US2436284A - Coaxial transmission line - Google Patents

Coaxial transmission line Download PDF

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Publication number
US2436284A
US2436284A US718489A US71848946A US2436284A US 2436284 A US2436284 A US 2436284A US 718489 A US718489 A US 718489A US 71848946 A US71848946 A US 71848946A US 2436284 A US2436284 A US 2436284A
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United States
Prior art keywords
transmission line
inner conductor
coaxial transmission
insulating
conductor
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Expired - Lifetime
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US718489A
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English (en)
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Lewis A Bondon
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Individual
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Individual
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Publication date
Priority to FR958693D priority Critical patent/FR958693A/fr
Application filed by Individual filed Critical Individual
Priority to US718489A priority patent/US2436284A/en
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Publication of US2436284A publication Critical patent/US2436284A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • H01B11/1873—Measures for the conductors, in order to fix the spacers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S285/00—Pipe joints or couplings
    • Y10S285/909—Fluorocarbons and memory plastics

Definitions

  • This invention relates to coaxial transmission lines and has more particular reference to insulating assemblies for maintaining the conductors of such lines in concentric relation.
  • Conventional forms of coaxial transmission lines usually comprise a tubular inner conductor disposed in a tubular outer conductor and spaced concentrically therefrom by insulating spacing devices.
  • One conventional type of spacing means comprises insulating rings or discs usually made of ceramic material and mounted on the periphery of the inner conductor at intervals therealong. The rings or discs are usually secured on the inner conductor by one of the following means:
  • Another conventional type of spacing means comprises radial insulating rods or pins usually made of ceramic material and secured to the inner conductor at intervals therealong.
  • the rods or pins are usually secured to the inner conductor by one of the following means:
  • the object of all the foregoing methods of coax al line construction is to obtain a signal propagating medium having a propagating constant that is close to that provid d by air.
  • This propagation constant is reduced as soon as dielectrics having specific inductive capacity values higher than air are introduced into the propagating medium. Therefore the desirable coaxial transmission line must have a minimum mass of low dielectric body as supporting and spacing elements as will allow maximum physical and thermal performance under various service conditions for long periods of time without need for replacement or maintenance.
  • the inner and outer conductors must he maintained as accurately as possible in concentric relation throughout the transmission system in order to provide undistorted signal propagation from the signal source to the terminating elements.
  • momentary or sustained high voltage gradients exist along the line it is necessary to have this accurate concentric relation to provide a uniformly distributed electrical stress at the points of support to prevent localized dielectric heating and possible thermal failure and to prevent lower corona initiation voltages producing electrical flash-over at these points and a subsequent inoperative system.
  • Another object of the invention is to provide a coaxial transmission line, as characterized above, in which the pins and spacing members are made of insulating material of such character and are assembled in such manner as to provide great resistance to thermal and physical shock.
  • Another object of the invention is to provide a coaxial transmission line, as characterized above.
  • the spacing members and supporting pins are made of insulating materials which provide a propagating medium substantially the same as air, thus providing higher signal transmission efiiciency to permit its use at frequencies beyond the range of the conventional air dielectric coaxial transmission line.
  • Another object of the invention is to provide a coaxial transmission line, as characterized above, in which the supporting pins and the spacing members are made of insulating material of such character and are assembled in such manner as to obviate the necessity for the usual linear dimensional tol rances, thereby providing a. differential impedance. limit heretofore unobtainable for commercial application.
  • a further object of the invention is the provision of a coaxial transmission line that can be readily assembled and repaired in both factory and field and one that is relatively inexpensive tomanufacture.
  • Fig. 1 is an elevational view with parts broken away of a coaxial transmission line constructed in accordance with the present invention
  • Fig. 2 is an end view with certain parts shown in section, of the coaxial transmission line shown in Fig. 1;
  • Fig. 3 is an end view of one of the insulating spacers shown in Figs. 1 and 2;
  • Fig. 4 is an elevational view of the insulating spacer shown in Fig. 3.
  • a coaxial transmission line comprising an outer conductor l and an inner conductor l l.
  • the conductors are held in concentric relationship, throughout their length, by means of longitudinally spaced, angularly disposed insulating spacing assemblies mounted on the inner conductor.
  • Each insulating assembly comprises a diametrically opposed pair of spacing members or caps l2 interposed between the inner and outer con ductors and engaging diametrically opposed sections on the inner surface of the outer conductor and held in position by means of an elongated pin l3 extending through diametrically opposed holes H-il formed in the inner conductor with its projecting ends
  • Each of the caps I2 is identical in construction and, in the particular embodiment illustrated, is shown as a cylindrical member having a coaxial cylindrical recess l6 provided with a conically shaped bottom I! formed therein.
