WO2001035485A1

WO2001035485A1 - Improvements in cavity filters

Info

Publication number: WO2001035485A1
Application number: PCT/US2000/042015
Authority: WO
Inventors: Bruce G. Malcolm; Timothy B. Reeves
Original assignee: Trilithic, Inc.
Priority date: 1999-11-12
Filing date: 2000-11-10
Publication date: 2001-05-17
Also published as: AU3079201A; EP1230710A1; CA2391332A1; JP2003514421A

Abstract

A cavity filter (8) includes a cavity (10) constituting an electrically conductive enclosure (12, 14, 16, 18, 20, 22), at least one resonator element (24-1,...24-n) constructed from a dielectric material, and a support (30) constructed from a relatively low loss dielectric support material for supporting the at least one resonator element (24-1,...24-n) in a desired orientation in the cavity (10). The support material has substantially higher thermal conductivity than the dielectric material.

Description

IMPROVEMENTS IN CAVITY FILTERS

Cross-Reference to Related Applications

This Patent Cooperation Treaty application claims the benefit of the filing date of, and incorporates by reference, U.S.S.N. 60/165,369, filed November 12, 1999.

Field of the Invention

This invention relates to cavity filters of the type used in high frequency communication systems. It is disclosed in the context of an application of cavity filters for a satellite communication system, but has utility in other applications as well.

Background of the Invention The use of dielectric "puck" resonators in cavity filters is well known.

Such devices are used in a variety of RF applications. The wireless RF bands from 700 MHZ through 3 GHz, which include avionics, cellular/PCS, satellite base stations, and industrial/scientific/medical (so-called ISM) frequency bands, are presented as illustrative applications for puck-type dielectric resonator filters, but are by no means the only applications for such devices.

A significant problem that is faced in the implementation of such devices is that a number of the applications for such devices require high power handling capabilities. The dielectric resonators themselves are typically on the order of a few centimeters or so in diameter and a few centimeters or so in thickness, and the materials from which they are made have relatively low dielectric loss and the thermal behavior of good insulators. Since these devices are typically employed in communication systems, they must be implemented in ways which minimize frequency drift about communication carrier frequencies, and so on. Thus, controlling the temperatures of such devices is of considerable concern and interest to system and component designers. Disclosure of the Invention

According to one aspect of the invention, a cavity filter includes a cavity constituting an electrically conductive enclosure, at least one resonator element constructed from a dielectric material, and a support constructed from a relatively low loss dielectric support material for supporting the at least one resonator element in a desired orientation in the cavity. The support material has substantially higher thermal conductivity than the dielectric material.

Illustratively according to this aspect of the invention, the cavity filter includes multiple cavities, each having at least one resonator element constructed from a dielectric material, a support constructed from a relatively low loss dielectric support material for supporting the at least one resonator element in a desired orientation in the cavity. The support material has substantially higher thermal conductivity than the dielectric material.

Further illustratively according to this aspect of the invention, the at least one resonator element in each cavity includes a passageway.

Additionally illustratively according to this aspect of the invention, the support in each cavity includes a passageway.

Illustratively according to this aspect of the invention, each enclosure includes at least one first passageway between an interior of the enclosure and the exterior of the enclosure.

Additionally illustratively according to this aspect of the invention, the support in each cavity includes a heat pipe.

Further illustratively according to this aspect of the invention, each enclosure includes at least one second passageway remote from the first passageway between its interior and its exterior.

Additionally illustratively according to this aspect of the invention, each cavity further includes a somewhat disk-shaped element constructed from a very low loss dielectric material having substantially higher thermal conductivity than the dielectric material from which the at least one resonator element is constructed. The somewhat disk-shaped element is in heat conducting contact with the at least one resonator element. Illustratively according to this aspect of the invention, each somewhat disk-shaped element is in heat conducting contact with at least one of its respective support and its respective enclosure.

Further illustratively according to this aspect of the invention, the at least one resonator element in each cavity is generally right circular cylindrical in shape. Each cavity further includes a generally right circular cylindrical enclosure for at least partially surrounding a respective at least one resonator element in heat conducting contact.

Additionally illustratively according to this aspect of the invention, each cavity further includes an element having somewhat the configuration of a hub with radially outwardly extending spokes constructed from a very low loss dielectric material having substantially higher thermal conductivity than the dielectric material from which the at least one resonator element is constructed. Each somewhat hub- and-spokes configured element is in heat conducting contact with a respective at least one resonator element.

