US3373382A

US3373382A - Delay line with recessed support to prevent shorting by metal sputtering

Info

Publication number: US3373382A
Application number: US294633A
Authority: US
Inventors: Diamand Felix
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1962-08-23
Filing date: 1963-07-12
Publication date: 1968-03-12
Anticipated expiration: 1985-03-12
Also published as: FR1338984A; NL297019A; DE1227566B; GB1004955A

Description

F. DIAMAND March 12, 1968 DELAY LINE WITH REGESSED SUPPORT TO PREVE SHORTING BY METAL SPUTTERING Filed July 12, 1963 ndE INVENTOR: F/ix o/Amuvo BY I ATTORNEY;

United States Patent T DELAY LINE WITH RECESSED SUPPORT TO PREVENT HORTING BY METAL SPUTTERING Felix Diamand, Paris, France, assignor to CSF-(Jompagnie Generale de Telegraphic Sans Fil, Paris, France Filed July 12, 1963, Ser. No. 2%,633 Claims priority, application France, Aug. 23, 1962, 907,603, Patent 1,338,984 4 Claims. (Cl. 333-41) The present invention relates to delay lines utilized in hyperfrequency electron tubes, and more particularly to delay lines destined for very high frequencies and therefore having very small dimensions.

It is known that a high mechanical precision and indeformability are required of a delay line in order that the tube may correctly operate. These conditions are the more difficult to satisfy the higher the frequencies of operation and, consequently, the more the calculations of the delay line lead to smaller dimensions which diminish the mechanical rigidity and sturdiness.

It has already been proposed heretofore to resolve this difficulty by affixing the line to an insulating base, for example, by forming the same by photogravure on a plate. This structure, however, presents the inconvenience that as a result of unavoidable sputterings of the metal of the line, disintegrated or evaporated in part by the impact on the line of electrons of the beam, there is formed a conductive deposit on the relatively cold surface of the insulating base between the metallic elements of the line, producing at a more or less short interval a short-circuit harmful to the operation.

The object of the present invention is an improvement for the type of delay lines secured to an insulating base, and intended to remedy the aforementioned inconvenience.

According to the present invention, the insulating base has no longer the form of a plate as in the known structures but is cut in the manner to follow the form of the periodic elements of the line. A line of meander shape will therefore be secured to an insulating base also of meander shape or on a series of parallel insulating bars, an interdigital line on an insulating base in the form of interleaved combs, of a ladder or also on a series of parallel insulating bars, etc.

Accordingly, it is an object of the present invention to provide a delay line which effectively avoids, by simple means, and in a reliable manner the shortcomings noted hereinabove in connection with the prior art constructions.

It is another object of the present invention to provide a delay line of the type mentioned hereinabove, particularly a delay line for use at hyperfrequencies, which effectively avoids the danger of short-circuits as a result of sputtering of metal due to electron bombardment of the line.

Still a further object of the present invention resides in the provision of a very high frequency wave-guiding structure of the type mentioned hereinabove which is mechanically sturdy, may be readily machined and assembled yet assures proper operation for relatively long periods of time.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention and wherein:

FIGURE 1 is a partial longitudinal cross-sectional view of a prior art delay line, intended to explain the shortcomings, thereof;

3,373,382 Patented Mar. 12, 1968 FIGURE 2 is a partial longitudinal cross-sectional view, similar to FIGURE 1, of a delay line in accordance with the present invention;

FIGURE 3 is a partial horizontal cross-sectional view of a delay line that may be utilized in FIGURE 2, and

FIGURE 4 is a partial horizontal cross-sectional view, similar to FIGURE 3, and illustrating the insulating base adapted for use with the delay line of FIGURE '3.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, and more particularly to FIGURE 1 showing a cross-sectional view through a known delay line structure, reference numeral 1 designates therein a delay line which is fixed to an insulating base 2 in the form of a plate. The insulating base 2 itself is fixed to a metallic back-plate 3.

In this prior art structure, the sputterings of the metal of the line 1 fall on the relatively cold surface of the base 2 and form thereon a deposit 4 which short-circuits after a more or less short lapse of time the periodic elements of the delay line.

FIGURE 2 shows in cross section a delay line structure according to the present invention in which this inconvenience is avoided. In FIGURE 2, the delay line 1, for example, of copper and of meander shape, as is indicated by the horizontal cross-sectional view thereof in FIGURE 3, is no longer fixed on a plate 2 but on an insulating base 5, for example, of alumina, cut into meander shape like the line 1, the horizontal cross section of this insulating base 5 being shown in FIGURE 4. The insulating base 5 is secured on a metallic back-plate 3, for example, made of copper as in FIGURE 1. The manufacture of this assembly may comprise, for example, the preliminary and separate cutting of the line 1 and of the base 5, and the securing of one to the other by brazing. As an example of a modification, one could also simultaneously machine a metallic leaf or thin plate covering an insulating plate, the covering being made electrochemically, by pulverization or any other known manner.

