US2138906A - Feeder and the like for electric currents of high frequency - Google Patents

Feeder and the like for electric currents of high frequency Download PDF

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Publication number
US2138906A
US2138906A US100986A US10098636A US2138906A US 2138906 A US2138906 A US 2138906A US 100986 A US100986 A US 100986A US 10098636 A US10098636 A US 10098636A US 2138906 A US2138906 A US 2138906A
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US
United States
Prior art keywords
aerial
feeder
sheath
impedance
conductor
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US100986A
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English (en)
Inventor
Cork Edward Cecil
Pawsey Joseph Lade
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EMI Ltd
Electrical and Musical Industries Ltd
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EMI Ltd
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Filing date
Publication date
Application filed by EMI Ltd filed Critical EMI Ltd
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Publication of US2138906A publication Critical patent/US2138906A/en
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P5/00—Coupling devices of the waveguide type
    • H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
    • H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced lines or devices with unbalanced lines or devices
    • 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
    • Y10S285/906—Equivalents

Definitions

  • This invention relates to aerial systems for electric currents of high frequency such as are encountered in television and like transmission or receiving systems.
  • the length of the aerial for high frequency transmission or reception is one-half of the operating wavelength, but in some cases, in order to avoid excessive size of aerial or for other reasons, it may be desirable to employ an aerial of less length than half of the operating wavelength.
  • the impedance of the aerial at the point to which the feeder is attached contains a reactive component.
  • the mag-' 'nitude of the reactive component also depends upon the folding or shaping, if any, of the aerial.
  • transforming device is still generally required for matching purposes.
  • a transforming device in which one of the conductors of the feeder is provided for part of its length equal to a quarter of the operating wavelength and adjacent the aerial end of the feeder, with a radius greater or less than the radius of the main part of the conductor so that such portion has a characteristic impedancedifferent from that of the main part of the feeder, such characteristic impedance being arranged to give impedance matching between the feeder and the aerial attached thereto.
  • a high frequency aerial system in which a dipole aerial is fed by a concentric feeder comprising an inner conductor surrounded by a sheath and in which a rejector circuitis employed comprising an auxiliary conductor attached at one end to the sheath, the two portions of the aerial being effectively connected to the sheath and auxiliary conductor, and wherein, for the purpose of matching the impedance of the aerial to that of the feeder, the auxiliary line comprising the sheath and auxiliary conductor is arranged to function as a transformer.
  • the auxiliary conductor functions in the manner described in the specification of the above numbered patent as a rejector, and also functions, in conjunction with the sheath of the feeder, as a transformer for matching purposes, so that the use of a separate transforming device, such as the transformer disclosed in the aforesaid specification, or another form of transformer, is avoided.
  • the required transforming action may be obtained by connecting a dipole aerial topoints on the sheath of the feeder and the auxiliary conductor at a suitable distance from the end of the feeder, or by connecting the aerial to the ends of the feeder and auxiliary conductor and by adjusting the length of the auxiliary conductor.
  • Other examples of the invention will be hereinafter described.
  • Fig. 1 illustrates an aerial system constructed in accordance with one embodiment of the invention
  • Fig. 2 represents the equivalent electrical circuit of the arrangement shown in Fig. 1;
  • FIG. 3 illustrates a further aerial system in accordance with the invention
  • Figs. 4 and 5 illustrate, respectively, another embodiment of the invention and the equivalent electrical circuit
  • Fig. 6 illustrates a modification of the system shown in Fig. 4.
  • the aerial system comprises a concentric feeder including a tubular sheath 3 and an inner conductor 4, the feeder at the right hand end of Fig. 1 being adapted to be connected to a short wave wireless transmitter or receiver.
  • a concentric feeder including a tubular sheath 3 and an inner conductor 4, the feeder at the right hand end of Fig. 1 being adapted to be connected to a short wave wireless transmitter or receiver.
  • an auxiliary conductor 5 is attached to the sheath 3, the conductor 5 preferably being of the same external cross section and shape as the sheath 3, but may be otherwise constructed as described, for example, in the specification of the aforesaid patent.
  • the auxiliary conductor projects perpendicularly a short distance, for example, one or two inches from the sheath 3, and is then bent to lie parallel to the sheath 3, the free end of the auxiliary conductor being located adjacent the end of the sheath 3.
  • the free end of the auxiliary conductor 5 is conductively connected by a conductor 6 to the inner conductor of the feeder.
  • the sheath of the feeder. and the auxiliary conductor form an auxiliary transmission line shorted at one end and connected to the feeder.
  • the arrangement shown in Fig. 1 is illustrated in conjunction with a dipole aerial and the portions 1 and 8 of the aerial are connected'to the sheath 3 and the auxiliary conductor 5 at points located at a suitable distance from the end of the feeder.
  • an impedance which is a function of the impedance of the aerial and its point of attachment.
  • the effective impedance at the aerial end of the feeder is equal to the characteristic impedance of the feeder.
  • the impedance looking along the feeder from the end thereof which is connected to the transmitter or receiver is then equal tothe characteristic impedance of the feeder.
  • the action of the auxiliary conductor in conjunction with the sheath of the feeder is, therefore, that of a transformer.
  • Z1 be the characteristic impedance across the sheath 3 and auxiliary conductor 5, constituting the rejector, considered as part of a continuous line.
  • Z0 be the characteristic impedance between the inner conductor and the sheath of the feeder.
  • Points AA are connected to the feeder, which is a substantially pure resistance of value Z0.
  • the feeder which is a substantially pure resistance of value Z0.
  • To match andtune the aerial it is necessary to make the impedance at the terminals BB, without the equivalent aerial circuit connected, equal to a resistance R in parallel with a reactance X, in order to match the resistance R of the antenna and tune out the reactance +XI of the antenna. This is done by correct choice of the electrical lengths 91 and 92 of the portions AB and BC of At the other, or aerial end of the .7
  • the conditions for tuning and matching are respectively:
  • Equation 6 determines 91, and hence the distance from A at which the aerial is to be connected. Substituting this value of 91 in Equation 2 the value of X1 at BB is found. Inserting this and X in Equation 4 X2 is found and from 3 the value of 92 that is to say the length BC for the assumed value of Z1 is determined.
  • Equation 6 shows that since sin 91 can Vary between the values 0 and 1, R must lie between the limits Z0 and Z1 /Zo.
  • Z1 has an assumed value and 91 and 92 are determined.
  • FIG. 1 In the system of Fig. 1 transformations are limited to aerials with effective parallel resistances between Z and Zl /Z0.
  • Fig. 4 is shown an alternative scheme in which the, aerial and feeder points of connection are interchanged with respect to those of Fig. 1.
  • the portions 1 and 8 of the aerial are connected to the free end of the sheath 3 and auxiliary conductor and the central conductor 4 is tapped by virtue of conductor 5 onto auxiliary conductor 5 at a predetermined distance along its length.
