US2479337A - Antenna system - Google Patents

Description

Aug. 16, 1949. G. w. FYLEFg 2,479,331

' ANTENNA SYSTEM Filed Oct. 16, 1945 2 Sheets-Sheet 1 Invent or George W. Fyl

H is Attorney.

Aug. 16 1949. w FYLER 2,479,337

I ANTENNA SYSTEM Filed Oct. 16, 1945 2 Sheets-Sheet 2 Invehtor:

hzm 45m H is Attorn ey.

Patented Aug. 16, 1949 George W. QFyIerJStratfond, Conn .as's ignor .to General ,Electric Company, a corporation of New York Application center '16, 1945, S er i'al naqesas'ia My present invention *relates 'to' high frequency antenna systems, and particularly to high frequency Tantenna systems 1 designed to provide substantiallyfcircular radiation patterns. This application isc a continuation "in part of my U. S. Patent-No; 2,405,123, granted August 6,4946. .In broadcasting radio programs within the higher frequency channels utilized for frequency modulation and television broadcasts, it is generally desirable to :distribute the energy radiated from the transmitting antenna as uniformly as possible all lioiizontardirections. At the same time, it is desirable to concentrate the radiated energy at lowrang-les in'the verticalgplane. In other Words, iorimostefleotive service, the radiatnag-system should h'avea highrdegree of vertical directivity and the horizontal field-strength patterm should be *as nearly circtilar' as possible.

Accordingly, it is an'ob'ilect of my invention to provide an improved high, frequency antenna which possesses these and nth'er desirable electrical characteristics.

In general, simple two-terminal antennas, such as dipoles theretofore commonly used, have nonuniform radiation characteristics. It has heretofore been customary to resort; to compound antenna arrangements in order to secure a reasonably uniform horizontal wave pattern with horizontal polarization. It isanother object of my invention to provide an improved and simplified compound antenna structure which is capable of producing a substantially uniform radiation patten and which is relatively'economical to build and easy to adjust.

Still another object of my invention is to provide a new and improved antenna system which has only two connection terminals and which nevertheless provides a substantially circular radiation pattern and the radiation of which is concehtrated substantially in the horizontal plane.

The features of 'n'iy. invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself; both as to its organization and manner of operation; to-

gether with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig; 1 is a perspective view of an antenna systerii em: bodying the principles of my invention; Fig. 2 shows vectorially the relationship of the current and voltage present onthe antenna of Fig. 1;

Figst 3,- and- 5 show modifications of the system" 1 2 claims. (crash-a3) V i v.2 illustrating characteristics of antennasysteins of the type illustrated 'in Fig. 5; and Fig. 9shows another embodiment of my invention.

As is well -tinders't'o'c ic'l in the art, a properly terminated transmission line does not have any standing waves. In Figs- 1 and 2 there iss'hown an. antenna system 'in which a transmission line sectionis utilized as aradi'ator', the 'line section being formed into 'a. circular loop and the ends coupled to a suitable source bf signal voltage. Such "an antenna has substantially uniform current and hence a substantially circular radiation pattern in. the plane of the loop, provided proper adjustments have been made of the termination or the line and its coupling to a soiircebf high frequency waves.

In Fig. 1 there is shown such a transmission line antenna or radiatingtransmission line. The antenna comprises a substantially closed circular loop M formed from electrically conductive material of any desired cross-sectional shape. For example, the loop may be asuitably formed pipe disposedwina circular configuration. The loop is coaxially disposed around a suitable electrically conductive member such as a cylindrical grounded mast 'H to. form therewith a short section of transmission line. l

The loop I 0 is suitably supported from the mast by means of a supporting member I 2 of insulating material, suitably connectedat its respective ends to, the loop and to the mast and of such length that the loop and mast are spaced apart approximately a quarter of a wavelength, or less. Thus there is provided a transmission line conductor and a grounded mast, the mast serving as a reflect'or for the loop.

