US1927393A - Transmission system for ultrashort waves - Google Patents

Description

Sept. 19, 1933.- R.-H. DARBORD 1,927,393

Y I 'rnausmssxou Sysmr FOR ULTRA-SHORT WAVES Filed July 10, 1931 -:2 SheetS-Sheej: 1

IFIG] I 1164/ INVENTOR RENE H. DARBORD ATI'OR Y I I I Sept. 19, 1933. R. H. DARBORD 1,927,393

' TRANSMISSION SYSTEM FOR ULTRA-SHORT WAVES Filed July 10, 1931 -2 Sheets-Sheet 2 FIG. 7

l2 /I/lIIII/I/Illllllll FIG. I l

r INVENTOR RENE H. DARBORD ATTORNEY \Q VARIABLE DIAMETER i Patented Sept. i9, 1.933

TRANSMISSIQN SYSTEM FOR ULTRA- SHORT WAVES York Application July 10, 1931. Serial No. 549,925 11 Claims. (QB. 250-17) My invention relates to improvements in ultra short wave transmission systems. The object of my invention is to locate a radiating element at the focus of a reflector and a tube for transmission and reception behind the reflector, thus avoiding irregular distribution of the radiation from the radiating element; and yet at the same time provide a transmission line, connecting the /tube and the radiating element, which will permit maximum transference of energy therebetween.

The transmission line, which is sectional, is composed of conductors that are adjusted by sections to neutralize the reactance of the tube and to match the resistance of the tube side (which term will be explained subsequently) with the radiation resistance of the radiating element, which may be either a doublet or antenna.

When the tube is located near the doublet and in front of the reflector, the angular distribution of radiation is irregular. This irregular distribution is caused by interference between the two sources, namely, the doublet and the external surface of the plate; and also by various connections in which the doublet induces oscillations.

This parasitic effect is avoided byplacing the tube behind the reflector and connecting it with the doublet located at the focus of the reflector by a special form of transmission line. This transmission line is composed of several sections; certain sections being so adjustable that there is a maximum transference of energy between the tube and doublet, With this arrangement of the parts of my invention, the doublet emits radiations without interference or parasitic eifects, while at the same time, since there is a maximum transference of energy to the doublet, a signal of high intensity is transmitted.

My invention is illustrated in the accompanying drawings, wherein:

Fig. 1 shows the tube and doublet placed before the surface of a reflector;

Fig. 2 shows the doublet arranged in a vertical position and also the resultant curve of radiation distribution;

Fig. 3 shows the doublet arranged in a vertical.

Fig. 6 shows the resultant curve of radiation distribution when the arrangements of Figs. 4or 5 are used;

Fig. 7 shows a modification of Fig. 4 wherein the transmission line is composed of adjustable sectional conductors;

Fig. 7A shows a sectional view of the conductor made in two parts;

Fig. 8 is a modification of Fig. '7 wherein the tube is placed in a building or but while the reflector is placed in a shelter with its focal aperture open to the atmosphere; and

Figs. 9, 10 and 11 show various modifications for adjusting the transmission lines for the purpose of altering its electrical characteristics.

Fig. 1 shows an arrangement in which the tube '1 and the doublet A are placed together before a reflector. In this arrangement the parasitic effect, mentioned above, is set up.

Fig. 2 shows the doublet A in vertical relationship to the tube '1 and the form of the curve of radiation distribution produced by this arrangement. It will be noted that the curve is unsymmetrical with respect to the axis of the reflector.

Fig. 3 shows the doublet A in horizontal relation to the tube T and the radiation distribution curve of this arrangement. It will be noted that a smooth curve is formed on the left side of the axis of the reflector, out that the curve to the right of the axis of the reflector is not symmetrical with the other portion of the curve, and also contains decided irregularities.

Fig. 4 shows the tube T separated from the doublet A by the reflector, while the tube and reflector are connected by an ordinary transmission line passing through the reflector. Although the 'transmission line is here illustrated as a two-wire system, it is to be understood that this line is typical of the ordinary transmission line.

Fig. 5 shows a similar arrangement, but one having the transmission line, which is likewise typical of the ordinary transmission line, passing 100 around the reflector and terminating in a half wave reflector.

These two arrangements, shown in Figs. 4 and 5,

avoid the parasitic effects to which reference. has

been made. The radiation distribution curve obtained by these arrangements is shown in Fig. 6. It will be noted that the curve is symmetrical on both sides of the reflector axis. This desirable curve results from the location of the tube T behind the reflector.

