US2178299A - Conductor line for ultra-short electromagnetic waves - Google Patents

Description

CONDUCTOR LINE FOR ULTRA-SHORT ELECTROMAGNETIC WAVES original Filed April 25, 1935 2 Sheets-Sheet 1 QMQQM @bt 3i, 1939. w. DLLENBACH 2,178,299

CONDUCTOR LINE FOR ULTRA-SHORT ELECTROMAGNETIC WAVES Original Filed April 25, 1955 2 Sheets sheet 2 Patented Oct. 3l, 1939 rAre-NT oFFicE CONDUCTOR LINE FOR ULTRA-SHORT ELECTROMAGNETIC WAVES Walter Dllenbach, Berlin-Charlottenburg, Germany, assignor to N. V. Machinerieenen Apparaten Fabrieken Meat, Utrecht, Netherlands Application April 25, 1935, Serial No. 18,232, Renewed May 3, 1939. In Germany April 2,7, 1934 8 Claims.

The object of the present invention consists in conductor line intended for the conduction, or

for the conduction and radiation, of ultra-short, electromagnetic waves.

In accordance with the present invention, the

conductor line is made to consist of sections forming resonance elements periodically repeatg themselves, along the length of which the surge impedance varies, and which are at least approximately tuned to the waves to be conducted or to be radiated.

With the aid of Figs. 1 to 8, examples of the present invention have been explained in detail. Fig. 1 diagrammatcally represents a vertical oss section of one form of the invention in which the resonance limitations are equivalent a Lecher system section of the length M4. Fig. 2 is a right end view of the arrangement shown in Fig. 1.

Fig. 3 diagrammatically represents a vertical cross section of one form of the invention in which the resonance limitations are equivalent a Lecher system section of the length M2. Fig. l is a right end view of the arrangement shown in Fig. 3.

Figs. 5 and 6 are vertical cross sections of two arrangements closely resembling each other and which are adapted for the conduction of electromagnetic waves of certain natural frequency.

Fig. 7 is a vertical section of an arrangement which serves simultaneously for the conduction and radiation of electromagnetic waves.

Fig. 8 is a plan view of a plurality of the devices of Fig. 7 arranged in a single plane to form an aerial system.

In Figs. l and 2 two circular-cylindrical tube parts i. and 3, being joined at i, have been disposed concentrically round a circular-cylindrical inner conductor i Let it be assumed that the lengths of the tube ctions 2 and 3 are w1 and x2 respectively and that their wave resistance, that is the surge impedance is W1 and W2 respectively. If

0 E1 at the end of the section x1, at the most negligible ohmic resistance, is expressed by the iollowing two equations:

(Cl. Z-11) wherein 7' designates the imaginary unit The distribution of current and potential E and J appearing at this condition of resonance along the conductor l, has also been represented 0 in Fig. 1. At the ends potential loops are formed in the same way as with a resonator of the length M2, whilst near the centre a potential node is produced.

In the same manner as in Fig. 1 a resonance element, being equivalent to the length M, is represented, Figs. 3 and 4 show a resonance element equivalent to a Lecher system sector of the length 'y/4. If W1 and W2 signify again the surge impedances corresponding to the two different 40 parts, the reduced lengths 1 and 2 have, in the condition of resonance, to meet the following relation:

pared with a homogeneous Lecher system, that is, as compared with a Lecher system with invariable surge impedance along its line axis, an arrangement of the kind mentioned above possesses, however, excellent properties. Owing to the periodically varying surge impedance, it represents a hindrance to the propagation of running waves, with the exception of those waves for which the resonance elements are excited in their natural frequency. For such wavelengths the arrangement acts in the nature `of a lter chain. The separate resonance elements are, as a matter of fac-t, excited in their natural frequency, passing on the excitation by means of the coupling existing between them. The excitation in the resonance frequency does not take place for a frequency, which with its natural frequency does V4not at least approximately coincide with the resonance elements serving for the construction of the arrangement. ment proves to be impermeable to those frequencies more strongly deviatng from the resonance frequency. This suppression effect will be all the more accentuated, the larger the number of resonance elements are joined together.

