WO2016138918A1

WO2016138918A1 - A temperature compensated waveguide device

Info

Publication number: WO2016138918A1
Application number: PCT/EP2015/054241
Authority: WO
Inventors: Anatoli Deleniv; Piotr Kozakowski
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-03-02
Filing date: 2015-03-02
Publication date: 2016-09-09

Abstract

The present disclosure relates to a waveguide device (1a, 1b, 1a', 1a") comprising a first wall element (2a, 2b; 2a') that is comprised in an at least partial microwave energy, confinement (3). The waveguide device (1a, 1b) comprises an external housing (5, 5") that is attached to the first wall element (2a, 2b; 2a') and comprises an inner chamber (6). The external housing (5, 5") has a longitudinal extension (E) perpendicular to a main planar extension of the first wall element (2a, 2b; 2a'), and has a first temperature expansion coefficient (t₁) in the longitudinal extension (E). The waveguide device (1a, 1b, 1a', 1a") further comprises an actuator rod (7) that extends along the longitudinal extension (E) and comprises a first part (12) attached to the external housing (5, 5"), and a second part (13). The second part (13) is arranged to at least partly extend into said confinement (3) via a rod aperture (4) positioned between said confinement (3) and the inner chamber (6). The first part (12) has a second temperature expansion coefficient (t₂) that falls below the first temperature expansion coefficient (t₁).

Description

TITLE

A temperature compensated waveguide device TECHNICAL FIELD

The present disclosure relates to a waveguide device, and in particular to a temperature compensated waveguide device.

BACKGROUND

Filters, resonators and other precision microwave components made in the alloy invar have a temperature stable performance not achievable with other materials. This is due to an extremely low temperature expansion coefficient of invar that allows keeping dimensional stability of such microwave components as the temperature changes. As invar is rather expensive, heavy and difficult to machine, there is need for alternative less expensive solutions that use temperature compensation techniques. Therefore, a number of approaches that allow design of temperature stable microwave components without using invar exist.

For example, there are temperature compensation methods using dielectric materials with negative temperature coefficient of dielectric constants inserted into a microwave component. Other temperature compensation methods utilize a bimetal. However, a sufficient compensation of temperature drift without fine tuning is not possible due to material tolerances. Another temperature compensation method uses memory shaped alloys, but these are not able to provide a linear compensation over the temperature range in question, having a hysteresis.

Many other temperature compensation methods exist, but all have problems providing a desired functionality, mainly due to adjustment procedures and choice of suitable materials. There thus exists a need for a waveguide device with enhanced temperature compensation properties compared to prior art.

SUMMARY

The object of the present disclosure is to provide a waveguide device with enhanced temperature compensation properties compared to prior art.

This object is achieved by means of a waveguide device comprising a first wall element that is comprised in an at least partial confinement that is arranged to at least partly confine microwave energy. The waveguide device comprises an external housing that is attached to the first wall element and comprises an inner chamber. The external housing has a longitudinal extension perpendicular to a main planar extension of the first wall element and has a first temperature expansion coefficient in the longitudinal extension. The waveguide device further comprises an actuator rod that extends along the longitudinal extension and comprises a first part and a second part, where the first part is attached to the external housing. The second part is arranged to at least partly extend into said confinement via a rod aperture positioned between said confinement and the inner chamber. The first part has a second temperature expansion coefficient which has a magnitude that falls below the magnitude of the first temperature expansion coefficient.

According to an example, the first part and the second part are made in the same material.

According to another example, the first part and the second part together form the actuator rod homogeneously.

According to another example, the first part and the second part are made different materials. According to another example, the second part is made in the same material as the external housing,

According to another example, the waveguide device is in the form of a cavity resonator, the first wall element forming a first resonator wall element.

According to another example, the waveguide device is in the form of a waveguide filter device, the first wall element forming a waveguide wall element.

According to another example, the rod aperture is formed in an electrically conducting foil membrane diaphragm that is attached to an opening in the first wall element. According to another example, the actuator rod is arranged to extend into said confinement from the rod aperture a certain present protrusion distance that is dependent on the temperature due to the difference between the first temperature expansion coefficient and the second temperature expansion coefficient.

