US3719909A

US3719909A - Inter-resonator coupling

Info

Publication number: US3719909A
Application number: US00149620A
Authority: US
Inventors: H Hanft
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-06-03
Filing date: 1971-06-03
Publication date: 1973-03-06
Anticipated expiration: 1990-03-06

Abstract

In a multi-pole filter the coupling between adjacent cavity resonators is varied in accordance with the distance between the back wall of each cavity and the interconnecting conductor. A section of the interconnecting conductor is so shaped and mounted to assume different spacings from the wall of the cavity according to its rotary position. Means may be provided for locking the connecting conductor in position to set the desired spacing.

Description

United States Patent 91 Hanft INTER-RESONATOR COUPLING [76] Inventor: Herbert Hanft, 1412 Ivanhoe Street,

Alexandria, Va. 22304 [22] Filed: June 3, 1971 21 Appl. No.: 149,620

[52] U.S. Cl ..333/73 C, 333/82 B [51] Int. Cl..-. ..H0lp 1/20, HOlp 7/04 [58] Field of Search ..333/73, 73 C, 24, 31, 82 B [56] References Cited UNITED STATES PATENTS 2,919,418 12/1959 Reis ..333/3l 3,159,803 12/1964 Czubiak 3,624,563 '11/1971 Burley ..333/24 1 March 6, 1973 2,851,666 9/1958 Kfich ..333/73 C Primary ExaminerPaul L. Gensler Attorney-F. l-l. Henson and E. P. Klipfel [5 7] ABSTRACT In a multi-pole filter the coupling between adjacent cavity resonators is varied in accordance with the distance between the back wall of each cavity and the interconnecting conductor. A section of the interconnecting conductor is so shaped and mounted to assume different spacings from the wall of the cavity according toits rotary position. Means may be provided for locking the connecting conductor in position to set the desired spacing.

7 Claims, 3 Drawing Figures INTER-RESONATOR COUPLING CROSS-REFERENCES TO RELATED APPLICATIONS The output coupling is in the output cavity resonator and connects the multi-pole filter to a combining network and hence to an antenna.

In copending patent application Ser. No. 838,999, filed July 3, 1969, now U.S. Pat. No. 3,624,563, by Henry E. Burley and William H. Martin, entitled A Fixed Input Coupling Combination For Narrow Band Tunable Filters Suitable For Multi-Coupler Applications, assigned to the present assignee, there is disclosed and claimed an input coupling wherein the inner conductor of the input cavity resonator is connected to a generator through a choke which is connected at one end to the generator and at the opposite end by a tap to the inner conductor of the cavity.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a multistage filter and more particularly relates to an adjustable inter-resonator coupling for RF power from one resonator to the other in a stepless manner over a specificrange.

2. Description of the Prior Art In prior art multi-stage filters the RF power is coupled from the first resonant cavity to the second resonant cavity by means of an inter-resonator conductor soldered to the respective center conductors of each resonator. The second resonator is coupled to the third resonator, which 'may be the output resonator, in the same way. When the inter-resonator conductor is SUMMARY OF THE INVENTION Briefly, the present invention permits the interresonator coupling in a multi-resonator filter to be ad justable in a stepless fashion. It has a conductor member so shaped and mounted to assume different spacings from the wall of the cavity according to its rotary position. The present invention permits setting of the filter in field operation and in addition permits simplified manufacture and assembly procedures.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be had to the preferred embodiment, exemplary of the invention, shown in the accompanying drawings, in which:

FIG. 1 shows an illustrative embodiment of the present invention;

FIG. 2 is a cross-sectional view of the present invention; and

FIG. 3 is an isometric illustration of the present invention in an output cavity resonator.