There is illustrated inFigs. 1 and 2 means for energizing a system in which the length of the loop lilis an integral number of full wave lengths; There is provided a, transformer [3, having a primary L4 and ya secondary I5; carried by the mast H. Any suitable transmissidri line l6 may be utilized to cited) the transfer of eneigy between the. primary. l4 and a suitable source of signal voltage which may comprise the high frequency radio apparatus or transmitter represented the. box l1. One. end of the secondary I 5 is suitably connected' to the mast n and" th other terminal of the secondary is connected to the mast through a variable condenser l8. Thus winding [5 and condenser i8 constitute a tuned" circuitwhich enables proper tenet transmissionnne rs; In installations whr wide and operatio'r'i desired; this tuned circuit and the anten'riasiiomdnave aibw Q: Iii s'ii'ch' a sysina'ti'on of tire;

tem, since the radiator operates as a transmission line rather than as a resonant dipole, no sharp resonance effects are present in the antenna, and the system exhibits relatively broad frequency band width characteristics.

The ends of the loop ID are connected to suitable points on the coil or winding 15 by means of suitable conductors l9 extending between the ends of the loop and the winding through a suitable opening IS in the mast.

In Fig. 2 there is shown the Vector currents flowing in the antenna ID of Fig. 1. The arrow heads on the circle IE) represent the directions of current flow within the loop and the arrows pointing inwardly from the circle I!) represent the voltage phase relationships at the indicated points. The loop I is energized from coil I by means of conductors l9 connected to desired taps on winding [5. With this arrangement there exists a difference of voltage across the ends of the and, at diametrically opposite points of the loop, f

are 180 out of phase and may be represented by vectors pointing in opposite directions. In eifect, therefore, the currents are in phase at opposite points of the loop H], in that these currents produce additive radiation fields along the axis of the loop, as well as radiation in all horizontal directions.

In Fig. 3 there is depicted schematically an arrangement which enables the application of the above principles to a loop having an electrical length equal to an odd number of half waves. A balanced input circuit to the loop is shown. The ends of the transmission line I6 are connected directly to the ends of the loop 20, a suitable condenser being used properly to terminate the line in conjunction with a short length of line joining the antenna 20 and the transmission line H5. The vector voltage and current relationships are shown by means of arrows. The phase of the loop current and voltage changes uniformly and progressively throughout the length of the transmission line antenna and the vectors make a half revolution in approximately one half wave length of line. The amplitude does not change appreciably, however, and, as long as the spacing between the loop and mast 2| is not great enough to introduce substantial radiation resistance and, hence, attenuation, a uniform substantially circular radiation pattern results.

In Fig. 4 l. have shown a modification of the antenna structure of Fig. 1, in which a pair of substantially circular loop elements ID, ID each have an electrical length equal to an integral number of full wave lengths at the operating frequency of the antenna and, spaced from the conductive mast H by a distance equal approximately to a quarter wave length or less, are spaced apart vertically by a distance 7\/2 equal to a half wave length. Positioned below the lower element ID by a distance M4 equal to a quarter wave length is a conductive reflector plate H. The ends of loop H] are connected to a source of signal I! by means of conductors l9, l6 and. the ends of loop ID are connected to the source by means of conductors l9, H5. The length of connection from the source to loop I0 is made half a wave length longer than the connection to loop l0 so that these coaxial loops carry currents which areopposite in phase. Since the currents in the loops are 180 out of phase, the horizonta radiation of the loops is substantially completely cancelled, while their vertical radiations are additive to give a concentrated highly directive beam of radiation. By means of the reflector l I, this vertical radiation is confined to a single direction, namely, upwardly along the axis of the loops. Normal to the plane of the loop, therefore, is a concentrated beam of radiation. Such an antenna is relatively small and simple in structure and is particularly useful where concentrated radiation in a small area is desired, for example, for better illumination of a parabolic reflector, or for use for diathermy and therapeutic work. Any larger even number of loops spaced apart axially by a distance equal to a half wave length with adjacent loops energized in opposite phase may be used, of course, to obtain a desired strength of radiation beam.