There is still less thanmaximum emciency with the arrangements shown inFigs. 4 and 5, even though the tube in each case is located behind the reflector. This non-attainment of maximum eiiiciency of radiation'results from the use of the I carefully constructed transmission lines is the latter percentage of transference obtained;

usually with the ordinary line the transference percentage approximates the lower amount.

In'order to avoid the usual low percentage of energy transference between the tube and the radiating element, a novel transmission line has been designed. This line permits a maximum energy transference between the tube and the radiating element, with the result that signals of high intensity are obtained from the present system.

Referring now to the transmission line of Fig. '7, the line is composed of a number of sections: ab, bc, cal and de.

The section ab has a variable effective length and slides in one end of the section be.

In addition to the method of varying the efiective length of the section ab shown in Fig. 7, there is another satisfactory method which is illustrated in Fig. 9. .The outer cylindrical conductor 12 is provided with a slot through which the handle 10 passes. This handle is attached to an inner cylindrical conductor 11. When the handle 10 is moved back and forth it causes the conductor 11 to slide back and forth within conductor 12. Conductor 13 passes through the inner conductor 11, as shown, and adjustment is made between the conductors by the movement of the conductor 11. The section ab, being variable in length, serves to annul the reactance of the generating element of the tube T, whether that reactance is of a capacitative or of an inductive character.

The section be is equal in length to an integral number of half wave lengths, and consequently the oscillations fromthe tube T are not transformed by this section. This section serves to co-operate with section ab when the effective length of that section is to be changed.

' The section de, which will be described before the section cd, is equal in length to an integral number of half wave lengths and, as is true of section he, does not transform the oscillations from tube T. This section serves to separate the antenna A from the plane mirror or reflector M. The area behind the reflector provides a region where mechanical adjustments can be made without causing disturbances in transmission or reception.

The section cd is equal in length to an odd number of quarter wave lengths, as

1A six for example. This section performs the function The mathematical method of computing the necessary characteristic impedance of the section physical dimensions of the section cdrequired to accomplish the above-mentioned match will now be given.

If we suppose that the section of the line ab has been adjusted so that the reactance component of the radiating element of the tube has been annulled, our problem reduces to the following simple case:

The amplitude of To make is a maximum, we difierentiate re 2;:

i i z+ $)2 F i l J+ r This gives the value of characteristic impedance of the quarter-wave section of the line cd in terms of R1, the resistance of the tubes generating element, and R2, the radiation resistance of the antenna, in order that maximum transfer of energy shall take place from the tube side to the antenna side of the system.

In order to facilitate the match when the above-indicated computations have shown the cd, severel methods are employed for varying the characteristic impedance of this section.

According to one method, the characteristic impedance of this's'ection can be readily altered by utilizing external cylindrical conductors of dinerent internal diameters. To change the external conductor of this section for one of a different diameter, the external conductor is made in two halves, as shown in Fig. 7A.

Accordingto another method, the characteristic impedance of this section can be changed by a simple translation. Referring to Fig. 10, the

handle 10 is attached to the outer conductor 12 which is provided with the various size bores or openings 17, 18 and 19. The movement of ,handle causes the conductor 12 to slide back and forth over the inner conductors 14 and 15. Conductor 13 passes through the conductors 14 and 15 and is held in proper position by the insulator 16. By moving the handle 10 back and forth, the proper adjustment is made between the conductors until the desired characteristic impedance of the sec,-

tion cd is obtained.

According to a further method, the characteristic impedance of the section cd may be varied in a continuous manner. The means for accomplishing this result willbe understood by reference to Fig. 11, in which the outer conductor 22 is provided with a handle 10 which, when moved, causes the conductor 22 to rotate back and forth around the axis 20. The hearings or rings 23 are provided for supporting the conductor 22 when it rotates. The conductor 13 is placed inside the conductor 22 and in eccentric relation to the inner surface of that conductor. It is to be noted that the wall of conductor 22-is of varying thickness. When the conductor 22 is rotated by the handlelO, the distance between its inner surface and the conductor 13 is continuously varied.

In the description and drawings, the sections ab and cd of the transmission line have been changed or adjusted by adjustments of the external conductor of the line. It is evident, howby adjusting or changing the inner conductor of the line or both conductors. It is believed that such other adjustments would be merely mechanical expedients and for this reason, and also to simplify the drawings and specification, any detailed description of them is omitted here.

Referring to Fig. 8, the tube is placed in a hut or building behind the parabolic reflector. A half wave length antenna A is placed at the focus of'the reflector. Although a half wave antenna is shown in the drawings, it is to be understood that antenna of other wave lengths may be employed, providing they are equal in length to integral multiples of a half wave length. The transmission line has been elongated at section de, but otherwise the transmission line is identical with that shown in Fig. 7. The line, where it enters therefle'ctor, is-held by an insulator, and on the antenna side of the reflector is held by at least three strings or cords (onlytwo of which are shown). It is to be understood that other means of rigidly supporting the line at the reflector may be used.