DETAILED DESCRIPTION OF THE INVENTION A three-pole multi-stage filter is illustrated in FIG. 1. The

resonant cavities

2, 4 and 6 are mounted adjacent each other with each including a center conductor 10 foreshortened by a variable capacitor 12. An interresonator coupling 14 connects the center conductor of each adjacent cavity resonator. The coupler 14 includes a section 16 which is rotatably mounted so that its outer surface will assume different separation distances from the wall of the cavity according to its rotary position. When the surface of the section 16 is closer to the back wall of its cavity, the coupling between adjacent cavity resonators will be smaller. Increased coupling is obtained by increasing the distance of the sectionv 16 from the wall of the cavity. Section 16 is illustrated to be circular in cross sectional shape although other cross-sectional shaped such as elliptical could also be used. 1

FIG. 2 illustrates the adjustable inter-resonator coupling in greater detail. The connecting conductor includes the conductor member 16 which is rotated in position about its off-center axis/A socket head cap screw 18 secures the conductor member 16. in its desired rotary position. An access hole 20 in the center conductor 10 allows access to the screw 18. The connecting conductor 22 extends between adjacent cavities and electrically connects adjacent center conductors.

The cross-sectional view in FIG. 2 shows that the area of contact between

members

22 and 16, and also 16 and 10 consists of the area between two concentric circles. That is, it is a much smaller area than the outer diameter of conductor 22. The pressure per unit area exerted by tightening the screw 18 is much greater for this configuration because of the small contact area. This type of joint is made between members that have been buffed, heavily silver plated, and buffed again. The R.F. joints made in this manner provide a molecular silver-to-silver contact, which has better R.F. conductivity than hard silver soldered joints. The same type of joint is used between the center conductor and g the cavity, and also between the center conductor and capacitorgoose neck.

From FIG. 3 it can be seen that as the conductor memberis rotated the distance between the back wall 24 of the cavity and the outer surface of the conductor member will vary in accordance with its rotary position. It may be adjusted over the required range by simply loosening the socket head cap screw 18 and rotating the conductor member 16, and then securing its position by tightening the screw 18. The electrical effect is essentially due to the change in distance between the inter-resonator conductor and the cavity wall. The response of the filter is in part determined by the amount of inter-resonator coupling between resonators.

Thus, it should be readily apparent that an interresonator coupling has been provided which is adjustable over a given range of coupling by a simple mechanical means. The inter-resonator coupling minimizes power loss because of its size and improves R.F. connection because of novel R.F. joints. A more accurate control of the response of the filter is obtainable due to the more precise adjustment of the inter-resonator coupling. A I

While the present invention has been described with a degree of particularity for the purposes of illustration, it is to be understood that all modifications, suggestions and alternations within the spirit and scope of the present invention are herein meant to be included.

I claim as my invention:

1. In a multi-stage filter including a plurality of cavity resonators, each with a center conductor and a back wall, wherein adjacent resonators have outer walls in contact one with another; a rotatable conductor electrically connecting the center conductors of adjacent cavity resonators through apertures in said outer walls and so shaped and mounted to assume different spacings from the back wall of each cavity according to its rotary position for adjusting inter-resonator coupling between said resonators.

2. The combination of claim 1 including means for locking said rotatable conductor in rotary position when the desired inter-resonator coupling is set.

3. An inter-resonator coupling, comprising in combination; a plurality of cavity resonators, each enclosed by outer walls and each including a center conductor; and a rotatably mounted conductor electrically connecting the center conductors of adjacent cavity resonators through said outer walls and so shaped and mounted to assume different spacing from a selected wall of each cavity according to its rotary position whereby the range of coupling required between cavity resonators is spanned.

4. In a multi-stage filter, the combination comprising; a plurality of cavity resonators, each enclosed by outer walls and each with a center conductor; a connecting conductor extending from the center conductor of one cavity to the center conductor of an adjacent cavity through apertures in said walls; a section of said connecting conductor so shaped and mounted to assume different spacings from a selected wall of the cavity according to its rotary position.

5. In a multi-stage filter, the combination comprising: a plurality-of cavity resonators disposed adjacent each other, each with a back wall and each with a center conductor; and a conductor member connecting center conductors of adjacent cavities and mounted on an off center axis so that its outer surface will assume different distances from the wall of acavity according to its rotary position.

6. The combination of claim 5 wherein said conductor member is circular in cross-section.

7. The combination of claim 5 wherein the cross-section of said conductor member is elliptical.

Claims

5. In a multi-stage filter, the combination comprising: a plurality of cavity resonators disposed adjacent each other, each with a back wall and each with a center conductor; and a conductor member connecting center conductors of adjacent cavities and mounted on an off center axis so that its outer surface will assume different distances from the wall of a cavity according to its rotary position.