  • aerials having an effective parallel resistance outside the above range and any value of reactance can be transformed.
  • This arrangement will also transform aerials with resistances within the above range provided that the reactance is greater than a value dependent on the resistance.
  • the equivalent electrical circuit is shown in Fig. 5 and it is possible to calculate the value of 91 for values of R, X and Z1, i. e., the length AB is determined.
  • the length of BC is again calculated to cancel the resultant reactance at BB.
  • a simpler practical arrangement is shown in Fig. 6.
  • a length of feeder 3 a whole number of half wavelengths long, and therefore acting as a 1/ 1 transformer, is slidably connected to the conductors 3a and 5 forming the line of characteristic impedance Z1.
  • the distance AB is adjusted until the equivalent parallel resistance measured at D is equal to the feeder impedance Z0.
  • a shorting member 9 which is the equivalent of the perpendicular portion of the auxiliary conductor 5 of Figs. 1, 3 and 4, and which can be suitably clamped in position, is then adjusted until the parallel reactance at D is tuned out.
  • the feeder is thus matched and may, therefore, be continued for any length.
  • concentric feeder employed herein means a feeder of the kind in which one or more conductors are surrounded by an outer conductor in the form of a sheath.
  • the sheath may,
  • a high frequency aerial system in which a dipole aerial is fed by a concentric feeder comprising an inner conductor surrounded by a sheath and in which a rejector circuit is em ployed comprising an auxiliary conductor attached at one end to the sheath at a point intermediate the ends of said sheath, the two portions of the aerialbeing effectively connected to the sheath and the auxiliary conductor at predetermined points on the lengths thereof away from their open ends for the purpose of matching the impedance of the aerial to that of the feeder.
  • a high frequency aerial system in which a dipole aerial having a complex load impedance is fed by a concentric feeder comprising an inner conductor surrounded by a sheath and in which a rejector circuit is employed comprising an auxiliary conductor attached at one end to the sheath, the two portions of the aerial being effectively connected to the sheath and auxiliary conductor, said auxiliary. conductor comprising two parallel conducting tubes open at least at one end, the two portions of the aerial being effectively connected to said tubes at said open end thereof, a.
  • short-circuiting strap connected across said tubes for adjusting the effective length thereof, said inner conductor being connected to one of said tubes at a predetermined point along its length between said strap and said open end, whereby the impedance of said aerial is matched to the impedance of said feeder.
  • a high frequency aerial system in which a dipole aerial having a complex load impedance is fed by a concentric feeder comprising an inner conductor surounded by a sheath and in which a rejector circuit is employed comprising an auxiliary conductor attached at one end to the sheath at a point intermediate the ends of said sheath, the two portions of the aerial being effectively connected to the sheath and the auxiliary conductor at predetermined points in the lengths thereof away from their open ends, and a connection joining the open end of said auxiliary conductor and said inner conductor, whereby the impedance of said aerial is matched to that of said feeder.
  • a high frequency aerial system in which a dipole aerial having a complex load impedance is fed by a concentric feeder comprising an inner conductor surrounded by a sheath and in which a rejector circuit is employed comprising an auxiliary conductor attached at one end to the sheath at a point intermediate the ends of said sheath, the'two portions of the aerial being effectively connected to the sheath and auxiliary conductor at the open ends thereof, said inner conductor being connected to the auxiliary conductor at a predetermined point along its predetermined length away from its open end, said auxiliary conductor and said sheath having such lengths and being so constructed as to form a tank circuit and functioning in the manner of a transance of the aerial to that of" the feeder.
  • a high frequency aerial system comprising a dipole aen'al having a complex load impedance, a concentric feeder having an inner conductor surrounded by a sheath, and a line for matching the impedance of said aerial to that of said feeder, said line constituting an auxiliary conductor and the outer surface of said sheath, said auxiliary conductor being coupled at predetermined points in its length both to said inner conductor and to said sheath, the two portions of said aerial being effectively coupled both to said sheath and to said auxiliary conductor, whereby the impedance of said aerial is matched to that of said feeder.
  • a high frequency aerial system in which a dipole aerial is fed by a concentric feeder comprising an inner conductor surrounded by a sheath and in which a rejector circuit is employed comprising an auxiliary conductor attached at one end to the sheath at a point intermediate the ends of said sheath, the two portions of the aerial being efiectively connected to the sheath and the auxiliary conductor at predetermined points on the lengths thereof away from their open ends for the purpose of matching the impedance of the aerial to that of the feeder, the lengths of said sheath and auxiliary conductor to the left and right of said predetermined points being so chosen as to make the aerial conductance equal to the conductance between the predetermined points and the aerial susceptance equal and opposite to the susceptance between the predetermined points.
  • a high frequency aerial system in which a dipole aerial is fed by a concentric feeder comprising an inner conductor surrounded by a sheath and in which a rejector circuit is employed comprising an auxiliary conductor attached at one end to the sheath at a point intermediate the ends of said sheath, the two portions of the aerial being effectively connected to the sheath and the auxiliary conductor at predetermined points on the lengths thereof away from their open ends for the purpose of matching the impedance of the aerial to that of the feeder, said aerial having an former for the: purpose of matching the impedjefi'ective parallel resistance in the range between Z and Z1 /Zo, where Z0 is the characteristic im pedance between the inner conductor and sheath of the concentric feeder and Z1 is the value of the characteristic impedance across the sheath of the feeder and the auxiliary conductor.
  • Means for matching a balanced complex load impedance to a coaxial line having a certain characteristic impedance comprising a section of two-conductor line, one end of which is open and the other end of which is short circuited, part of said two-conductor line acting as the outer conductor of a portion of said coaxial line, connections from one of said impedances to the open end of said two-conductor line and connections from the other impedance to a pair of points on said two-conductor line between which the admittance is equal to the conjugate of the admittance of said last named impedance, the length of said two-conductor line being so chosen as to provide such a point.
  • Means for matching a balanced complex load impedance to a coaxial line having a certain characteristic impedance comprising a section of two-conductor line, one end'of which is open and the other end of which is short circuited, a part of said two-conductor line having electrically the same potential as the outer conductor of said coaxial line, connections from one of said impedances to one end of said two-conductor line and connections from the other impedance to a pair of points on said two-conductor line between which the admittance is equal to the conjugate of said admittance to said last named impedance, the length of said two-conductor line being so chosen as to provide such a point.
  • a symmetrical tank circuit devoid of concentrated reactance, connections for energizing it from an unbalanced line, connections from said tank circuit to a balanced load circuit, the tuning of said tank circuit and the points of connection being so chosen as to match the impedance of said line to said load.

