US3747029A - Terminal resistor for waveguides and coaxial high frequency cables - Google Patents

Abstract

A terminal resistor or load for waveguides and coaxial high frequency cables; the resistor being formed from selected electrically conductive synthetic resin materials. Such resistors or loads being distinguished by being frequency independent; meeting exacting absorption properties; and retaining its effectiveness under extreme conditions of mechanical wear and tear.

Description

United States'Patent [191 Prinzhorn [451 July 17,1973

[ TERMINAL RESISTOR FOR WAVEGUIDES I AND COAXIAL HIGH FREQUENCY CABLES [75] Inventor: Klaus Prinzhorn, Burgdorf, Germany [73] Assignee: Knbelund Metallwerke Gutenholfnungshutte Aktiengesellschaft, Hanover, Germany [22] Filed: May 10, 1972 [21] Appl. No.: 251,870

[52] U.S. Cl 333/22 R, 252/502, 252/511 [51] Int. Cl. H01]: 1/26 [58] Field 01 Search 252/502, 503, 511,

[56.] References Cited 7 9 UNITED STATES'PATENTS 2,968,775 l/196l Rose 333/22 R X 3,104,985 9/1963 Williams et a1. 252/511 X 3,155,631 11/1964 Z PP Jr 252/511 X 2,765,354 10/1956 Carpenter et 81.. 252/502 X 3,208,013 9/1965 Walker et al. 252/502 X 2,977,591 3/1961 Tanner 333/22 R X 3,036,280 5/1962 Woodcock 333/22 R 2,730,597 1/1956 Podolsky et al 333/22 R Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Saxfield Chatmon, .lr. Atlorney-Philip G. Hilbert [5 7] ABSTRACT A terminal resistor or load for waveguides and coaxial high frequency cables; the resistor being formed from selected electrically conductive synthetic resin materials. Such resistors or loads being distinguished by being.

frequency'independent; meeting exacting absorption properties; and retaining its effectiveness under extreme conditions of mechanical wear and tear.

6 Claims, 4 Drawing Figures Ill/l/l/ll/l/l/ll/l/l/l/l/l/ PAIENIEB JUL x 1 ma /1O LII/ll- TERMINAL RESISTOR FOR WAVEGUIDES AND COAXIAL HIGH FREQUENCY CABLES This invention relates to a terminal resistor which is to be used in conjunction with waveguides and coaxial high frequency cables. Such devices are particularly useful in the transmission of electromagnetic waves of very high frequency.

.Such terminal resistors or loads serve for reflectionless termination of waveguides or high frequency cables and therefore they must show minimal reflection factors, while at the same time being operable within the largest possible range of frequencies. A further requirement of such loads is that they should be largely independent of the direction of polarization and of the incidence of the impinging wave.

There are known loads which are formed of wood with rotationally symmetrical configurations such as conesor cylinders with a conical bore. These loads have a length of about ten conductor diameters, which makes them unsuitable for field use as at proving grounds, inasmuch as they are unwieldy.

Another know load device is formed of carburized paper (Bakelized paper) in strip form which cut V shaped and two of which are arranged at right angles to each other with their apex lying at the conductor wall. Such loads can not satisfy exacting requirements.

,Yet another load device known in the art is formed from a mixture of synthetic resin and carbonyl iron dust. This type of load is best suited for low reflection factors. However such load is expensive to fabricate and is quite brittle making it unsuitable for field testing,

since under adverse conditions, it fails with even small applied stresses.

Accordingly, an object of this invention is to provide an improved terminal resistor or load which is frequency independent; which shows optimum absorption characteristics; which is simple to fabricate; and which retains its effectiveness under adverse operating conditions.

A further object of this invention is to provide a terminal resistor or load of the character described, which is fabricated from an electroconductive polyethylene plastic which is of an eleastic character; the device being unaffected in its operational characteristicsunder extreme conditions of mechanical wear and tear. Other objects of this invention will in part be obvious and in part hereinafter pointed out.

DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found that resistors or loads for wave guides or coaxial cables, formed from selected thermoplastic materials which are rendered electroconductive, show improved results in the microwave region and is highly resistant to adverse conditions of use, particularly in field testing.

Thus, the loads of the instant'invention are formed from a composition constituted of polyethylene, a polyethylene copolymer and a conductive material such as carbon black or the like.

The composition is made up of 100 parts of polyethylene, from 20 to 40 parts of a polyethylene copolymer, and from 50 to 100 parts of conductive carbon black, all by weight. Preferably 30 parts of the copolymer and parts of carbon black are mixed with the parts of polyethylene.

The copolymer may be made up of either ethyle vinyl acetate or an acrylate such as ethylene acrylate copolymerized with the polyethylene.

The resultant composition is suitably molded in the desired configuration, forming the resistor or load to be used with a wave guide or a coaxial cable.

Thus, as shown in FIGS. 1, 2, a wave guide generally indicated at 10, having a wall 11 and terminal end 12, is adapted to have associated therewith a load embodying the invention and generally indicated at 13. The load 13 may take the form of a hollow conical member 14 formed of the above described composition. A support member 15 is fixed to the base of load member 14 and removably mounted in the open end 12 of wave guide 10 for testing purposes.

Alternatively, the load of the instant invention may be applied to coaxial cables 10A, as shown in FIGS. 3, 4. Here the inner conductor is indicated at 16 and the outer conductor at 15A. The load 13A is similar to load 13, being in hollow conical form with member 14A with an apex opening 17 to pass the terminal end portion of inner conductor 16 therethrough. The member 14A is fixed to support member 15 and is mounted in the open end 12A of outer conductor 15A.

It is understood that the loads 13, 13A may take other geometrical configurations and may be solid as wellas hollow. Such loads have been found to be frequency independent, particularly in the microwave region and almost completely free of reflection so that it can be regarded as a matching load. The particular configuration of the load is related to the waves to be transmitted, that is, which and how many planes of polarization are present in the wave guide.

I claim:

1. A terminal load for means for transmitting high frequency electromagnetic waves, said load comprising a resilient member formedof a composition consisting of 100 parts of polyethylene, 30 parts of polyethylene copolymer, and 70 parts of carbon black, all by weight.

2. A load as in claim 1 wherein said copolymer is ethylene vinyl acetate.

3. A load as in claim 1, wherein said copolymer is ethylene acrylate.

4. Aload as in claim 1, wherein said member is of hollow conical shape, and further including a support member fixed to the base of said member.

5. A load as in claim I, wherein said transmitting means comprises a wave guide.

6. A load as in claim 1, wherein said transmitting means comprises a coaxial cable.

Claims (5)

1. 2. A load as in claim 1 wherein said copolymer is ethylene vinyl acetate.
2. 3. A load as in claim 1, wherein said copolymer is ethylene acrylate.
3. 4. A load as in claim 1, wherein said member is of hollow conical shape, and further including a support member fixed to the base of said member.
4. 5. A load as in claim 1, wherein said transmitting means comprises a wave guide.
5. 6. A load as in claim 1, wherein said transmitting means comprises a coaxial cable.

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