Illustratively according to this aspect of the invention, each somewhat hub-and-spokes configured element is in heat conducting contact with at least one of its respective support and its respective enclosure.

Additionally illustratively according to this aspect of the invention, each enclosure includes means, such as, for example, a groove, for engaging the outer extent of at least one of the spokes.

Illustratively according to this aspect of the invention, the apparatus further includes a manifold for supplying a cooling fluid to each said cavity. The manifold is coupled to each said cavity through that respective cavity's respective first through hole. Further illustratively according to this aspect of the invention, the apparatus further includes a device for establishing a pressure differentia] between the first and second through holes.

Additionally illustratively according to this aspect of the invention, the apparatus includes a pressure sensor for sensing a pressure in the manifold.

Additionally illustratively according to this aspect of the invention, the apparatus includes a coolant fluid temperature control unit for treating the flow of cooling fluid prior to the introduction of the cooling fluid into the manifold.

Illustratively according to this aspect of the invention, a circuit is provided for the recovery and recirculation of the cooling fluid.

Further illustratively according to this aspect of the invention, the circuit includes the coolant fluid temperature control unit.

Illustratively according to this aspect of the invention, the apparatus further includes a thermostat for controlling the coolant fluid temperature control unit. According to another aspect of the invention, a method for controlling the temperature of a cavity filter including providing a first passageway into a cavity of the cavity filter, and introducing into the cavity a low dielectric loss, substantially non-polar fluid.

Further illustratively according to this aspect of the invention, the method includes providing a second passageway into the cavity, and removing the fluid through the second passageway.

Additionally illustratively according to this aspect of the invention, introducing the fluid into the cavity and removing the fluid from the cavity together include continuously recirculating the fluid. Illustratively according to this aspect of the invention, continuously recirculating the fluid includes passing the fluid through a fluid temperature control device.

Further illustratively according to this aspect of the invention, the method includes monitoring a temperature of the fluid and controlling the fluid temperature control device based upon the monitored temperature of the fluid. Illustratively according to the invention, the cooling fluid includes a low dielectric loss, substantially nonpolar gas or mixture of low dielectric loss, substantially nonpolar gases.

Additionally or alternatively illustratively according to the invention, the cooling fluid includes a low dielectric loss, substantially nonpolar liquid or mixture of low dielectric loss, substantially nonpolar liquids.

Brief Descriptions of the Drawings

The invention may best be understood by referring to the following detailed description and accompanying drawings which illustrate the invention. In the drawings:

Fig. 1 illustrates a partly diagrammatic, exploded perspective view of a resonator constructed according to the invention;

Fig. 2 illustrates a partly diagrammatic, fragmentary sectional view, taken generally along section lines 2-2, of the resonator illustrated in Fig. 1 ;

Fig. 3 illustrates a partly diagrammatic, fragmentary sectional view of an alternative construction to the construction illustrated in Fig. 2;

Fig. 4 illustrates a partly diagrammatic, fragmentary sectional view of a further enhancement to the construction illustrated in Fig. 2 or Fig. 3; Fig. 5 illustrates a partly diagrammatic, fragmentary sectional view of another alternative construction to the construction illustrated in Fig. 2;

Fig. 6 illustrates a partly diagrammatic, fragmentary sectional view of another alternative construction to the construction illustrated in Fig. 2; and,

Fig. 7 illustrates a partly diagrammatic, fragmentary sectional view of another alternative construction to the construction illustrated in Fig. 2.

Detailed Descriptions of Illustrative Embodiments

A resonator element is enclosed in a thermally relatively highly conductive, very low loss dielectric material. To aid in the control of the temperature of a cavity filter including the resonator, the enclosure may be augmented by other temperature controlling measures, such as refrigeration systems, cooling fluid circulation systems, and the like. In some embodiments, the cooling fluid is air. In others, more exotic coolants can be circulated through the cavities containing such resonators.

