Mode selective coupler for whispering-gallery dielectric resonator

1. A whispering gallery mode dielectric resonator, comprising:

a conductive enclosure comprising a top, a bottom and walls;

a dielectric element disposed in the enclosure and operative to support a desired resonant mode that is dependent on a shape and dimensions of the dielectric resonator; and

a mode selective coupling structure disposed over the enclosure and configured to selectively couple electromagnetic energy of the desired mode and configured not to substantially couple electromagnetic energy of a spurious mode supported in a region between the enclosure and the dielectric element, wherein the mode selective coupling structure comprises: a first coupling element aligned with a first anti node of the resonant mode: and a second coupling element aligned with a second anti-node of the resonant mdoe.

2. A whispering gallery mode dielectric resonator as claimed in claim 1 , wherein the selectively coupled electromagnetic energy comprises an evanescent field in a region between the dielectric element and the enclosure.

3. A whispering gallery mode dielectric resonator as claimed in claim 1 , wherein the desired resonant mode has a spatial symmetry with a plurality of first anti-nodes and a plurality of second anti-nodes, having a phase of approximately 180° relative to a phase of the first anti-nodes, and the structure comprises: a plurality of coupling elements with one coupling element selectively aligned over each of the anti-nodes.

4. A whispering gallery mode dielectric resonator as claimed in claim 3 , wherein each of the coupling elements aligned over the first anti-nodes are connected together and each of the coupling elements aligned over the second anti-nodes are coupled together.

5. A whispering gallery mode dielectric resonator as claimed in claim 3 , wherein each of the coupling elements comprises: a transmission line connected to a conductive loop disposed over the respective first anti-node or second anti-node and oriented so that a magnetic field of the desired mode induces a current in the loop.

6. A whispering gallery mode dielectric resonator as claimed in claim 5 , wherein each of the transmission lines connected to loops disposed over one of the first anti-nodes are connected electrically in parallel; and each of the transmission lines connected to loops disposed over one of the second anti-nodes are connected electrically in parallel.

7. A whispering gallery mode dielectric resonator as claimed in claim 1 , wherein the dielectric element is a ring dielectric element.

8. A whispering gallery mode dielectric resonator as claimed in claim 1 , wherein the enclosure is cylindrically shaped and the structure is disposed over the top.

9. A whispering gallery mode dielectric resonator as claimed in claim 1 , wherein the enclosure is cylindrically shaped and the structure is disposed over the bottom.

10. An electrical oscillator circuit, comprising:

a whispering gallery mode dielectric resonator, comprising:

a conductive enclosure comprising a top, a bottom and walls; a dielectric element disposed in the enclosure and operative to support a desired resonant mode that is dependent on a shape and dimensions of the dielectric resonator; and a structure disposed over the enclosure and configured to selectively couple electromagnetic energy of the desired mode and configured not to substantially couple electromagnetic energy of a spurious mode supported in a region between the enclosure and the dielectric element;

a bandpass filter operative to filter spurious modes from the whispering gallery mode dielectric resonator wherein the structure comprises: a first coupling element aligned with a first anti-node of the resonant mode: and a second coupling element aligned with a second anti-node of the resonant mode; and

an amplifier connected to the filter.

11. An electrical oscillator circuit as claimed in claim 10 , wherein the selectively coupled electromagnetic energy comprises and evanescent field away in a region between the dielectric element and the enclosure.

12. An electrical oscillator circuit as claimed in claim 10 , wherein the desired resonant mode has a spatial symmetry with a plurality of first anti-nodes and a plurality of second anti-nodes, having a phase of approximately 180° relative to a phase of the first anti-nodes, and the structure comprises: a plurality of coupling elements with one coupling element selectively aligned over each of the anti-nodes.

13. An electrical oscillator circuit as claimed in claim 12 , wherein each of the coupling elements aligned over the first anti-nodes are connected together and each of the coupling elements aligned over the second anti-nodes are coupled together.

14. An electrical oscillator circuit as claimed in claim 12 , wherein each of the coupling elements comprises: a transmission line connected to a conductive loop disposed over the respective first anti-node or second anti-node and oriented so that a magnetic field of the desired mode induces a current in the loop.

15. An electrical oscillator circuit as claimed in claim 14 , wherein each of the transmission lines connected to loops disposed over one of the first anti-nodes are connected electrically in parallel; and each of the transmission lines connected to loops disposed over one of the second anti-nodes are connected electrically in parallel.

16. An electrical oscillator circuit whispering gallery mode dielectric resonator as claimed in claim 10 , wherein the dielectric element is a ring dielectric element.

17. An electrical oscillator circuit as claimed in claim 10 , wherein the enclosure is cylindrically shaped and the structure is disposed over the top.

18. An electrical oscillator circuit as claimed in claim 10 , wherein the enclosure is cylindrically shaped and the structure is disposed over the bottom.