Title:
Arrangement adapted to suppress radio frequency currents on conductors
United States Patent 2419855
Abstract:
This invention relates to means to suppress the flow of radio frequency currents on conductors, especially of the so-called "shell" waves on the outer surface of cable shielding. Contradistinct to prior practice, according to this invention, to the said end, the conductor which is to be rid...


Inventors:
Otto, Roosenstein Hans
Application Number:
US36156440A
Publication Date:
04/29/1947
Filing Date:
10/17/1940
Assignee:
Otto, Roosenstein Hans
Primary Class:
Other Classes:
333/243
International Classes:
H03H1/00
View Patent Images:
Description:

This invention relates to means to suppress the flow of radio frequency currents on conductors, especially of the so-called "shell" waves on the outer surface of cable shielding. Contradistinct to prior practice, according to this invention, to the said end, the conductor which is to be rid of radio frequency waves is built up of portions of dissimilar characteristic impedance, preferably of x/4 length rather than by the aid of a short-circuit or rejector system, with the result that the radio frequency waves are gradually attenuated completely as a result of reflections produced at the points of discontinuity of the characteristic impedance. The general and broad principle underlying the invention shall now be explained in greater detail by reference to the appended drawing as applied to the feeding of an antenna S by way of a shielded line or cable L. If the outer shell of the line were simply free-ended, this outer surface, in the light of experience, would become excited; in other words, so-called shell waves would arise and these would exercise a harmful effect upon the antenna radiation. In order to avoid the said waves, the outer sheath is composed of several pieces or portions Ai, Bi, A2, B2 of dissimilar wall thickness, and each of these possesses different characteristic impedance values. The length of these components is preferably equal to X/4. Now, if the assumption is made that at the juncture 3 of connection points of the cable K itself there still flows a vanishingly small current I, it can be demonstrated that the current at point 1=7Iy ZA and the current at point 2=-'*(' while the current at point 4 3=I. where ZB and ZA are the surge or characteristic impedances of the line portions A and B. 4 For instance, if ZA it follows that at point K flows a current equal 5o to one-twenty-seventh that at point 3; in other words, the shell wave has dropped to 1/27. If, in line with what is being shown in the drawing, there is moreover used an antenna at the base of which only a small current intake is required, in other words, for instance, a X/2 antenna, it will be seen that also the shell wave amplitude at the base end of the antenna is extremely small. If the antenna currents at points c and a are as 10:1, it follows that the amplitude of the - shell waves at point K is =1/270 the amplitude at point 3. These shell waves may be taken to be negligible for practical purposes.

The invention is not confined to the suppression of shell waves, in fact, it may generally be used for the purpose of suppressing radio frequency waves along conductors. If the length of the component parts is not made equal to x/4, then the calculation is somewhat more complicated. However, the attenuation of shell waves also in this instance is practicable in the same way as above described.

I claim: 1. An arrangement for suppressing the flow of radio frequency energy along a conductor in which said conductor is divided into a series of sections, each having a length equal to an odd multiple of a quarter of the operating wavelength, the outside diameter of said sections so 0 varying that the surge impedance of each section so differs from that of adjacent sections that a maximum reflection of energy occurs at each junction between sections.

2. An arrangement for suppressing the flow of 5 energy along the outer conductor of a concentric transmission line in which said outer conductor is divided into sections of different outside diameters such that the surge impedance of each section differs from that of adjacent sec0 tions, each having a length equal to an odd multiple of a quarter of the operating wavelength, the relationship between the impedances of adjacent sections being such as to cause a large reflection of energy at each junction between 5 sections.

3. An arrangement for suppressing the flow of radio frequency energy along the outer conductor of a concentric transmission line in which said outer conductor is divided into sections of different diameter such that the surge impedance tions whereby reflection of energy occurs at eacn Number junction between sections, each section having a 2,178,299 length equal to an odd multiple, including unity, 2,205,874 of a quarter of the length of the operating wave. 5 2,131,108 HANS OTTO ROOSENSTEIN. 1,859,390 2,236,102 REFERENCES CITED 2,184,729 The following references are of record in the 10 2,127,088 file of this patent: 2,038,240 JNITED STATES PATENTS Name Date Dallenbach ------- Oct. 31, 1939 Buschbeck --------- June 25, 1940 Lindenblad ------- Sept. 27, 1938 Green -------------- May 24, 1932 Kolster ---------- Mar. 25, 1941 Bailey ------------- Dec. 26, 1939 Percival et al.----.- Aug. 16, 1938 Schelkunoff -------- Apr. 21, 1936