US1987780A - Antenna system - Google Patents

Description

M. LATOUR ANTENNA SYSTEM Filed July 30, 1929 2 Sheets-Sheet l INVENTOR MARIUS LATOUR BY fim DMMM waiaflm,

ATTORNEYS ANTENNA SYSTEM Filed July 50, 1923 2 Sheets-511961, 2

RNVENTOR MARIUS LATOUR ATTORNEY Patented Jan. 15, 1935 UNITED STATES;

ssmse PATENT OFFICE ANTENNA SYSTEM.

Marius liatour, San Sebastian; Spain Application July 30, 1929, Serial No. 382,203 In France'August: 27, 1928 2' Claims.

' short wave systems for radio transmission and reception.

Short wave directive antenna arrays have been devised comprising an aerial screen arranged in the form of a Greek fretwork consisting of a continuous conductor bent in such fashion as to comprise periodically recurring vertical and horizontal sections developed in one and the same plane. The object of such antenna arrays as have previously been disclosed, is to radiate the maximum energy in a direction perpendicular to the plane of the system.

According toone object of the present invention, the employment of these fretwork antenna screens is generalizedfor.radiating the maximum energy in any desired direction relative to the plane of the antenna fretwork or screen.

A further object of the inventionis to combine a plurality of these fretwork screens in such manner asv to increase to a desired extent the effective radiating or receiving surface of the antenna.

The invention makes possible the combination and connection of a plurality of fretwork screensin such fashion as to present a single pair of adjacent terminals for connection toan oscillator,

whereby the entire antenna system may be suitably energized from a single. source; or conversely to provide a single pair of adjacent terminals for connection to a detector element in aradio receiver whereby waves impinging upon the antenna system produce additive effects. in such detector.

It is a further object of the inventionb'y employing a plurality of aerial 'fretworks ,situatedin parallel planes, to suitably combine their efiects in such manner that the arrangement corresponds, as an installation, to that ofa screen of aerials arranged perpendicular to the direction of the wave. propagation and having reflector screens arranged parallel to such direction.

By means of this invention, it is possible to combine a plurality of such antenna screens so as to obtain maximum radiation in a plurality of preselected directions, or if desired, uniform radiation in all directions.

It is, moreover, possible to combine the fretwork.

aerials of the present invention with those wh'erein the radiation is perpendicular to the plane of the aerial such as have been described by Rene Mesny. By such a combination it is possible to obtain a great many different types of'directional antenna systems; two specific forms of, directional antenna systems being described in my French Patent No. 579,224 of June 5, 1923, and French patent of addition No. 28,333 of June 13, 1923.

Referring to the drawings: Figure 1 shows an elementary antenna system of the type de: ribed herein consisting of a single continuous conductor developed into a screen or fretwork consisting of repetitions of the Greek letter 5'.

Figure 2 shows an antenna system similar to Figure 1 but differently proportioned relative toithe wavelength, to produce maximum radia-- tion-in the plane-of the antenna.

Figures 3 and4 show antenna arrays in accordancegwith modified forms of Figure 2, and being energized differently from the'ant'enna of Figure 2; ineach case, however, producing maximum radiation in the plane of the antenna.

Figure 5 shows an arrangement combining a plurality of antenna of' the type indicated inthe type indicated in Figure 4 in such.manner as to obtain maximum radiation in the plane of the antenna.

Figure 7 shows an arrangement combining a dimensions consisting of a plurality of rows of antenna arranged to give maximum radiation in a direction parallel to the antenna planes.

Figure 8 shows a modification whereby a single continuous conductor may be shaped in such manner as to produce the same type of radiation characteristic as is obtained with a plurality of antennae arranged in accordance with Figure 7.

Figure 9 shows a modification of Figures 2 to 4 inclusive, whereby by the interposition of a plurality of suitable inductances properly located at various points along the antenna conductor, the radiating surface of the. antenna system may be increased for a given wavelength as compared to the arrangements of'Figures 2 to 4 inclusive.

Figure 10 shows a modification .of Figure 5 utilizing suitably placed inductances for the purpose of increasing the radiating surface of the antenna system in the same manner as was indicated in Figure 9.

Figure 11 shows a loop antenna in accordance with the present inventionsuitably dimensioned and energized to produce improved directional radiation or reception.

12' shows an arrangement consisting of a plurality of distinct antenna systems situated in a common plane and so positioned and adapted to be energized in such relative phase relations plurality of elementary antennascreens-in three direction of maximum radiation to the dimensions of the antenna screen or fretwork is as follows:

where, h=the height of the vertical portions of the antenna as indicated on Figure 1,

x=their spacing distance horizontally,

a=the angle at which the direction of maximum radiation is inclined with reference to the plane of the screen,

\=the wavelength radiated, and

n=any integral number, and which can be zero.