A resonance tuning for an assumed frequency will also then be possible in arrangements in accordance with Figs. 1 and 2 or Figs. 3 and 4, if one of the tube sections, for example, the tube section 3 or 5, has been omitted. In this case, the freely projecting end of the inner conductor i or 5 will radiate. The resonance element will then exhibit a certain damping, its intensity be ing proportional to the length of the freely projecting end.

It is obvious, that by joining such resonance elements, partly radiating freely, arrangements may be produced which are acting like an aerial system with directional characteristic.

Fig. 5, for instance, represents an arrangement for the conduction of ultra-short electromagnetic waves, produced by a series connection of resonance elements as disclosed in Figs. 1 and 2. In contra-distinction to the arrangement disclosed in Figs. l and 2 the difference in the surge impedance is produced along the two sections :r1 and x2 by changing the radius of the inner conductor. If it is assumed, that this arrangement is fed at one end at 9 with the resonance frequency of the elements for the purpose of transmitting ultra-short, electromagnetic waves, every resonance element situated between two consecutive faces l in a stationary wave, will be excited in such a manner that, with one section of the Lecher system it will be equivalent to the length M2, as this has been represented graphically in Fig. by the potential E and the current J. The other end Il may be coupled in a suitable manner with a loading resistance for example a radiator. The operation of the arrangement will then resemble that of a filter chain interpolated between a generator and a load.

' An arrangement, identical with that shown in Fig. 5, is illustrated in Fig. 6. The resonance elements, being equivalent to a length M2 and shown in Fig. 6, each consist of a bi-lateral plate condenser I2 connected in series with a cylindrical condenser I3. The plate condcnsers consist of circular plates or disks I4 attached to the inner conductor, said plates or disks being sur-v rounded by a jacket. Owing to the radial extension of one of the sections of the resonance element, a considerable reduction of the length of the arrangement will be attained. 'I'he plate condensers .are not acting in this instance as pure The arrangecapacities, but as conductors with capacity and self-induction, in which not only currents, but also potentials are dependent upon the radius.

Fig. 7 represents an arrangement which is produced by means of the series connection of resonance elements equivalent to a length M4 in accordance with Figs. 3 and 4. Deviating from Figs. 3 and 4, however, the external jacket, surrounding the section mi of each resonance element, has in each case been omitted, so that the section or portion ofthe inner conductor, corresponding to the length mi, is adapted to radiate freely. In order to procure the requisite transition for the current in the external conductor, which is inversely equal to the current in the freely radiating section or portion of the inner conductor, the edges of the outer conductor, adjoining the freely radiating sections of the inner conductor, are provided with disks l5 disposed approximately perpendicular to the axis of the conductor. Between these disks I5, the current is made to pass over capacitatively and it is also between these disks that the radiation, emitted by the inner conductor, escapes in a direction perpendicular to the axis of the conductor. The freely radiating portions or sections of the inner conductor are situated, as may be gathered from the diagram representing the currents and potentials, in the proximity of the current loops of the stationary waves. The radiation elds of these separate, freely radiating portions or sections of the inner conductor, acting similarly to Hertzian dipoles, are now interfering with each other and produce a resultant directional characteristic, which may be calculated in the usual manner from the radiator diagram of the separate radiatorsand the special disposition of the diiferent radiators.

If it is considered, that by means of a suitable selection of the surge impedances W1 and W2, the lengths mi and x2 are freely selective within the limits determined by the abovementioned formulae, it follows, that the relative, special disposition of the separate radiators may be varied within wide limits for the purpose of attaining a desired directional characteristic of the entire aerial arrangement. A modified special constructional feature of the inventive idea will be found in the fact, that freely radiating portions or sections of the inner conductor will be found only in the positive loops of the current. The outer conductor will thus not be interrupted in the negative loops of the current, but will be continuously conducted. According to such modification of Fig. '7 an aerial arrangement will then be formed in which all the freely radiating portions or sections of the inner conductor are eX- cited co-phasally, following each other at intervals which are greater than M2, being positioned in the proximity of k. The resultant directional characteristic of such an arrangement with a sucient number of separate radiators, insures an extremely accentuated compression of the radiation energy in a plane perpendicular to the axis of the conductor.

In order to obviate parasitic oscillations on the outside of the separate sections or portions of the external conductor shown in Fig. 7, special collars or disks I6 may be mounted on the latter, intended to detune the outside of the corresponding section or portion of the external conductor relatively to the working frequency.