  • One end of the cylinder is wedge-shaped, as indicated at l8, and the other end is made concave, as indicated at IS, with a surface curvature the same as the outer surface curvature of the inner conductor.
  • the caps are preferably made of a compressible plastic organic insulating material such as polytetrafiuoroethylene. This is an extremely lowloss material. It is physically capable of maintaining operating efliciency at the elevated temperatures encountered in normal service and is also physically capable of maintaining intimate contact with the conducting surface of the inner conductor throughout the service life of the line. Cap members made of this material will not carbon-track on flash-over and do not require surface impregnating treatments to reduce its moisture absorption factor as the material is normally nonhydroscopic.
  • Each of the pins I3 is identical in construction and in the particular embodiment illustrated is shown as an elongated cylindrical member having conically shaped ends l5-l5.
  • the pins are made of an organic insulating material, The material preferred is a thermosetting styrene copolymer such as ethyl vinyl benzine div nyl ben- 4 zene styrene copolymer. Such a copolymer is disclosed in U. 8. Patent No. 2,256,160, issued Septempber 16, 1941.
  • the pins may also be made of methyl methacrylate or of ceramic material composed principally of magnesium oxide. Pins made ofthe foregoing named materials are not subject to deformation, cracking or plastic flow.
  • the diameters of the pins are such that they fit tightly in the holes i6, I4 formed in the inner conductor to eliminate any air therebetween.
  • the pins are approximately one-half the diameter of the caps and approximately one-fourth the diameter oi. the inner conductor.
  • the supporting pins i3 are fitted in the openings i4, H in the inner conductor. Then, the caps 12 with their wedge-shaped ends positioned longitudinally, are press-fitted onto the projecting ends of the pins and against the outer surface of the inner conductor.
  • each cap provides an intimate physical air-tight saddle fit with the outer surface of the inner conductor, as indicated at 20. Then, the inner conductor, with the spacing assemblies in place, is press-fitted into the outer conductor, the plastic material of which the cups are made being slightly compressed to make an intimate physical lit with the inner surface of the outer conductor. To facilitate the insertion of the cap member into the outer conductor, the longitudinal ends of the wedge-shaped end l8 may be bevelled. as indicated at 2
  • the insulating assemblies are longitudinally spaced at desired intervals and may be disposed on the inner conductor in any desired angular relation. In the particular embodiment illustrated, they are shown as being angularly disposed relative to adjacent assemblies.
  • Spacing assemblies employing a combination of extremely low-loss dielectrics, as above set forth, and assembled in the manner described, substantially eliminate all air in the dielectric field at the points of assembly and reduce the fiux density in the electric field at these points, The elimination of air in the dielectric field at the points of assembly minimizes the probability of any local corona. formation at these points.
  • the low-loss properties of the dielectric combination at any service frequency encountered in the application of an air dielectric transmission line affords stable dielectric performance, which, with the positive centering of the inner conductor, provides a stable and continuously uniform propagating medium free from diametric discontinuities.
  • the spacing members or caps l2 being made of compressible plastic material press-fitted between the inner and outer conductors, permit the use of dimensional tolerances which cannot be effected with conventional inorganic materials without a large increase in processing cost and subsequent attendant assembly difficulties increasing the final cost.
  • a coaxial transmission line constructed in accordance with this invention does not require the usual linear dimensional tolerances, thus providing a differential impedance limit heretofore unobtainable for commercial application.
  • This provision will permit a wider field of application for coaxial transmission lines as such dimensional limitations restrict the development of high outer conductor along diametrically opposed lonstanding waves to less than 10% of the voltage gitudinal sections thereof and wherein said elonstanding wave ratio introduced at the signal gated insulating member is cylindrical and has source. its ends contoured to conform to the contour of
  • such a construction provides a the inner surfaces of said recesses. minimum signal attenuation for a transmission 3.
  • a coaxial transmission line as set forth in center conductor to provide an increase in radio claim 1, wherein said elongated member is made frequency conducting surface with attending inof ethyl vinyl benzine divinyl benzine styrene cocrease in power handling capacity. polymer.
  • a coaxial transmission line comprising tubuhas been provided a coaxial transmission line lar inner and outer conductors and spacing ashaving an impedance and providing a propagatsemblies radially disposed within said outer coning medium substantially the same as that of a ductor at predetermined spaced points throughtheoretical coaxial transmission line of the same out its length for maintaining said conductors in dimensions in which the inner conductor is supconcentric relation, each of said assemblies comported solely by air.
  • a coaxial transmission line comprising tubuconductor, and an elongated cylindrical pin exlar inner and outer conductors and spacing astending diametrically through Said n r semblies radially. disposed within said outer conductor and having its ends press-fitted into the ductor at predetermined spaced points throughrecesses formed in said cap members, said pin out its length for maintaining said conductors in being made of ethyl vinyl benzene v ny benconcentric relation, each of said assemblies comzene styrene c D Y and having t 011- prising a pair of diametrically opposed insulating g toured to conform to the contour of the inner members press-fitted between the inner surface surfaces of said recesses.