In particular, if

and the antenna is energized by a generator G or G connected from ground thereto at the midpoint of a horizontal strand, it is obvious that the direction of maximum radiation will be perpendicular to the plane of the antenna since the currents in the vertical strands are all in the same direction as shown in Fig. 1, and hence have the effect of a sheet of current directed alternately upward and downward in the plane of the antenna. The currents in the horizontal strands being oppositely directed, annul one another. The truth of the above statements is demonstrated mathematically with Equation (1) by placing a= and 272:0. An antenna constructed in accordance with these relations has been devised by Mesny, as above referred to.

Again, with reference to Equation (1), if the assumption is made that a=n=0, two interesting special cases are obtained. In the first place, if the antenna is so dimensioned that then :1: becomes In the second place, if we make then a: may be zero or any integral number of half wave lengths. It will be noted from the above relations, that an antenna arranged to operate according to the first relation utilizing a wavelength equal to 4h can be employed to operate in accordance with the second relation using a wavelength equal to 2h. In each case, of course, the direction of maximum radiation will be in the plane of the antenna, since by hypothesis, it was assumed that 0:0.

It was noted above in connection with the second arrangement mentioned, that w could be any integral number of half wave lengths. In practice it is convenient so to construct the antenna for this case that puted directly from Equation (1) having once determined upon the wavelength to be utilized. It is obvious, of course, that everything that has been stated above regarding transmission, applies equally to reception.

Figure 2 shows an antenna constructed in accordance with the assumption first above-mentioned, wherein If such an antenna be energized at the midpoint of one of the vertical strands (as indicated by the letter G representing an oscillator connected from ground to the midpoint of a vertical strand), then the antenna will be so energized as to produce maximum radiation in the direction indicated by the double arrow :1 lying in the plane of the antenna. The reason for this is that the successive vertical strands are energized at each instance by the source G, in such phase relations that waves are continuously propagated from the oscillator in the direction (1 by the successive vertical strands. Thus, for the first three full vertical strands counting from the left, the currents are directed upward. In the fourth strand the resultant current is zero; in the next three vertical strands the currents are all directed downward; and in the next strand the current is zero,

and so on. Moreover, the relative phase relations are such that the current magnitudes in the successive vertical strands are at each instant proportional to the intensities at such points of the electromagnetic waves being radiated.

It may here be noted that in general the generator or oscillator may be connected at any point of the antenna system such as G where either the heads or the tails of current-arrows meet.

The currents in the horizontal strands produce no propagation in a direction perpendicular to d in the plane of the antenna, since, for example, the current in strand 6 is 90 out of phase with that in strand 7, and is separated spacially therefrom by a distance equivalent to a phase difference of 90. The result is that waves simultaneously propagated from the upper and lower horizontal strands will arrive at a given point in phase opposition and hence will annul each other.

Similarly, the radiations in the direction perpendicular to the plane of the antenna will be small since the effect at any point outside the plane due, for example, to the upward currents in the first, second and third vertical strands will be annulled by the corresponding effect due to the downward currents in the fifth, sixth and seventh vertical strands, respectively, and so on. And again, the eifects produced by currents in the upper horizontal strands will be annulled by the opposite effects due to currents in the lower horizontal strands.

Referring to Figure 3, if the horizontal sections :17, each are made equal to and the vertical sections and the antenna again energized by oscillator G, a point where the arrows oppose, the propagation will again be in the direction :1, but in this case, the wavelength of the propagated wave will cover only four successive distances 3: instead of eight as was the case with Figure 2.

7, clusive.

as-follows:

It is obvious that by applyingtothe; antenna-of- Figure 4, a wavelength-twice that. whichgivesradiation in the direction cl; namely, one wherein .4h, a maximum.=radiation in; adirectionperpendicular to the plane of .theaerial; will result. It would therefore bepossible-byemployingtwo similar antennae, like that shown inFigure. 4,. placed alongtwo perpendicular planes (sothatthe portions herein referred to as the horizontal portions are perpendicular) to transmit with two wavelengths, namely- )\=2h;--and \=4h, along the selecteddirection ineach plane or perpen dicular to each, as desired, Otherwise, it would;

take four transverse-radiationaerials-to accomplishthe. same result.

It will be notedin each of the figures shown that the-cornersrbetween the vertical and hori+ zontal sections are rounded off This; is a done inorder to lessen the eifects-ofthe variation'of, electric constants of theconductor'due to;dis-- continuities at such points, and :hence; to t-mmimize reflection of, the: energizing current" and The reflection is re-. duced in accordancewith'the degree of 'rounding" off.