Other examples are evident from the dependent claims.

A number of advantages are obtained by means of the present disclosure, for example:

- No unusual, rare or expensive materials have to be used for any one of the parts of the actuator rod or the external housing.

- There is no need in fine tuning of the compensation.

- The waveguide device will have a very stable and reproducible temperature performance. - The length of the actuator can be scaled using the diameter of the second part that defines the sensitivity of the resonance frequency to change of intrusion length ΔΙ.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described more in detail with reference to the appended drawings, where:

Figure 1 shows a schematic perspective view of a resonator device according to a first example;

Figure 2 shows a schematic side view of the resonator device according to the first example;

Figure 3 shows a schematic first section view of the resonator device according to the first example;

Figure 4 shows a schematic second section view of the resonator device according to the first example;

Figure 5 shows a schematic perspective view of a resonator device according to a second example;

Figure 6 shows a schematic side view of the resonator device according to the second example;

Figure 7 shows a schematic first section view of the resonator device according to the second example; Figure 8 shows a schematic second section view of the resonator device according to the second example; Figure 9 shows a schematic cut-open view of an external housing for both examples;

Figure 10 shows a schematic perspective view of a resonator device with an elliptical shape; and

Figure 1 1 shows a schematic perspective view of a resonator device with an external housing having an elliptical shape. DETAILED DESCRIPTION

With reference to Figure 1 , Figure 2 Figure 3 and Figure 4 where Figure 1 shows a perspective view of a resonator device, Figure 2 shows a side view of the resonator device and Figure 3 and Figure 4 show section views of the resonator device, a first example will now be described. A resonator device 1 a comprises a first wall element 2a, a second wall element 14, opposing the first wall element 2a, a third wall element 15 and an opposing fourth wall element 16, and a fifth wall element 17 and an opposing sixth wall element 18. All these wall elements constitute a confinement 3a that in this example confines an inner space that is constituted by a resonator cavity 19. The wall elements 2a, 14, 15, 1 6, 17, 18 are for example made in an electrically conducting material such as for example aluminium or other suitable metal. Alternatively, the wall elements 2a, 14, 15, 1 6, 17, 18 may be made by one or more plastic parts that are coated with an electrically conducting material. In accordance with the present disclosure, the resonator device 1 a comprises an external housing 5 that is attached to the first wall element 2a. The external housing 5 comprises an inner chamber 6 and has a longitudinal extension E perpendicular to a main planar extension of the first wall element 2a. The external housing 5 furthermore has a first temperature expansion coefficient ti in the longitudinal extension E. Figure 9 is a cut-open view of the external housing 5, and Figure 9 is common both for this first example and a second example that will be described later, since the external housing 5 is of the same kind for both examples.

The resonator device 1 a comprises an actuator rod 7 that extends along the longitudinal extension E and comprises a first part 12 and a second part 13, where the first part 12 is attached to the external housing 5, and where the second part 13 is arranged to at least partly extend a certain initial protrusion length L into the confinement 3 and its resonator cavity 19 via a rod aperture 4 positioned between the confinement 3 and the inner chamber 6. The first part 12 has a second temperature expansion coefficient t₂ which has a magnitude that falls below the magnitude of the first temperature expansion coefficient t-i . The second part 13 is made in a material that affects the electric properties of the resonator device 1 a, and is generally constituted by a conductor loading. In Figure 3 and Figure 4, the actuator rod 7 is omitted for reasons of clarity.

Here, the first part 12 of the actuator rod 7 is press-fitted in a holding aperture 9 in the external housing 5, but it is also conceivable that the first part 12 of the actuator rod 7 is structurally attached the external housing 5 by other means, i.e. is a part of the external housing 5.

As the temperature rises from a first temperature value Ti to a second temperature value T₂ that exceeds the first temperature value Ti , a part of the actuator rod 7 is withdrawn from the resonator cavity 19. This is due to difference between the first temperature expansion coefficient ti and the second temperature expansion coefficient t₂. A temperature change ΔΤ is defined as the difference between the second temperature value T₂ and the first temperature value Ti, i.e. T₂ - Ti, and a corresponding change of protrusion length is defined as ΔΙ. This means that present protrusion length is defined as the sum of the initial protrusion length L and the change of protrusion length ΔΙ, where, when the change of protrusion length ΔΙ equals zero, the present protrusion length equals the protrusion length L.