As shown in FIGURE 2, the deposit 4, due to the metallic sputterings, occurs in this embodiment in the same manner as in FIGURE 1. However, in contradistinction to the embodiment of FIGURE 1, the deposit 4 of FIGURE 2 is formed directly on the metal of the back-plate 3 and is insulated from the metal of the delay line 1 by the thickness of the base 5. It is therefore no longer harmful as in the preceding case.

While I have shown and described one embodiment in accordance with the present invention, it is of course understood that the same is not limited thereto, but is susceptible of numerous changes and modifications as known to a person skilled in the art. For example, the present application is also applicable to any other form of known delay line with back-plate, interdigital line, ladder-type line, etc. The dimension d of the elements of the insulating base (FIGURE 4) need not be exactly equal to that of the elements of the delay line as shown in the drawing but may also be different therefrom, either larger or smaller. The portions A, B, C, and D of the meander of FIGURE 4 may also be suppressed whereby the meander is thus replaced by a series of parallel insulating bars. It is understood that all the delay lines comprising such modifications obvious to a person skilled in the art are equally within the spirit and scope of the present invention.

Thus, it is obvious that the present invention is not limited to the details shown and described herein but is susceptible of numerous modifications as pointed out above, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. In an evacuated tube electron discharge device having a delay line of geometrically periodical structure subject to metal sputtering, said delay line comprising an insulating base, a series of spaced metal elements fixed on said insulating base, and a conductive support for said base, said insulating base being provided with cut-out portions in the spaces between said elements sufficient to bare the surface of said conductive support within said spaces and cause the insulating base to conform substantially to the shape of the spaced metal elements.

2. In an evacuated tube electron discharge device having a delay line of geometrically periodical structure subject to lnetal sputtering, said delay line comprising an insulating base, a series of spaced metal rungs fixed to said insulating base, a conductive support for said base, said base having a shape conforming susbtantially to the shape of the spaced metal rungs including at least a series of insulating rungs each supporting a respective metal rung of said delay line, thereby leaving exposed parts of the surface of said conductive support in the spaces between said rungs.

3. In an evacuated tube electron discharge device having a delay line of geometrically periodical structure subject to metal sputtering, said delay line comprising an insulating base, a series of spaced metal rungs fixed to said insulating base, a conductive support for said base, said base having a shape including at least a series of in- 4 sulating rungs each supporting a respective metal rung of said delay line, thereby leaving exposed parts of the surface of said conductive support in the spaces between said rungs, and the width of said metal rungs substantially coinciding with the width of said insulating rungs.

4. In an evacuated tube electron discharge device, a wave-guiding structure having a plurality of geometrically periodical elements secured to an insulating base which in turn is fixed to a conductive support,

the improvement essentially consisting of conforming the insulating base substantially to the shape of the delay elements at least in part to thereby leave exposed parts of the surface of the conductive support in the spaces between the delay elements and avoid short circuits as a result of metallic deposits caused by sputtering of the metal from the delay elements.

References Cited UNITED STATES PATENTS 2,704,829 3/1955 Clay 333*31 3,173,111 3/1965 Kallmann 333-31 3,257,629 6/1966 Kornreich 333-31 FOREIGN PATENTS 767,077 1/ 1957 Great Britain. 708,601 5/1954 Great Britain.

ELI LIEBERMAN, Primary Examiner.

Claims

1. IN AN EVACUATED TUBE ELECTRON DISCHARGE DEVICE HAVING A DELAY LINE OF GEOMETRICALLY PERIODICAL STRUCTURE SUBJECT TO METAL SPUTTERING, SAID DELAY LINE COMPRISING AN INSULATING BASE, A SERIES OF SPACED METAL ELEMENTS FIXED ON SAID INSULATING BASE, AND A CONDUCTIVE SUPPORT FOR SAID BASE, SAID INSULATING BASE BEING PROVIDED WITH CUT-OUT PORTIONS IN THE SPACES BETWEEN SAID ELEMENTS SUFFICIENT TO BARE THE SURFACE OF SAID CONDUCTIVE SUPPORT WITHIN SAID SPACES AND CAUSE THE INSULATING BASE TO CONFORM SUBSTANTIALLY TO THE SHAPE OF THE SPACE METAL ELEMENTS.