Figure'5 representsa combination of two aerial other undesirable effects.

screens each of which is similarto that OfFigure generator- G so that the entire antenna I system maybe properly energized from a common generatorsource, and furthermore; sothat no difficulsl ties may be encountered dueto a ground return.

or the like, such as wouldnormally be the case with thefretwork screenszof. Figuresl to incorresponding vertical strands of the respective;

radiating surface ofthat of-Figure 4. Itiseasily seen that. the radiations from any. two corresponding horizontalstrands of. the respective,

antennae are. annulled, since thecurrentsinfthe respective strands are 180 out ofvphasaelectrically, and are separated by a distance corresponding to or 360 electricalldegrees phase displacement. The result is that currents propagated to any point from the. two strandsfarriveatsuchi point in phase opposition to each other, and hence produce zero resultant effect.

Figure 6 represents a combination of two aerials each similar to that of Figure fand between the upper horizontal strands of the other aerial. Electrically, this antenna arrangement is the same as that of Figure 5, except for Itwill be noted. that the currents in the r ground return to; the generator already: re:- ferred to. The:radiation from this arrangement is in the direction d in the plane of the antenna, the radiating area being double that of Figure 4. The radiations from corresponding horizontal strands; of: the respective aerialszannul. one anothensince, the currents therein are in like phase relation. and are: separated, spacially by 180. Waves: propagated therefrom to a given point thus-arrive in phase opposition.

Figure 7 illustrates two combinations, each of them similaix to that of: Figure. 6,: and mounted. intwo parallelplanes one behindthe other and distant one-half wavelength from each other; one of the combinations is finely traced and the other heavily, for, the ipurpose-gof identification.

The antenna arrangement of Figure '7 produces maximum radiation in the direction 11 which is'parallel'to the planes of the individual aerialsz The radiation surface for the arrangement ofiEigure "ii is; of -course, double that of Figure 6. The;- radiation oftwo horizontal strands: such as 3 and 4-along a line perpendicular to these strands and to the plane of the aerials, is annulled, because the currents follow then-same direction and are distant from each other one-half of the wavelength. Currents fromthe: two: strands thus. arrive atanypoint in phase opposition.

Anyof the systems developed in a single plane, as those-illustrated in Figures 2. to 6, inclusive, maysbe combined. withsimilar systems after the manner of Figure 7, arranged in the-=formof parallel. planes,v one behind the other.

Inorder to obtain maximum radiation only towards one side or one way: in the" direction of the planes-cf the antennae, two identical -sepa-- rate systems of antennae might be provided which could stand on; the same line one after the. other in the-direction of: propagation, the centers of' the twor systems beingaat a distance-of The; two systems: shouldi then be energized" by currents displaced: by x In fact only one systemgoi antenna;mightv be energized in which case-the, other system .willtact as-a reflector of.electromagneticwaves. In this connectiondt shouldbe pointed out; that; any system of antennae may act simultaneously. as a, source; of radiation as well as a: reiiectcnfor waves impingingupon the same and. propagated from the other antenna.

Fig. 12 shows'graphically the manner of positioningtwo distinct. antenna systems for pro--.

ducing' maximumradiationin a: direction. to.

the: right only orzhto the left only in:. the plane ofqtlie drawingsl.

between :adjacent .cornersof the :upper. and flower:

screens.

betweenradjacent corners of the upper. and lower screens. The midpoints between systems Auand B are separated by the distance mounted in the same plane onedirectlyabove" the other, so that the lower horizontal strandsof one aerial are on linewith andare interposed referred to-abovewheren is=any integral number, including zero.

System A: is energized: atits, midpoint by algenerator G1 connected asshown;

System B: is similarly. energized. by a; generator G2 connected at:the midpoint thereof Generators G1- and: G2 fare s operated that the currentsgflow-ing in system-1m 1 are displaced in phase relative to the currents flowing in system B by the angle With these conditions fulfilled, the maximum radiation will be to the right only or to the left only in the drawing depending upon the value of n. There is no restriction as to the proportioning of the individual screens of system A and B beyond the fact that all should be identical with one another and the horizontal and vertical sections of the individual screens should satisfy the equation h+2x=(2n+1)%- (3) Figure 8 shows an arrangement for producing the radiation characteristics of Figure 7 by utilizing a single conductor bent in three-dimensional form, as indicated on the drawing. This antenna will, of course, produce maximum radiation in the direction (1, since currents in corresponding vertical strands such as 1, 2, and 3, are all in the same direction and are reversed in phase as compared to the currents in the next succeeding vertical strands, such as 6, 7 and 8. The currents in the perpendicular strands produce no effect in the direction d, since the currents in a pair of such strands such as 4 and 5, are reversed in phase and will thus arrive at a given point in the direction (1 in phase opposition.