The change of protrusion length ΔΙ may be defined as:

AI = LxATx(t₂- t₁) (1 )

From equation (1 ) above, it follows that since the first temperature expansion coefficient ti exceeds the second temperature expansion coefficient t₂, the change of protrusion length ΔΙ is negative when the temperature change ΔΤ is positive, i.e. when the temperature rises.

The second part 13 is made in a material that affects the electric properties of the resonator device 1 and the change of protrusion length ΔΙ is dependent on temperature. This means that the second part 13 protrudes into the resonator cavity 19 to an extent that varies with temperature, and by matching that varying protrusion to how the rest of the resonator device changes with temperature, for example by means of a properly chosen length of the external housing 5, a more or less complete temperature compensation of the resonator cavity 19 can be achieved

In other words, as the temperature grows, the resonator cavity 19 becomes larger and the resonance frequency drifts down in frequency. At the same time, the conductor loading in the form of the second part 13 is removed from the resonator cavity 19, which has an opposite effect on the resonance frequency. If both effects are carefully balanced, almost zero temperature drift of the resonance frequency is achieved

The external housing 5 is made in any suitable material having a higher temperature expansion coefficient than the first part 12 of the actuator rod 7. The external housing 5 may be made in the same material as the rest of the resonator device 1 a, for example in the same piece of material as the first wall element 2a. The external housing 5 may alternatively be press-fitted or screw-mounted to the second element wall 2a. The first part 12 of the actuator rod 7 may for example be made in titanium or invar. The larger the difference between the first temperature expansion coefficient ti and the second temperature expansion coefficient t₂, the smaller is the required length of the actuator rod 7 and hence the external housing 5. The second part 13 of the actuator rod 7 may for example be made in the same material used for the first part 12 of the actuator rod 7, enabling the actuator rod 7 to be made as a single part. Alternatively, the second part 13 of the actuator rod 7 may be made in the same material as the rest of the resonator device 1 a. The second part 13 of the actuator rod 7 is separated from the external housing 5 by means of an RF (Radio Frequency) membrane that generally is constituted by a rod aperture 4. The rod aperture 4 is for example formed in an electrically conducting foil membrane diaphragm 10 that is attached to an opening 1 1 in the first wall element 2a. The actuator rod 7 is suitably made such that only the second part 13 is permitted to enter the resonator cavity 19 via the rod aperture 4. The first part 12 and the second part 13 of the actuator rod 7 may have different section areas. With reference to Figure 5, Figure 6, Figure 7 and Figure 8, where Figure 5 shows a perspective view of a waveguide filter device, Figure shows a side view of the waveguide filter device, and Figure 7 and Figure 8 show section views of the waveguide filter device, a second example will now be described. A waveguide filter device 1 b comprises a first wall element 2b, a second wall element 20, opposing the first wall element 2b, a third wall element 21 and an opposing fourth wall element 22. All these wall elements 2b, 20, 21 , 22 constitute a confinement 3b that in this example partly confines a longitudinally extending inner space 24.

The waveguide filter device 1 b comprises an external housing 5 that is attached to the first wall element 2b, the external housing 5 being of the same kind as in the first example, and therefore having the same reference number as per the first example, the external housing 5 comprises an inner chamber 6 and has a longitudinal extension E perpendicular to a main planar extension of the first wall element 2a. The external housing 5 furthermore has a first temperature expansion coefficient ti in the longitudinal extension E.

The description for the first example with reference to Figure 9 is substantially the same for the second example, Figure 9 being applicable for both examples. The waveguide filter device 1 b thus comprises an actuator rod 7 that extends along the longitudinal extension E and comprises a first part 12 and a second part 13, where the first part 12 is attached to the external housing 5, and where the second part 13 is arranged to at least partly extend a certain initial protrusion length L into the confinement 3b and its inner space 24 via a rod aperture 4 positioned between the confinement 3 and the inner chamber 6. The first part 12 has a second temperature expansion coefficient t₂ which has a magnitude that falls below the magnitude of the first temperature expansion coefficient t-i. The second part 13 is made in a material that affects the electric properties of the resonator device 1 a, and is generally constituted by a conductor loading. In Figure 7 and Figure 8 the actuator rod 7 is omitted for reasons of clarity.