It is evident from the foregoing description that the tube, having been placed behind the reflector in order to avoid irregular radiation distribution, the difliculty arose that ordinary transmission lines, without considerable care and expense in their construction, did not give a satisfactory percentage of energy transference between the tube and antenna. A novel transmission line ity of sections, at least one section having a variable effective length for compensating for the reactance of the tube, and at least one other section having a variable characteristic impedance for matching the resistance of the tube side and the radiation resistance of the antenna. with this transmission line maximum transference of energy between the tube and the antenna is obtained, with a consequent increase in the inever, that the desired adjustments could be made was then designed. This line comprised a pluraltensity of the signals transmitted and received.

Although only single tube systems have been described, it should be understood that the principles developed above regarding transmission lines may be extended to systems utilizing several tubes, either one or several transmission lines heing used for coupling the tubes to the radiating I element.

What is claimed is: l

1. A transmission system for ultra-short waves, comprising a parabolic reflector, a tube located behind said reflector; a radiating element located at the focus of said reflector, and a sectionaltransmission line connecting said tube and said element, at least one section of said line having an axially adjustable conductor of varying crosssection for matching the resistance of the tube side to the radiation resistance of said element.

2. A transmission system for ultra-short waves, comprising a reflector, .a tube generating high frequency oscillations located behind said reflector, an antenna located at the focus of said reflecter, a transmission line having distributed but no lumped capacity and inductance and composed of concentric conductors joining said antenna and tube, the transmission line being divided into three portions: one to compensate for the tube reactance, one to match the resistance of the tube side to the radiation resistance of the antenna, and one to space the radiating antenna at a suitable distance from the reflector.

3. A transmission system for ultra-short waves, comprising a source of high frequency oscillations, a radiating element co-operating with a reflector interposed between said element and said source, a sectional transmission line, comprising a plurality of conductors concentric to one another, connecting said source and said element, and means for varying the radial spacing of the 115 conductors of a section of the line by a simple rotary movement of a section of one conductor.

4. A transmission system for ultra-short waves, comprising a source of high frequency oscillations, a radiating element -co--operating with a re- 120 flector interposed between said element and said source, a sectional transmission line, comprising a plurality of conductors concentric to one another, connecting said source and said element,

and means for continuously varying the radial spacing of the conductors of a section of the line by a simple rotary movement of a section of one conductor.

5. A transmission system for ultra-short waves, comprising a source of high frequency oscilla- 13 tions, a radiating element co-operating with a reflector interposed between said element and said source, a sectional transmission line, comprising a plurality of conductors, connecting said source with said element, one of said conductors being placed eccentrically with respect to the inner sur face of the other conductor, and means whereby the rotation of a section of one conductor changes the radio spacing of the conductorsof said section of the line.

8. A transmission system for ultra-short waves, comprising a parabolic reflector, a source of high frequency oscillations located behind said reflector, and a transmission line connecting said source and said element for adjusting the resistance of said source to the radiation resistance of said element and for annulling the reactance of said source, said line comprising a plurality of sections, at least one of said sections having the conductors thereof spatially variable and at least 'rality of sections, at least one of said sections having a variable characteristic impedance and at least another of said sections having a variable effective length.

' 8. A transmission system for ultra-short waves, comprising a source of high frequency oscillations, a radiating element, a transmission line, comprising a pair of concentric conductors, connecting said source and said element, and means for tuning said transmission line comprising at least one section of line having a third concentric conductor between the other two, said third conductor connecting two portions of one conductor;

means for sliding said third conductor longitudinally to alter the efiective length of said connected portions, and also comprising at least another section of line composed of conductors which are spatially variable. I

9. A transmission system for ultra-short waves, comprising a source of high frequency oscillamemes tions, a radiating element, a tr wut; on line, comprising a pair of concentric conductors, conmeeting said source and said element, and means for tuning said transmission line comprising at least one section of line having a third concentric conductor between the other two, said third conductor connecting two portions of one conductor, means for sliding said third conductor longitudinally to alter the eiiective length of said connected portions, and also comprising at least another section of line having a variable characteristic impedance.

10. A transmission system tor ultra-short waves comprising a parabolic reflector, a tube located behind said reflector, a radiating element located at the focus of said reflector, a sectional transmission line connecting said tube and said element and comprising one section having two con ductors, one being positioned within the other, and'means for varying the distance between said conductors;

11. A transmission system for ultra-short waves

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