Referring now to Figs. 1-2, a cavity filter 8 includes one or more cavities 10, each configured as a generally rectangular prism having electrically conductive walls 12, 14, 16, 18, 20 and 22. While the illustrated cavities 10 are generally rectangular prism shaped, it should be understood that any appropriately shaped cavity(ies) may be used in the implementation of the invention. In addition to being electrically conductive, walls 12, 14, 16, 18, 20 and 22 are thermally conductive. Each resonator cavity 10 houses one or more dielectric resonator elements 24-1 , . . . 24-n, which illustratively are dielectric puck resonators of generally right circular cylindrical shape. Again, it should be understood that, while puck-type resonator elements 24-1, . . . 24-n are illustrated, any resonant structure(s) may be used in the implementation of the invention.

Resonator elements 24-1 , . . . 24-n have through holes 25-1 , . . . 25-n which illustratively are of generally right circular cylindrical shape extending through them from one, 26-1 , . . . 26-n, of their respective generally parallel surfaces to the other, 28-1 , . . . 28-n, of their respective generally parallel surfaces. A supporting post or pillar 30 extends from one, 12, of the walls of each cavity 10 toward the center thereof. Post 30 is constructed from a very low loss dielectric material and has a through hole 32. Wall 12 is also provided with a generally centrally located passageway 34. Illustratively, passageway 34 may be surrounded by, for example, a counterbore 36 for receiving an end of post 30 configured to be received in counterbore 36, for example, by threading the adjacent surfaces of both post 30 and counterbore 36, or by a suitable low dielectric loss adhesive. Counterbore 36 typically does not extend all the way through wall 12. Wall 12 is also provided with a number, two in the illustrated embodiment, of through holes 38 disposed outwardly from passageway 34.

The end of post 30 remote from wall 12 is configured to receive a stack containing a somewhat disk-shaped enclosure element 40, one or more dielectric resonator elements 24-1, . . . 24-n, one or more somewhat disk-shaped elements 42-1, . . . 42-(n-l), and a somewhat disk-shaped enclosure element 44. Element 40 is configured to seat on a step 46 provided around the perimeter of post 30 at a distance from its end remote from wall 12 substantially equal to the combined thickness of the resonator(s) 24-1, . . . 24-n, element(s) 42-1, . . . 42-(n-l), where such element(s) 42-1, . . . 42-(n-l) is (are) present, and enclosure elements 40 and 44. The outer perimeter 48 of enclosure element 40 provides a seat for a generally right circular cylindrical enclosure sleeve 50 which is configured to slide with little clearance over the perimetrally outer surfaces 52-1 , . . . 52-n, 54-1, . . . 54-(n-l), 56 of resonator(s) 24-1, . . . 24-n, element(s) 42-1, . . . 42-(n-l), where present, and enclosure element 44.

The adjacent surfaces of post 30, enclosure element 40, resonator(s) 24-1 , . . . 24-n, element(s) 42-1 , . . . 42-(n-l), and enclosure element 44 are as smooth and close in tolerance as they can be made by accepted manufacturing techniques for the materials involved, and the assembly requirements for the illustrated embodiment. Resonator(s) 24-1, . . . 24-n illustratively is (are) constructed from barium, zinc, tantalum oxide. Post 30, enclosure element 40, element(s) 42-1, . . . 42-(n-l), and enclosure element 44 illustratively are constructed from beryllia, aluminum nitride or boron nitride. Beryllia has a thermal conductivity which approximates that of aluminum and is about six-tenths that of copper. Aluminum nitride and boron nitride have somewhat lower thermal conductivities, but are somewhat easier to work with. Beryllia has a dielectric loss constant which approximates that of sapphire. Aluminum nitride's and boron nitride's dielectric loss constants are somewhat higher, but are satisfactory for this application. Machining beryllia to close tolerances is problematic. Consequently, low dielectric loss resins, such as Vary Flex two component epoxy, type HV, available from Sigma Plastronics, P. O. Box 649, Whitmore Lake, MI, 48189, may be used between the adjacent surfaces of resonator(s) 24-1, . . . 24-n and post 30, enclosure element 40, spacer(s) 42-1, . . . 42- (n-1), and enclosure element 44 to reduce discontinuities that might otherwise affect the performance of the cavity filter 8. When the cavity filter 8 is assembled in this way, the through holes 25-1, . . . 25-n, 32, 34 align to provide a passageway into cavity 10 through wall 12 for the introduction of a low dielectric loss, nonpolar cooling fluid, such as air or a liquid such as Fluorinert™ liquid FC-40 available from 3M Specialty Materials Lab, Performance Materials Division, 3M Center, 236-2B-01, St. Paul, MN, 55144-1000. The fluid is exhausted from the cavity 10 through holes 38. In this way, the fluid circulates through aligned through holes 32 and 34, through cavity 10 to remove heat from resonator(s) 24-1, . . . 24-n and post 30, enclosure element 40, element(s) 42-1, . . . 42-(n-l), and enclosure element 44, and outward through holes 38.

