US2343475A - Transmission line - Google Patents

Description

March 1944- H. J. R. VON BAEYER ETAL 2,343,475

TRANSMISSION LINE Filed Nov.. so, 1940 Fly]: F 42 F193 11V VE/V T 0R5 l/AMS' IA/(0B BITTER VON BAEYER,

HANS 07'7'0 ROOSENSTEIN A/VD FRIEDRICH TISCHER ATTORNEY.-

tion with Figure l. are able to arise.

Patented Mar. 7, 1944 mans'mssron me Hans Jakob Bitter von Buyer, Hans Otto Roooenstein, and Friedrich Tiecher, Berlin, Germany; vested in the Property Custodian- Application November 30, 1940, Serial No. access In Germany June 21, 1939 2 Claims. (01. 178-40 To suppress the so-called shell waves traveling along the outer conductor of shielded radio frequency lines or cables the use of stopper pots or traps has been suggested in the prior art.

These essentially consist of a metallic cylinder of .4

M4 length surrounding the outer conductor and unilaterally connected withit. Where relatively long waves are dealt with the geometric dimensions of these traps turn mostly out to be so large that constructional difficulties arise. It is, moreover, desirable in many instances to insure an excluder or suppressoraction only at a single point and to alter the line as little as possible otherwise. To the said end, according to the invention, a concentrated or lumped capacity is used with the trap, with the result that the other dimensions of the excluding structure are diminished to such-an extent that the geometric proportions of the excluding trap become far less than Ale, indeed, they can be reduced practically to any desired extent.

' There are quite a number of different ways and means adapted to carry the basic idea of the invention into effect, and some of these shall be hereinafter described by reference to. the appended drawing in which Figure 1 shows an exempliiied embodiment of the invention, while Fig-3 Figure 1 shows a coaxial line L. The inner conductor thereof terminates in an antenna A.

is arranged a plate P which, together with the upper wall of the trap, forms a capacity suflicient to tune the trap to the wave which it is In order to avoid waves travelling along the shell pr outer conductor, a trap is provided at a distance of M4 below the end of the outer conductor as indicated at T. This trap essentially comprises a concentrated or lumped capacity C and a small cup-shaped part S. By shifting the said part S having a capacitive flange, it is possible to tune the trap. This arrangement still carries current on the top face of the upper capacity flange from the line (arrow), and this current is suppressed to zero value only at the entrance end of the trap, that is to say, on the outer edge. If, also, this current is to be suppressed, and if a current anti-loop or node is to be established directly at the conductor, then the arrangement shown in Figure 2 will prove of greater advantage in which the input of the trap circuit is arranged directly on the conductor surface or in such a 'way that no currents of the kind mentioned in connec- The upper trap circuit in Figure 2 is constituted by a shell portion 51 connected at its lower edge to the con.- ductor and having a narrow gap between its upper edge and the conductor. Within the. trap S1 desired to suppress. A lower trap S2 in Figure 2 is similar to the upper trap S1 just described, with the exception that it'is entirely physically separated from theconductor. An annular space between the trap S: and the conductor-is provided, its thickness being small compared to the operating wavelength.

Figure 3 shows at the same time various ways of designing the suppressor pots or traps com- .prisinglumped capacity.

from a distance that is small compared with the wavelength. The trap is, in the latter case, .entirely separated from the transmission line and is readily shifted therefrom. The traps in the the upper portion of Figure 3 amount to subshaped concentrated capacity for tuning. If this circuit is to be made tunable, then recourse may be had to the embodiment of a trap shown fur- In this embodiment the ringcomther below. prises two parts being shiita-ble in each other. The toroidal chamber B is arranged with a slidstantially a single turn toroid having a flange able joint J on its inner side opposite thecapac ity flangesF. It will be readily apparent that this particular modification may be tuned to various operating frequencies by sliding the joint J to decrease or increase the space between flanges described with reference to Figure 1. The upper portion S3 is a second flanged cup arranged with the flange facing the flange of the cup-shaped trap S. This modification may conveniently be tuned to the frequency to be suppressed by slid- .ing the'two portions thereof further apart or closer together as may be necessary.

The selectivity ofth'e traps described is substantially greater than that of the stopper sysan easy matter to insure the desired accuracy of tuning. If an entire frequency band or a number of frequencies are to be excluded rather than a single frequency, then a plurality of traps tuned to different waves may be mounted in sequence.

Thisisillustratedbywayofexampleinrigures no further explanation is required, the traps I,

2 and I being of different sizes so that each suppresses a different frequency.

The tuning and the properties of the trap or relationship with respect to said pot circuits may be acted upon and regulated at will by filling the same with materials possessing convenient dielectric constants, permeability, and

, conducting powers. In fact, a medium inhering adequate loss may here serve at the same time to directly attenuate and suppress the wave to be eliminated. In an embodiment of this kind, for instance, a hemp rope may be wrapped or braided with wires in such a way that two semi-cylindrical cups placed opposite each other are formed. This rope being tuned to resonance by its diameter maybe wrapped around the conductor to be rid of radio frequency waves thus resulting in an arrangement resembling that shown on top in Figure 3, though with this distinction that a substantial ohmic drop is occasioned. A further modification involves a lumped capacity connected across the ends of a toroidal coil surrounding the transmission line. The toroidal coil may be conveniently constructed by lacing a We claim:

1. A wave trap mounted about a conductor and spaced from the outer surface thereof to suppress the traveling along theconductor of waves of a particular high frequency comprising, an annular shell formed of two co-extensive cylindrical portions of diilerent diameters the smaller of which is larger than and spaced from the outer surface of said conductor, a first annular plate connecting said cylindrical portions 'at one end, a second annular plate similar to said flrst'annular plate and positioned at the opposite end of said cylindrical portions and connected to the larger of said cylindrical portions, said second annular plate being spaced at its inner periphery from the adjacent end of the smaller of said cylindrical portions, and an annular condenser plate within said shell connected at its inner periphery to the end of the smaller of said cylindrical portions adjacent said second annular plate and spaced parallel to and in predetermined second annular plate, whereby said condenser plate and said second annular plate constitute a condenser of predetermined characteristics, said shell having radial and axial dimensions whereby the trap is tuned to the desired frequency.

2. A wave trap to suppress the traveling along a conductor path of waves of a particular high frequency wherein the conductor path is along a cylindrical conductor, the combination with said conductor of, an annular shell mounted about said conductor and formed by a cylindrical member spaced from said conductor and a pair of conductor around a wooden ring adapted to be I placed over the transmission line.

The invention is not confined to the purpose of eliminating or suppressing what has briefly been called shell waves, in fact, it can be used also to suppress waves of definite frequency on any kind of conductor at all. From other constructions known in the prior art it distinguishes itself especially by its extremely reduced geometrical proportions.

parallel annular plates attached at their outer peripheries to said cylindrical member, one of said annular plates being attached at its inner periphery to the conductor and the other of said annular plates being spaced at its inner periphery from said conductor to form a slit, and an annular condenser plate within said shell mounted at its inner periphery upon said conductor adjacent said slit and positioned in coacting relationship with respect to the annular plate forming said slit whereby a condenser is formed of predetermined characteristics, said shell having radial and axial dimensions whereby the trap is tuned to the desired frequency.

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