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US718489A 1946-12-26 1946-12-26 Coaxial transmission line Expired - Lifetime US2436284A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
FR958693D FR958693A (enrdf_load_stackoverflow) 1946-12-26
US718489A US2436284A (en) 1946-12-26 1946-12-26 Coaxial transmission line

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US718489A US2436284A (en) 1946-12-26 1946-12-26 Coaxial transmission line

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US2436284A true US2436284A (en) 1948-02-17

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US (1) US2436284A (enrdf_load_stackoverflow)
FR (1) FR958693A (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2676198A (en) * 1950-08-31 1954-04-20 Rca Corp Electrical connector
US2724095A (en) * 1952-10-06 1955-11-15 Us Gasket Company Sub-miniature tube socket
US2740826A (en) * 1952-07-09 1956-04-03 Product Dev Company Low capacity high temperature coaxial cables
US2785219A (en) * 1952-09-23 1957-03-12 Us Gasket Company Stand-off terminals
US3151925A (en) * 1961-10-25 1964-10-06 Lewis A Bondon Coaxial tranmission line utilizing reactance compensated, paired pintype insulator spcing assembly
US4758685A (en) * 1986-11-24 1988-07-19 Flexco Microwave, Inc. Flexible coaxial cable and method of making same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2216893A (en) * 1938-03-24 1940-10-08 Bell Telephone Labor Inc Concentric conductor transmission line
US2218921A (en) * 1938-03-24 1940-10-22 Bell Telephone Labor Inc Concentric conductor transmission line
US2256160A (en) * 1938-11-18 1941-09-16 Dow Chemical Co Making polymerized vinyl aromatic articles
US2287201A (en) * 1937-11-24 1942-06-23 Int Standard Electric Corp Electrical stress grading device
US2397568A (en) * 1944-03-11 1946-04-02 Ellsworth F Seaman Shockproof electrical resistor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2287201A (en) * 1937-11-24 1942-06-23 Int Standard Electric Corp Electrical stress grading device
US2216893A (en) * 1938-03-24 1940-10-08 Bell Telephone Labor Inc Concentric conductor transmission line
US2218921A (en) * 1938-03-24 1940-10-22 Bell Telephone Labor Inc Concentric conductor transmission line
US2256160A (en) * 1938-11-18 1941-09-16 Dow Chemical Co Making polymerized vinyl aromatic articles
US2397568A (en) * 1944-03-11 1946-04-02 Ellsworth F Seaman Shockproof electrical resistor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2676198A (en) * 1950-08-31 1954-04-20 Rca Corp Electrical connector
US2740826A (en) * 1952-07-09 1956-04-03 Product Dev Company Low capacity high temperature coaxial cables
US2785219A (en) * 1952-09-23 1957-03-12 Us Gasket Company Stand-off terminals
US2724095A (en) * 1952-10-06 1955-11-15 Us Gasket Company Sub-miniature tube socket
US3151925A (en) * 1961-10-25 1964-10-06 Lewis A Bondon Coaxial tranmission line utilizing reactance compensated, paired pintype insulator spcing assembly
US4758685A (en) * 1986-11-24 1988-07-19 Flexco Microwave, Inc. Flexible coaxial cable and method of making same

Also Published As

Publication number Publication date
FR958693A (enrdf_load_stackoverflow) 1950-03-17

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