For the same reasons as described in the first example, as the temperature grows, the inner space 19 becomes larger and the filter frequency band drifts down in frequency. At the same time, the conductor loading in the form of the second part 13 is removed from the inner space 19, which has an opposite effect on the filter frequency band. If both effects are carefully balanced, almost zero temperature drift of the resonance frequency is achieved All materials and examples of materials mentioned for the first example are applicable for all examples described as well for other conceivable waveguide devices within the frame of the present disclosure.

The present disclosure is not limited to the examples discussed above, but may vary freely within the scope of the appended claims. For example, the waveguide cavity resonator may have other shapes where the present disclosure still is applicable, for example cylindrical or polygonal. In Figure 10 there is a cavity resonator 1 a' that comprises an elliptical, in this example cylindrical, wall element 8 that is connected to the first resonator wall element 2a'. The first wall element 8 may be a degenerate or non-degenerate elliptical wall element (8) that is connected to the first resonator wall element Correspondingly, the external housing has been shown to have a square cross-section, but have many other shapes, for example elliptical, as illustrated in Figure 1 1 , where an elliptical, in this example cylindrical, external housing 5" is attached to the first wall element 2a of a resonator device 1 a". Generally, the external housing may have any non-degenerate or degenerate elliptical, cuboidal, cylindrical or spherical shape.

Also, at least one of the first part 12 and the second part 13 of the actuator rod 7 does not have to be cylindrically shaped is indicated in the examples, but may have any suitable shape or shapes; for example rectangular or polygonal. Generally, the first part 1 2 and the second part 13 may have a non-degenerate or degenerate rectangular and/or elliptical cross-section

It is to be noted that the waveguide devices 1 a, 1 b, 1 a', 1 a" are shown in a simplified manner to enhance comprehension of the present disclosure. For example, connectors, filter components, dielectric inserts and irises are not shown. Such components are well-known, and should of course be regarded as present where applicable. Generally, the present disclosure relates to a waveguide device 1 a, 1 b, 1 a', 1 a" comprising a first wall element 2a, 2b; 2a' that is comprised in an at least partial confinement 3, said confinement 3 being arranged to at least partly confine microwave energy, wherein the waveguide device 1 a, 1 b comprises an external housing 5, 5" that is attached to the first wall element 2a, 2b; 2a' and comprises an inner chamber 6, where the external housing 5, 5" has a longitudinal extension E perpendicular to a main planar extension of the first wall element 2a, 2b; 2a', and has a first temperature expansion coefficient ti in the longitudinal extension E, where the waveguide device 1 a, 1 b, 1 a', 1 a" further comprises an actuator rod 7 that extends along the longitudinal extension E and comprises a first part 12 and a second part 13, where the first part 12 is attached to the external housing and where the second part 13 is arranged to at least partly extend into said confinement 3 via a rod aperture 4 positioned between said confinement 3 and the inner chamber 6, where the first part 12 has a second temperature expansion coefficient t₂ which has a magnitude that falls below the magnitude of the first temperature expansion coefficient t-i . According to an example, the first part 12 and the second part 13 are made in the same material.

According to an example, the first part 12 and the second part 13 together form the actuator rod 7 homogeneously.

According to an example, the first part 12 and the second part 13 are made in different materials.

According to an example, the second part 13 is made in the same material as the external housing 5, 5". According to an example, the first part 12 and the second part 13 have a non-degenerate or degenerate rectangular, polygonal and/or elliptical cross- section According to an example, the waveguide device 1 a is in the form of a cavity resonator 1 a, the first wall element forming a first resonator wall element 2a.

According to an example, the cavity resonator 1 a' comprises a degenerate or non-degenerate elliptical wall element 8 that is connected to the first resonator wall element 2a'.

According to an example, the waveguide device 1 b is in the form of a waveguide filter device 1 b, the first wall element 2b forming a waveguide wall element 2b.