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  • Details Of Aerials (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
US100986A 1935-09-17 1936-09-16 Feeder and the like for electric currents of high frequency Expired - Lifetime US2138906A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB25815/35A GB462911A (en) 1935-09-17 1935-09-17 Improvements in and relating to feeders and the like for electric currents of high frequency

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US2138906A true US2138906A (en) 1938-12-06

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US (1) US2138906A (de)
DE (1) DE890821C (de)
GB (1) GB462911A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2456679A (en) * 1941-05-05 1948-12-21 Emi Ltd High-frequency impedance bridge
US2530048A (en) * 1950-11-14 Unbalanced-to-balanced impedance
US2634371A (en) * 1953-04-07 Multichannel antenna system
US2702345A (en) * 1949-08-25 1955-02-15 Walter Ludwig Radiation and interception of electromagnetic waves
US5296823A (en) * 1992-09-04 1994-03-22 James Dietrich Wideband transmission line balun

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE969386C (de) * 1941-01-01 1958-05-29 Pintsch Bamag Ag Frequenzabhaengiger Blindwiderstand fuer ultrakurze Wellen

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2530048A (en) * 1950-11-14 Unbalanced-to-balanced impedance
US2634371A (en) * 1953-04-07 Multichannel antenna system
US2456679A (en) * 1941-05-05 1948-12-21 Emi Ltd High-frequency impedance bridge
US2702345A (en) * 1949-08-25 1955-02-15 Walter Ludwig Radiation and interception of electromagnetic waves
US5296823A (en) * 1992-09-04 1994-03-22 James Dietrich Wideband transmission line balun

Also Published As

Publication number Publication date
GB462911A (en) 1937-03-17
DE890821C (de) 1953-09-21

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