To promote the exposure of all cavities 10 in an array of such cavities to the same cooling capacity, thereby increasing the likelihood that the dielectric properties of all cavities will remain substantially uniform, a manifold 62 is provided adjacent cavities 10. The cooling fluid is supplied to the manifold 62 from, for example, a pump or blower 64 under the control of a manifold 62 pressure sensor 66. Sensor 66 increases the likelihood of uniform flow rates of the cooling fluid through the cavities 10 if the dimensions of the cavities 10 and through holes 25-1, . . . 25-n, 32, 34 and 60 are chosen to provide substantially uniform flow rates among the cavities 10. To increase the likelihood of a constant temperature of the cooling fluid, the other variable which will affect the cooling of the cavities, a coolant fluid heat exchanger/conditioning unit 68 treats the flow of cooling fluid prior to the introduction of the cooling fluid into the manifold 62. Conditioning unit 68 operates under the control of, for example, a thermostat 70. If the cooling fluid is air, the conditioning unit may be an air conditioner. Air flowing from cavities 10 through holes 60 can be exhausted to atmosphere, or recycled through the air conditioner 68, as dictated by the needs of a particular application. If a cooling fluid such as Fluorinert™ fluid is used, this material quite likely will have to be recycled, owing to cost, environmental concerns, and so on.

In another embodiment of the invention illustrated in Fig. 3, a cavity filter 108 includes cavities 1 10, each configured as a generally rectangular prism having electrically conductive walls 1 12, 1 14, 1 16, 118, 120 and 122. Again, while the illustrated cavities 1 10 are generally rectangular prism shaped, it should be understood that any appropriately shaped cavity may be used in the implementation of the invention. In addition to being electrically conductive, walls 112, 114, 116, 118, 120 and 122 are thermally conductive. Each resonator cavity 1 10 houses one or more dielectric resonator elements 124-1, . . . 124-n, which illustratively are dielectric puck resonators of generally right circular cylindrical shape. Again, it should be understood that, while puck-type resonator elements 124-1, . . . 124-n are illustrated, any resonant structure(s) may be used in the implementation of the invention. Resonator elements 124-1, . . . 124-n have through holes which illustratively are of generally right circular cylindrical shape extending through them from one to the other of their respective generally parallel surfaces for receiving a supporting post or pillar 130. Supporting post or pillar 130 extends from one, 112, of the walls of cavity 1 10 toward the center thereof. Post 130 is constructed from a very low loss dielectric material and has a through hole 132. Wall 1 12 is also provided with a generally centrally located through hole 134. Wall 1 12 is also provided with a number, illustratively two, of through holes 138 disposed outwardly from through hole 134. The end of post 130 remote from wall 1 12 is configured to receive a stack containing an enclosure element 140 having somewhat the configuration of a hub 141 with radially outwardly extending spokes 143, one or more dielectric resonator elements 124-1, . . . 124-n, one or more elements 142-1 , . . . 142-(n-l), each having somewhat the configuration of a hub 145-1 , . . . 145-(n-l) with radially outwardly extending spokes 147-1, . . . 147-(n-l ), and an enclosure element 144 having somewhat the configuration of a hub 149 with radially outwardly extending spokes 151. Element 140 is configured to seat on a step 146 provided around the perimeter of post 130 at a distance from its end remote from wall 1 12 substantially equal to the combined thickness of the resonator(s) 124-1 , . . . 124-n, element(s) 142- 1, . . . 142-(n-l ), where such element(s) is (are) present, and enclosure elements 140, 144. A number of generally right circular cylindrical enclosure sleeves 150-1, . . . 150-(n-l) are configured to slide with little clearance over the perimetrally outer surfaces 152-1 , . . . 152-n of resonator(s) 124-1, . . . 124-n. The adjacent surfaces of post 130, enclosure element 140, resonator(s) 124-1, . . . 124-n, element(s) 142-1, . . . 142-(n-l), and enclosure element 144 are as smooth and close in tolerance as they can be made by accepted manufacturing techniques for the materials involved, and the assembly requirements for the illustrated embodiment. The perimetrally outer extents of the spokes of spacer elements 142-1, . . . 142-(n-l) may be accommodated in grooves provided in the sidewalls 114, 1 16, 118, 120. Again, low dielectric loss resins can be used between the adjacent surfaces of elements 142-1, . . . 142-(n-l) and the walls of the grooves to enhance the performance of cavity filter 108. The spokes 143, 147-1, . . . 147-(n-l), 151 may be aligned in a plane perpendicular to the plane of Fig. 3, or they may not, as the performance requirements of a particular application dictate. Alignment of the spokes results in less restricted flow of coolant through cavity 110, and less turbulence in that flow. Other orientations may result in less restricted flow of coolant through cavity 110, but may also result in increased cooling of the contents of cavity 110.