It is not necessary to employ two concentric conductors as an energy line, as it has been represented in Figs. 1 to 7, Two conductors, placed side by side and parallel to each other, may also be used. It will further be possible without any difficulty whatsoever to assume, instead of the irregular variations of the surge impedance represented in the Figs. l to 7, any desired regular variation along the length of the resonance element.

For the purpose of producing an interference, as accentuated as possible, of the radiation field oi the separate radiators, it is advisable to design the sections or portions of the inner conductor, acting as separate radiator, so that they are short when compared to the non-radiating sections or portions.

A plurality of aerial arrangements, corresponding to Fig. 7, can be combined side by side in one and the same plane so as to form an aerial system which will then, as known for aerials of the length, M2, ensure a punching of the waves around an axis perpendicular to the plane of the aerial system. Such an arrangement is shown in Fig. 8. The numerals 2i?, 2i, and 22 designate radiator systems which are individually shown in detail in Fig. 7.

t is, furthermore, possible, to assemble Yaerial systems formed by the combination of separate radiators of the kind described, with reflectors known per se.

What I claim is:

1. A structure for radiating ultra-short electric waves comprising a plurality of connecting sections, each of said sections having an inner conductor and an outer conductor of less length and partially enclosing said inner conductor, and

, plates extending substantially normal to said conductors secured to the ends of said outer conductor.

2. A directional radiating aerial system formed of a series of radiating elements, each of said elements comprising a plurality of connecting sections, each of said sections having an inner conductor and an outer conductor of less length and partially enclosing said inner conductor, and plates extending substantially normal to said conductors secured to the ends of said outer conductor, said conductors of said elements being in substantial alignment with each other.

3. A structure for conducting or radiating ultra-short electric waves comprising a plurality of equal sections forming resonance elements individually tuned substantially to a desired operating wave length, each of said sections being composed of at least two conductors spaced from each other and forming at least two units diiering from each other in their respective wave resistances, said conductors comprising an inner conductor and an outer conductor, and said outer conductor being shorter than one-fourth a wave length in each section in the proximity of a current loop whereby the inner conductor radiates.

4. A structure for conducting or radiating ultra-short electric waves comprising a plurality of equal sections forming resonance elements individually tuned substantially to a desired operating wave length, each of said sections being composed of at least two conductors spaced from each other and forming at least two units diiering from each other in their respective wave resistances, said conductors being composed of concentric cylindrioal tubes, each section having a length equal to substantially one-half a wave length, and the outer conductor being approximately three quarters the length of the inner conductor, whereby current loops are formed in spaces between adjacent outer conductors, and potential loops are formed midway of said spaces.

5. A structure for conducting or radiating ultra-short electric waves comprising a plurality of equal sections forming resonance elements individually tuned substantially to a desired operating wave length, each of said sections being composed of at least two conductors spaced from each other and forming at least two units difiering from each other in their respective Wave resistances, said conductors being composed of concentric cylindrical tubes, each section having a length equal to substantially one-half a wave length, and the outer conductor being approximately three quarters the length of the inner conductor, whereby current loops are formed in spaces between adjacent outer conductors, and potential loops are formed midway of said spaces, and collars attached to the outer surfaces of said outer conductors to detune said surfaces relative to the conducted waves whereby parasitic oscillations are eliminated.

6. A structure for radiating ultra-short waves comprising an inner and an outer concentrically disposed conductor,l said outer conductor being composed of a plurality of units, said units of said outside conductor being spaced from each other at intervals substantially equal to a half wave length, or a multiple thereof, to provide openings the length oi which in the direction of the axis of said conductors is less than one-fourth of a Wave length, and electrically conducting surfaces extending from the edges of said units adjacent said openings at an angle to the axis of said conductors.

7. A structure as in claim 6, and collars secured to each unit of the outer conductor to detune the surface thereof relative to conducted waves whereby parasitic oscillations are eliminated.

8. A structure for radiating ultra-short waves comprising an inner and an outer concentrically disposed conductor, said outer conductor having spaces therein at intervals substantially equal to a half wave length, or a multiple thereof, the length of said spaces in the direction of the axis of said conductors being less than one-fourth of a wave length, and electrically conducting surfaces extending from the edges of said spaces at an angle to the axis of said conductors.

WALTER DLLEN'BACH.

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