Frequency filter and its manufacturing process

• US 20060125579A1
• Filed: 06/21/2005
• Published: 06/15/2006
• Est. Priority Date: 06/22/2004
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: Baleras, Francois, Blondy, Pierre
• Granted Patent: US 7,332,988 B2
• Time in Patent Office: Days
• US Class Current: 333/210
• CPC Class Codes: H01P 1/207 Hollow waveguide filters H01P1/212, H01P1/213, H01P1/215, H01P1/219 take precedence
• CPC Class Codes: H01P 11/007 Manufacturing frequency-selective devices resonators H01P11/008

Abstract

The invention relates to a frequency filter comprising a structure with, on one face, two extreme evanescent areas and at least one wave guide area between the evanescent areas, characterised in that the at least one wave guide area and the evanescent areas form a single closed cavity, the said single cavity being partitioned by at least two resonator elements that are embedded in the said single cavity at placement areas and that contribute to delimiting the said at least one wave guide area and the evanescent areas. The invention also relates to a process for manufacturing at least one such frequency filter, the said process comprising the following steps: manufacture of a structure comprising at least one cavity on one of its faces, called the back face, embedment of at least two resonator elements in the cavity at placement areas so as to delimit the at least one wave guide area and the evanescent areas.

Claims

1. Frequency filter comprising a structure with, on one face, two extreme evanescent areas (25) and at least one wave guide area (24) between the evanescent areas, characterised in that the at least one wave guide area (24) and the evanescent areas (25) form a single closed cavity (21), the said single cavity (21) being partitioned by at least two resonator elements (20, 60) that are embedded in the said single cavity (21) at placement areas and that contribute to delimiting the said at least one wave guide area (24) and the evanescent areas (25).

2. Frequency filter according to claim 1, characterised in that the single cavity (21) has at least one wall (22) and/or a bottom (23) that has at least one protuberant part (200) and at least one setback part (300), the said parts forming a relief that helps with embedding the resonator elements (20, 60) in the single cavity (21) at their placement area.

3. Frequency filter according to claim 1, characterised in that the structure is made from a material with low dielectric losses.

4. Frequency filter according to claim 1, characterised in that the resonator elements are made from a material with high permittivity and low dielectric losses.

5. Frequency filter according to the previous claim, characterised in that the resonator elements are made from silicon or ceramic.

6. Frequency filter according to claim 1, characterised in that at least two resonator elements are made from an identical material and have identical dimensions.

7. Frequency filter according to any one of the previous claims, characterised in that it comprises an electromagnetic shielding, the said shielding comprising:

a first metallisation layer (27, 43, 53) covering the bottom (23) and the walls (22) of the single cavity (21) and the face (80) of the structure containing the single cavity,

a second metallisation layer (31) closing the single cavity (21) and being in electrical contact with the first metallisation layer (27, 43, 53) and with the resonator elements.

8. Frequency filter according to the previous claim, characterised in that the second metallisation layer (31) is deposited on a host substrate (32, 61) with low dielectric losses.

9. Frequency filter according to claim 7, characterised in that the shielding comprises at least two openings called coupling windows.

10. Frequency filter according to the previous claim, characterised in that these openings are made at the resonator elements.

11. Process for manufacturing at least one frequency filter according to any one of claims 1 to 10, the said manufacturing process comprising the following steps:

manufacture of a structure comprising at least one cavity (21) on one of its faces, called the back face (80),

embedment of at least two resonator elements (20, 60) in the cavity (21) at placement areas so as to delimit the at least one wave guide area (24) and the evanescent areas (25).

14. Process for manufacturing a filter according to claim 11, in which the manufacture of the structure comprises the following steps:

supply of a first substrate (40),

etching of at least the cavity in the said first substrate (40).

15. Process for manufacturing a filter according to the previous claim, characterised in that the first substrate (40) is made from a material with low dielectric losses.

16. Process for manufacturing a filter according to the previous claim, characterised in that the first substrate (40) is made from a material chosen among silicon, quartz or any other similar material.

17. Process for manufacturing a filter according to any one of claims 14 to 16, characterised in that the etching is a plasma etching and is made according to the following steps:

deposition of a layer of photosensitive resin (41) on the back face (80) of the first substrate (40),

exposure of the photosensitive resin (41) through a mask and development of the said resin,

etching of the first substrate (40),

elimination of the photosensitive resin (41),

deposition of a layer of dielectric material (42) on the back face of the first substrate.

18. Process for manufacturing a filter according to the previous claim, characterised in that the mask used has a pattern to obtain a cavity (21) with at least one protuberant part (200) and at least one setback part (300) in at least one wall (22) and/or the bottom (23) of the cavity (21).

19. Process for manufacturing a filter according to claim 17, characterised in that the dielectric material (42) is polycrystalline silicon, silica, an organic dielectric or multilayers.

20. Process for manufacturing a filter according to claim 11, characterised in that it includes the manufacture of resonator elements (60) comprising the following steps:

supply of a second substrate (50),

separation of resonator elements (60) by cutting or by etching of the said second substrate (50).

21. Process for manufacturing a filter according to the previous claim, characterised in that it also comprises a step to adjust the height of the said second substrate (50) after the step to supply the second substrate.

22. Process for manufacturing a filter according to claim 20, characterised in that the second substrate (50) is made from a material chosen from among silicon, alumina, quartz or any other similar material.

23. Process for manufacturing a filter according to claim 20, characterised in that the manufacture of resonator elements also includes a step to deposit a layer of a dielectric material (52) on a face of the second substrate (50), two opposite faces of the second substrate or four opposite faces of the second substrate.

12. Process for manufacturing at least one frequency filter according to the previous claim, characterised in that it also comprises a metallisation step of the back face (80) of the structure, the walls (22) and the bottom (23) of the cavity before the embedment step of the resonator elements (20, 60), and a step to close the cavity (21) using a metallisation layer (31) after the said embedment step.

13. Process for manufacturing at least one frequency filter according to the previous claim, characterised in that the metallisation layer used to close the cavity comprises at least two openings.

24. Process for manufacturing a filter according to the previous step, characterised in that the manufacture of resonator elements also includes a step to deposit a metallisation layer (53) on the face(s) of the second substrate (50) comprising a layer of dielectric material (52).