Again, when the cavity filter 108 is assembled in this way, the through holes 125-1, . . . 125-n, 132, 134 align to provide a passageway into cavity 1 10 through wall 112 for the introduction of a cooling fluid such as air or a low loss, nonpolar liquid such as Fluorinert™ fluid. The fluid is exhausted from the cavity 110 through holes 138. In this way, the fluid circulates through aligned holes 125-1, . . . 125-n, 132 and 134, through cavity 1 10 to remove heat from resonator(s) 124-1 , . . . 124-n and post 130, enclosure element 140, element(s) 142-1 , . . . 142-(n-l), and enclosure element 144, and outward through holes 138. It will be appreciated that in this embodiment it may be necessary to have removable walls 1 12, 1 16, 120, for example, in order to assemble cavity filter 108.

As another alternative to, or in combination with the above discussed cooling scheme, the walls 12, 14, 16, 18, 20, 22 of cavity 10 and 1 12, 1 14, 1 16, 118, 120, 122 of cavity 110 can be provided with through holes 160 for the flow of a coolant. The coolant may be a less exotic coolant, such as water or any of the currently commercially available halogenated hydrocarbon refrigerants or non- halogenated refrigerants, or it may be something more exotic, such as, for example, liquid carbon dioxide, liquid nitrogen, or the like.

As another alternative to, or in combination with the above discussed cooling schemes, some one or more of the walls 12, 14, 16, 18, 20, 22 of cavity 10 and walls 112, 114, 116, 1 18, 120, 122 of cavity 1 10 may be constructed of a more thermally conductive material such as, for example, copper. Of course, such a more thermally conductive material may need to be passivated against the environment in which it is going to reside. For example, if copper is used and will be exposed to atmosphere, the copper may need to be coated with, for example, silver to prevent the formation of thermally non-conductive copper oxides.

As another alternative, or in combination with any one or more of the above cooling schemes, one or more Peltier effect devices may be provided on the outside of one or more of the walls 12, 14, 16, 18, 20, 22 of cavity 10 and 112, 114, 116, 118, 120, 122 of cavity 110. As another alternative for cooling, and with reference to Fig. 5, posts 30, 130 can be configured as heat pipes 162 which extend not only upward within cavities 10, 1 10, but also downward and out to the exteriors of cavities 10, 1 10. The exterior ends 164 of heat pipes 162 can be equipped with heat sinks 166 (illustrated diagrammatically) as necessary to meet the heat dissipation requirements of a particular application.

