least one metal-dielectric isolation structure comprises a pattern of metal on the second surface of the substrate.
4. The antenna assembly as recited in claim 1 wherein each at least one metal-dielectric isolation structure comprises a pair of concentric rings each having a gap.
5. The antenna assembly as recited in claim 4 wherein the gap of one ring is diametrically opposite to the gap of the other ring and is oriented 180° with respect to the gap of the other ring.
6. The antenna assembly as recited in claim 4 wherein the pair of concentric rings are either circular or rectilinear.
7. The antenna assembly as recited in claim 4 further comprising a switch for selectively creating an electrical path between the pair of concentric rings that alters the given frequency of the at least one metal-dielectric structure.
8. The antenna assembly as recited in claim 1 wherein each at least one metal-dielectric isolation structure comprises a rectilinear ring within which is an element shaped like a Jerusalem cross.
9. The antenna assembly as recited in claim 1 wherein the predefined threshold is half of a maximum current density occurring at any place between the first and second radiating element.
10. The antenna assembly as recited in claim 1 further comprising a device for dynamically varying the given frequency of the at least one metal-dielectric isolation structure.
11. The antenna assembly as recited in claim 10 , wherein the device for dynamically varying the given frequency of the at least one metal dielectric structure is a variable tuning circuit comprising a capacitor.
12. The antenna assembly as recited in claim 1 , wherein the at least one metal-dielectric structure comprises a switch.
13. The antenna assembly as recited in claim 1 further comprising a layer of liquid crystal polymer on the substrate adjacent to the at least one metal-dielectric isolation structure for dynamically varying the given frequency at which the at least one metal-dielectric isolation structure resonates.
14. The antenna assembly as recited in claim 1 wherein there are a plurality of metal-dielectric isolation structures; and further comprising a separate inductive-capacitive lumped element network between adjacent ones of the plurality of metal-dielectric isolation structures for dynamically varying the given frequency.
15. An antenna assembly for a wireless communication device comprising:
a substrate of dielectric material and having a first surface and a second surface on opposite sides of the substrate;
a ground plane formed by a layer of electrically conductive material on the first surface;
a first radiating element disposed on the substrate;
a second radiating element disposed on the substrate and spaced apart from the first radiating element; and
a plurality of metal-dielectric isolation structures forming a non-periodic array on the substrate, wherein each metal-dielectric isolation structure resonates at a given frequency that inhibits mutual signal coupling between the first and second radiating elements.
16. The antenna assembly as recited in claim 15 wherein each of the plurality of metal-dielectric isolation structures on the substrate are at a location where an electric current is present that has a current density greater than a predefined threshold.
17. The antenna assembly as recited in claim 16 wherein the predefined threshold is half of a maximum current density occurring at any place between the first and second radiating elements.
18. The antenna assembly as recited in claim 15 wherein each at least one metal-dielectric isolation structure comprises a pair of either circular or rectilinear concentric rings, each having a gap.
19. The antenna assembly as recited in claim 18 wherein the gap of one ring is diametrically opposite to the gap of the other ring and is oriented 180° with respect to the gap of the other ring.
20. The antenna assembly as recited in claim 18 further comprising a switch for selectively creating an electrical path between the pair of concentric rings that alters the given frequency of the at least one metal-dielectric structure.
21. The antenna assembly as recited in claim 15 wherein each at least one metal-dielectric isolation structure comprises a rectilinear ring within which is an element shaped like a Jerusalem cross.
22. The antenna assembly as recited in claim 15 further comprising a device for varying the given frequency of the at least one metal-dielectric isolation structure.
23. The antenna assembly as recited in claim 15 further comprising a layer of liquid crystal polymer on the substrate adjacent to the at least one metal-dielectric isolation structure for dynamically varying the given frequency at which the at least one metal-dielectric isolation structure resonates.
24. The antenna assembly as recited in claim 15 wherein there are a plurality of metal-dielectric isolation structures; and further comprising a separate inductive-capacitive lumped element network between adjacent ones of the plurality of metal-dielectric isolation structures for dynamically varying the given frequency.