US1874966A - Aerial system and feeding system therefor - Google Patents

Description

Aug. 30, 1932. R E 1,874,966

AERIAL SYSTEM AND FEEDING SYSTEM THEREFOR Filed March 24, 1927 INVENTOR ERNEST GREEN TORNEY Patented Aug. 30, 1932 nnnnszr GREEN, or

AERIAL SYSTEM ANDFEVEDINGSYS'TEM rrrnnnron Application and 1mm, 1927, Serial No, 177,979, and in Great Britain a rirao, 1926.

This invention relates to aerial systems, and, feeding systems therefor, and more particularly to aerial'systems for use in direc-i tional radio telegraphy andtelephony.

In general, aerial systems for use in directional radio telegraphy and telephony have dimensions of the order of several wave lengths, and are fed with high frequency at a number of points throughout their extent by means of cables.

The object of the present invention is to provide a feeding system for use with such an aerial system in which reflection along the cables shall be reduced to a minimum.. In the simplest type of aerial system, comprising a single aerial fed through an aerial transformer and length of uniform cable from a source of high frequency energy, reflections are substantially eliminated when the tune of the aerial and the coupling of the trans former are so adjusted that the effective load at the aerial end of the cable is a resistance numerically equal to the square root of the quotient obtainedby dividing the effective inductance by the effective capacity. Hereafter the said resistance, which is, of course, equal to the surge impedance, will be designated by the symbol R0.

With a more extended aerial system, how- 0 ever, the minimizing or elimination of reflections becomes more diflicult. For example, consider a known case of an aerial system comprising four aerials, each fed through an aerial transformer, the primaries of the said aerial transformers being connected together in pairs by two lengths of twin aerial cables which are connected together at their midpoints by a length of intermediate twin -cable which in turn is fed at its mid-point by a transmitter twin cable, leading to the source of high frequency energy. If, in such an installation, the aerial loads be adjusted as set out above, reflections will still be set up at the points of juncture, giving rise to strong stationary waves in the cables.

The present invention provides a method wherebysuch stationary waves may be substantially eliminated in the transmitter cable, and reduced in the intermediate and aerial cables.

In a cable in which the terminal 'load' is not a resistance equal to the surgetimpedancel. R0, stationary waves are, set up, but at points in the cable .onefquarter' .wave length apart, voltage and current are in phase, that is to); say, at those points the efiectof the load and cable'to such a point is thatof a pure resistance. Neglecting attenuation, if at any ATENT? oFF lcs Q Brannon, oNnon,-n1vGLAND, ASSIGNOR "ro RADIo'rooRPonAmIon OFAMERICA, A conronnrron OEDELAWARE such point the value of resistance-isK Re, i

then at the next such-point will be %Bo,

at the next K R0, and SojonjiFor example, in the extended aerial-system already re-@ ferred to, if the aerial loads are adjusted so '1 i that there are no reflectionsin the aerial cables, the load on the intermediatecablesat their junctionswith the aerial cables V-will be Rog hence, stationary Waves will be,

set up in the'intermediate cables." I

.According to dlhlSjlIlVGIltllOIl those cables which connect points of juncture and in which there is liabilityforlstationary waves tobe. set up the manner hereinbefore described) are made an odd number of'quarter 1 wave lengths long, so thatthe effective impedance of each such cable at their own point a of juncture v is substantially aresistance equal to the number of such cables times Bo.- u a r In-this way the impedance of those cables which connect points of, juncture, being ,in'

parallel at their own point of juncture, will give rise to an, effective load equal to that of a resistance Be, "on the nextcable towards thetransmitter at the point of'juncturetherewith, i 1

n will be sees that f that be an as;

number of junctions between the transmitter j and any aerial of anaerial, system, anar-t rangement as above described will eliminate a 'stationary waves between the transmitter and the nearest; junction. If, however, there be an odd numberof junctions, it will be necessary either to provide a transformer atthe said junction oradjust the aerial loads I 5.1% in the system described) and lengths of aerial cablesto fgive therequiredeffectiveimpedance values. (2R0 inthecase of the 'exa tended. aerial system described) at ofjunctionsf 4 The invention is illustrated in the accompanying diagrammatic drawing, which shows a feeder system adapted to supply energy to an aerial system comprising four aerials.

Referring to the drawing, A1, A2, A3 and A4 are aerials fed through cable sections 1, 2, 8, 4, 5, 6, 7, by way of junctions T1, T2 and T3. It will be seen that if the aerial loads are correctly adjusted so that there will be no stationary waves in the sections 1, 2, 3, 4E, thetwo sections 1' and- 2, in parallel at the junction T1, constitute a load v A R0 upon the section 5. Similarly the sections 3, 4, in parallel constitute a load Roupon the section 6. It follows, therefore, that stationary waves will be set up in thesections 5 and'6; In accordance with the present invention, the sections 5 and 6 are made each an odd number of quar-' ter wave lengths long,'so that the effective impedance of each at their junction T3 is substantially that of apure resistance 2R0.

' with by definite transforming devices at the said junctions. V

The invention is equallyapplicable to the reception as to the transmissionof wireless tele raphy' and telephony; j

I aving thus described my invention, what Iclaimis: 7

1. A feeder or the like for feeding high frequency energy to a pluralityof antennae comprising a transmitter twin cable, an intermediate twin cable, and a pair of twin aerial cables coupled at their ends to said antennae through a couplingwhich impresses a load on said' aerial cables equal'to their surge im: pedance' whereby standing waves are eliminatedin said'twin aerial cables, said inter-.

mediate twin cables being connected atits ends to the mid-points of each of said twin aerial cables and at its mid-point to said transmitter twin cable and being an odd number of quarter wave lengths long in each branch whereby standing waves are eliminated in said transmitter, twin cable.

2. An energy transfer system between a high frequency source and a plurality of high frequency circuits comprising a path from said source, a pair of paths connected to the first mentioned path,said pair of paths each having. a'lengt h equal to an odd number of quarter wave lengths of the energy being transferred, and means electrically connect ing said pair of paths to said plurality-of high frequency circuits, said means impressing a load on saidpair of paths which is equal to one-half the surge impedance of said paths.

3. An energy transfer system between a high frequency source and a plurality of high frequency circuits comprising a path from said source, a plurality of pathsconnected to the end of said path, each of said plurality of paths having an; effectivelength equal to a quarter wavelength of the energy being transferred, and means electrically connectingsaid'pluralityof paths to said high frequency circuits, said means impressing loads .on the ends of said plurality of'paths of such values that their reciprocals will combine at the end of the first mentioned path to form vanimpedance equal to the surge impedance of said first mentioned path.

ERNEST REEN; R

Dr: La)

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