In another embodiment of the invention illustrated in Fig. 6, a cavity filter 208 includes cavities 210, each configured as a generally rectangular prism having electrically conductive walls 212, 214, 216, 218, 220 and 222. Again, while the illustrated cavities 210 are generally rectangular prism shaped, it should be understood that any appropriately shaped cavity may be used in the implementation of the invention. In addition to being electrically conductive, walls 212, 214, 216, 218, 220 and 222 are thermally conductive. Each resonator cavity 210 houses one or more dielectric resonator elements 224-1-1, 224-1-2; . . . 224-n-l, 224-n-2, which illustratively are dielectric puck resonators of generally right circular cylindrical shape. Again, it should be understood that, while puck-type resonator elements 224- 1-1, 224-1-2; . . . 224-n-l , 224-n-2 are illustrated, any resonant structure(s) may be used in the implementation of the invention. Resonator elements 224-1-1, 224-1 -2; . . . 224-n-l, 224-n-2 have through holes which illustratively are of generally right circular cylindrical shape extending through them from one to the other of their respective generally parallel surfaces. The through holes in the inner resonator elements 224-1-1 , . . . 224-n-l receive a supporting post or pillar 230. Supporting post or pillar 230 extends from one, 212, of the walls of cavity 210 toward the center thereof. Post 230 is constructed from a very low loss dielectric material and has a through hole 232. Wall 212 is also provided with a generally centrally located through hole 234. Wall 212 is also provided with a number, illustratively two, of through holes 238 disposed outwardly from through hole 234. The end of post 230 remote from wall 212 is configured to receive a stack containing an enclosure element 240. Element 240 is configured to seat on a step 246 provided around the perimeter of post 230 at a distance from its end remote from wall 212 substantially equal to the combined thickness of the resonator(s) 224-1, . . . 224-n, element(s) 242-1, . . . 242-(n-l), where such element(s) is (are) present, and enclosure elements 240, 244. A number of generally right circular cylindrical enclosure sleeves 250-1-1 , . . . 250-(n-l)-l are configured to slide with little clearance over the perimetrally outer surfaces 252-1-1, . . . 252-n-l of resonator(s) 224-1-1, . . . 224-n-l and inside the perimetrally inner surfaces 252-1-2, . . . 252-n-2 of resonator(s) 224-1-2, . . . 224-n-2. A generally right circular cylindrical enclosure sleeve 250 is configured to slide with little clearance over the perimetrally outer surfaces 252-1-2, . . . 252-n-2 of resonator(s) 224-1-2, . . . 224-n-2. The adjacent surfaces of post 230, enclosure element 240, resonator(s) 224-1-1, 224-1-2; . . . 224-n-l, 224-n-2, element(s) 242-1 , . . . 242-(n-l ), and enclosure element 244 are as smooth and close in tolerance as they can be made by accepted manufacturing techniques for the materials involved, and the assembly requirements for the illustrated embodiment. Again, low dielectric loss resins can be used between the adjacent surfaces of elements 230, 240, 224-1-1 , 224-1-2; . . . 224-n-l, 224-n-2, 242-1 , . . . 242-(n-l), and 244 to enhance the performance of cavity filter 208.

Again, when the cavity filter 208 is assembled in this way, the through holes 225-1, . . . 225-n, 232, 234 align to provide a passageway into cavity 210 through wall 212 for the introduction of a cooling fluid such as air or a low loss, nonpolar liquid such as Fluorinert™ fluid. The fluid is exhausted from the cavity 210 through holes 238. In this way, the fluid circulates through aligned holes 225-1, . . . 225-n, 232 and 234, through cavity 210 to remove heat from resonator(s) 224-1-1 , 224-1-2; . . . 224-n-l, 224-n-2, post 230, enclosure element 240, element(s) 242-1 , . . . 242-(n-l), and enclosure element 244, and outward through holes 238. Yet another embodiment of the invention is illustrated in Fig. 7. In the embodiment illustrated in Fig. 7, supporting post or pillar 230a is threaded for threadably engaging wall 212a and the inner circumferential surfaces of resonator elements 224a-l-l; . . . 224a-n-l . Post 230a is threaded at end 270 past the point of step 246a, for threaded engagement with the inner circumferential surfaces of enclosure element 240a and dielectric resonator elements 224a-l-l ; . . . 224a-n-l . Additionally, in this embodiment post 230a is threaded at its lower end 260 for threaded engagement with threads provided for this purpose in wall 212a of cavity 210. All elements are configured with close tolerances providing little clearance between the threads. Low dielectric loss resins can be used between the surfaces of the elements to enhance the performance of the cavity filter 208, as described above. Of course, other cooling schemes are possible with cavity filters of the type illustrated and described.

Claims

CLAIMS:

1. A cavity filter including a cavity constituting an electrically conductive enclosure, at least one resonator element constructed from a dielectric material, a support constructed from a relatively low loss dielectric support material for supporting the at least one resonator element in a desired orientation in the cavity, the support material having substantially higher thermal conductivity than the dielectric material.