According to an example, the first part 12 of the actuator rod 7 is press-fitted in a holding aperture 9 in the external housing 5.

According to an example, the first part 12 of the actuator rod 7 is structurally attached the external housing 5.

According to an example, the rod aperture 4 is formed in an electrically conducting foil membrane diaphragm 10 that is attached to an opening 1 1 in the first wall element 2a, 2b; 2a'.

According to an example, the actuator rod 7 is arranged to extend into said confinement 3 from the rod aperture 4 a certain present protrusion distance D ± ΔΙ that is dependent on the temperature due to the difference between the first temperature expansion coefficient ti and the second temperature expansion coefficient t₂. According to an example, the external housing 5" has any non-degenerate or degenerate elliptical, cuboidal, cylindrical or spherical shape.

Claims

1 . A waveguide device (1 a, 1 b, 1 a', 1 a") comprising a first wall element (2a, 2b; 2a') that is comprised in an at least partial confinement (3), said confinement (3) being arranged to at least partly confine microwave energy, wherein the waveguide device (1 a, 1 b) comprises an external housing (5, 5") that is attached to the first wall element (2a, 2b; 2a') and comprises an inner chamber (6), where the external housing (5, 5") has a longitudinal extension (E) perpendicular to a main planar extension of the first wall element (2a, 2b; 2a'), and has a first temperature expansion coefficient (t-i) in the longitudinal extension (E), where the waveguide device (1 a, 1 b, 1 a', 1 a") further comprises an actuator rod (7) that extends along the longitudinal extension (E) and comprises a first part (1 2) and a second part (1 3), where the first part (1 2) is attached to the external housing and where the second part (1 3) is arranged to at least partly extend into said confinement (3) via a rod aperture (4) positioned between said confinement (3) and the inner chamber (6), where the first part (1 2) has a second temperature expansion coefficient (t₂) which has a magnitude that falls below the magnitude of the first temperature expansion coefficient (t-i).

2. A waveguide device according to claim 1 , wherein the first part (1 2) and the second part (1 3) are made in the same material.

3. A waveguide device according to claim 2, wherein the first part (1 2) and the second part (13) together form the actuator rod (7) homogeneously.

4. A waveguide device according to claim 1 , wherein the first part (1 2) and the second part (1 3) are made in different materials.

5. A waveguide device according to claim 4, wherein the second part (13) is made in the same material as the external housing (5, 5").

6. A waveguide device according to any one of the previous claims, wherein the first part (12) and the second part (13) have a non-degenerate or degenerate rectangular, polygonal and/or elliptical cross-section

7. A waveguide device according to any one of the previous claims, wherein the waveguide device (1 a) is in the form of a cavity resonator (1 a), the first wall element forming a first resonator wall element (2a).

8. A waveguide device according to claim 7, wherein the cavity resonator (1 a') comprises a degenerate or non-degenerate elliptical wall element (8) that is connected to the first resonator wall element (2a').

9. A waveguide device according to any one of the claims 1 -5, wherein the waveguide device (1 b) is in the form of a waveguide filter device

(1 b), the first wall element (2b) forming a waveguide wall element (2b).

10. A waveguide device according to any one of the previous claims, wherein the first part (12) of the actuator rod (7) is press-fitted in a holding aperture (9) in the external housing (5).

1 1 . A waveguide device according to any one of the claims 1 -9, wherein the first part (12) of the actuator rod (7) is structurally attached the external housing (5).

12. A waveguide device according to any one of the previous claims, wherein the rod aperture (4) is formed in an electrically conducting foil membrane diaphragm (10) that is attached to an opening (1 1 ) in the first wall element (2a, 2b; 2a').

13. A waveguide device according to any one of the previous claims, wherein the actuator rod (7) is arranged to extend into said confinement (3) from the rod aperture (4) a certain present protrusion distance (D ± ΔΙ) that is dependent on the temperature due to the difference between the first temperature expansion coefficient (t-i) and the second temperature expansion coefficient (t₂).

14. A waveguide device according to any one of the previous claims, wherein the external housing (5") has any non-degenerate or degenerate elliptical, cuboidal, cylindrical or spherical shape.