It will be noted with reference to Figure '7 that the currents in each of the vertical strands situated in a given plane perpendicular to those of the individual fretworks, such, for example, as the vertical strands 5 to 8, inclusive, are all in like phase relation and hence directed the same. The currents in any such plane thus amount in effect to a sheet of current flowing in the same direction at all points of the plane and hence causing the propagation of a wave front in a direction perpendicular to such plane, such as direction d, which is the direction of maximum radiation. The individual fretworks or screens. on the other hand, are arranged parallel to the direction of maximum radiation, and hence act as reflector screens adapted toreflect substantially in the direction of radiation, waves propagated at an angle to such direction. For example, consider a wave propagated from the antenna containing the element 5 in the direction of the antenna containing the element 6. This wave, upon reaching the antenna 6, provided it impinges upon the same at an angle less than the critical angle, will be reflected by the antenna 6 back towards the antenna 5. Upon impinging upon antenna 5 it will again be reflected towards 6, and so on indefinitely, with the net result that such a wave will be directed substantially in the general direction of propagation d. It will thus be seen that the antennae located in a given plane act as a reflecting screen for waves impinging upon the same and propagated from antennae located in other planes, the reflection in each case being in such direction as to cause the reflected wave to be propagated substantially in the direction of maximum radiation (1.

The same reasoning, of course, applies to the antenna of Figure 8. Here again, the currents in all of the vertical strands located in a given plane perpendicular to the direction d, are in the same direction as, for example, currents in the strands 6, 7 and 8, and hence, the efiect is that of a sheet of current flowing in the same direction at all points in such a plane, thereby causing a wave to be propagated in a direction perpendicular to such plane, such as direction at. The ver tical strands located in one plane parallel to the direction of propagation, such as 2 and '7, act as a reflector screen for waves impinging upon the same and propagated from the vertical strands located in another plane parallel to the direction of propagation, such as strands 1 and 8.

Antenna systems, such as those of Figures '7 and 8 are, therefore, seen to constitute very effective directive antenna arrays, since substantially all of the energy radiated in any direction from a given elementary vertical section is caused to be propagated in the direction of maximum radiation. As was pointed out above, the waves which are propagated from one reflector screen and impinge upon the next succeeding reflector screen at an angle greater than the critical angle, and hence pass thru the same, are neutralized by other waves radiated from such second screen which are propagated therefrom 180 out of phase with the impinging waves.

Figure 9 shows a modification of Figure 3 arranged for the purpose of increasing the radiating surface of the antenna for a given wavelength. Since each vertical strand covers a distance of three-halves of a wavelength, ordinarily the current would flow in opposite directions in diiferent portions of the same vertical strand, and hence, the radiation would be correspondingly reduced. In order to prevent this, the inductances such as 4 and 5, are interposed at each one-half wavelength and are constructed to absorb one-half of a wavelength, being practicaly nonradiating. The result is that the currents in the vertical portions 1, 2 and 3, are all in the same direction, the reversed half-waves of current being dissipated in the coils, and hence, producing no effect upon radiation. It will thus be seen that by this process the efiective height of the aerial may be increased to any extent, and is not limited as is the case of the antenna of Figure 4.

Figure 10 shows an arrangement similar to that of Figure 5, but combining the ideas disclosed in Figure 9 by utilizing the inductances to absorb the reversed portions of the currents. The intermediate feeding as by a generator at G, can, of course, be utilized for Figure 10 in the same manner as was the case for Figure 5. Intermediate feeding in the case of Figure 10 results in increasing the efiective height of the antenna by one-half wavelength as compared to the arrangement of Figure 9, while at the same time utilizing the same number of coils in each vertical section as is used in the system of Figure 9.

Inductances of suitable values, like those of Figures 9 and 10, may be inserted in the horizontal strands of systems like those of Figures 3, 4 and 5, whereby the height of the aerial can bereduced below while maintaining the spacing at Figure 11 represents a modification consisting of an aerial arranged in the form of a loop antenna, but having the vertical and horizontal portions each dimensioned according to segments, each of a length it, which comprises applying to said antenna electrical waves of length A greater than 2h and less than 4h, whereby maximum radiation occurs at an angle inclined to said antenna plane.

2. The method of operating a radio system including adirectional antenna of sinuous form consisting of mutually perpendicular coplanar segments of lengths h and a: respectively, which comprises, applying to said antenna electrical waves 10 of length A less than 2(h+2:n) and greater than 2(h+a:), whereby maximum radiation occurs at an angle inclined to said antenna plane. 1

MARIUS LATOUR.

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