2. The apparatus of claim 1 wherein the cavity filter includes multiple cavities, each having at least one resonator element constructed from a dielectric material, a support constructed from a relatively low loss dielectric support material for supporting the at least one resonator element in a desired orientation in the cavity, the support material having substantially higher thermal conductivity than the dielectric material.

3. The apparatus of any preceding claim wherein the at least one resonator element in each cavity includes a passageway.

4. The apparatus of any preceding claim wherein the support in each cavity includes a passageway.

5. The apparatus of any preceding claim wherein the support in each cavity includes a heat pipe.

6. The apparatus of any preceding claim wherein each enclosure includes at least one first passageway between an interior of the enclosure and the exterior of the enclosure.

7. The apparatus of claim 6 wherein each enclosure includes at least one second passageway remote from the first passageway between its interior and its exterior.

8. The apparatus of any preceding claim wherein each cavity further including a somewhat disk-shaped element constructed from a very low loss dielectric material having substantially higher thermal conductivity than the dielectric material from which the at least one resonator element is constructed, the somewhat disk-shaped element in heat conducting contact with the at least one resonator element.

9. The apparatus of claim 8 wherein each somewhat disk-shaped element is in heat conducting contact with at least one of a respective support and a respective enclosure.

10. The apparatus of any preceding claim wherein the at least one resonator element in each cavity is generally right circular cylindrical in shape, each cavity further including a generally right circular cylindrical sleeve for at least partially surrounding a respective at least one resonator element in heat conducting contact.

11. The apparatus of claim 1, 2, 3, 4, 5, 6 or 7 wherein each cavity further includes an element having somewhat the configuration of a hub with radially outwardly extending spokes constructed from a very low loss dielectric material having substantially higher thermal conductivity than the dielectric material from which the at least one resonator element is constructed, each somewhat hub-and- spokes configured element in heat conducting contact with a respective at least one resonator element.

12. The apparatus of claim 1 1 wherein each somewhat hub-and- spokes configured element is in heat conducting contact with at least one of its respective support and its respective enclosure.

13. The apparatus of claim 12 wherein the at least one resonator element in each cavity is generally right circular cylindrical in shape, each cavity further including a generally right circular cylindrical enclosure for at least partially surrounding a respective at least one resonator element in heat conducting contact.

14. The apparatus of claim 12 wherein each enclosure includes means for engaging the outer extent of at least one of the spokes.

15. The apparatus of any preceding claim further including a manifold for supplying a cooling fluid to each said cavity, the manifold coupled to each said cavity through that respective cavity's respective first passageway.

16. The apparatus of claim 15 further including a device for establishing a pressure differential between the first and second passageways.

17. The apparatus of claim 16 further including a pressure sensor for sensing a pressure in the manifold.

18. The apparatus of claim 15, 16 or 17 wherein the cooling fluid includes a low dielectric loss, substantially nonpolar gas or mixture of low dielectric loss, substantially nonpolar gases.

19. The apparatus of claim 15, 16 or 17 wherein the cooling fluid includes a low dielectric loss, substantially nonpolar liquid or mixture of low dielectric loss, substantially nonpolar liquids.

20. The apparatus of claim 15, 16, 17, 18 or 19 further including a coolant fluid temperature control unit for treating the flow of cooling fluid prior to the introduction of the cooling fluid into the manifold.

21. The apparatus of claim 20 including a circuit for the recovery and recirculation of the cooling fluid.

22. The apparatus of claim 21 wherein the circuit includes the coolant fluid temperature control device.

23. The apparatus of claim 20, 21 or 22 further including a thermostat for controlling the coolant fluid temperature control device.

24. The apparatus of claim 15, 16, 17, 18 or 1 including a circuit for the recovery and recirculation of the cooling fluid.

25. A method for controlling the temperature of a cavity filter including providing a first passageway into a cavity of the cavity filter, and introducing into the cavity a low dielectric loss, substantially non-polar fluid.

26. The method of claim 25 further including providing a second passageway into the cavity, and removing the fluid through the second passageway.

27. The method of claim 26 wherein introducing the fluid into the cavity and removing the fluid from the cavity together include continuously recirculating the fluid.

28. The method of claim 27 wherein continuously recirculating the fluid includes passing the fluid through a fluid temperature control device.

29. The method of claim 28 further including monitoring a temperature of the fluid and controlling the fluid temperature control device based upon the monitored temperature of the fluid.