Fig. 5 shows the system of Fig. 3 with the addition of a driven substantially circular director 22 coaxially disposed and outwardly spaced 2. fraction of a wave length from the loop 20 which in turn is spaced approximately a quarter of a wave length with respect to mast 2| by which additional vertical directivity is achieved. With this arrangement a suitable phase delay line or matching section, indicated by the numeral 23, is required.

Still more vertical directivity can be obtained by using stacked elements with half wave vertical spacing and excited in-phase.

In Fig. 6 there is shown a modification of my antenna system which provides substantially uniform current therein and, consequently, a substantially circular radiation pattern. It is well known that a linear antenna which is actually one-half wave long at the operating frequency has a current distribution which is essentially sinusoidal, the current being maximum at its mid-point and zero at its ends. If the antenna is less than one-half wave long and capacity is added between the ends of the antenna loop in an amount such that the effective electrical length of the entire system is equal to one-half wave, the current at the free ends of the antenna is not zero, but has some finite value and the current distribution is more nearly uniform.

Accordingly, in Fig. 6, the loop or radiator 30 disposed in a substantially closed, peripherally incomplete loop constitutes a coiled up dipole and preferably has either a length of substantially less than one-half wave or a nearly uniform current obtained as discussed in conjunction with the description of Fig. 2. The electrical length may be much greater than the actual length because of the stray and, where desired, added capacity 3! between the ends of the loop. If the actual length is much less than one-half wave even when the stray capacity is considered, the free ends of the loop may be terminated in elements forming a condenser 3| of substantial capacity to provide a transmission line radiator of desired length.

In order to provide the desired capacity between the ends of the loop, blocks or plates 32 may be secured, as by welding, to the ends of the pipe and U-shaped plates 33 fitted over the opposing faces of the blocks. In order to provide an adjustable condenser, one or both of the plates 33 may be provided with slots (not shown) or other suitable openings registering with screws threaded into the blocks 32. Of course, any other desired means may be employed for varying or adjusting the effective capacity.

A small loop does not radiate to any substantial 5 coerce is a vertical eirecti ez-y e ieee be ent ssues an e ree eris and in emcee theme- T .eere eeieq iesia e. iihich the numeral ieei'eaie e ve tical-litres... Ratta Qt e. icon-it use to obta n a reatereeeree li er-coa sitcomts with this t me Q antenna the e be me ited a ubstantiall c cular i5 aced cctwe sl item. the 1.9 it ant com mg a nlere i r o el men s es bo ine ca b e d a nt nd- The rec or s su e ms con tri a ly arran ed w the ic n n d s ersa n u tantial y h sam lane- The re t s p ced ae r i q the 901 a sis.- tance'bf t o f T 6 s /2 er a r i e il ap ximat l A, we e: he is t r the aso ha e a enna s stem.-

t me her-myif th spacin is too see and lit le. an i i r ct -i s bt ned if ee. is oo reat T eia h of th tor eme ts; .6 sh uld b m w a s hee 1/2 ve e th so es. to i ein at l unif m. cur en di tr bution andto permit correct tuning. Accolxlingly, the spacing from the loop. and the length ortl re direcel n ar n er-r lated.

a e or at nsmi si n lin or may be uti lized to, efifect transier of energy between he i r ue a io appa atus. r t n -n t: n p s nt by th box stra the l op- The above ribe s stem has vertica d n e vi r Pat n a ere e o by the lo es so in Fig. 6.

In Fig-,7 there is shown another modification of my antenna havingt emission line charace s e a d t e r iai r which s l en: fi d. sub a ally n. h horizo tal man there being very little radiation in the direction transw verse om s-p s the r diat r he an there shown comprises theloops w 4:}; whiphsure; round the mast ill. Tneloops H}, 4.1 are relativelyclosely spaced with respect to each other and'the. 1 t s, e r m e mas i by a distance of the. order or .25. to .3 wavelengthat-tho operat: i frequency f, t stem T homes. to and. Iii-maybe supported from the My by insue. lat ed Supports 435, 55 to form a section of trans: mission line. surrounding the mast H.-

the same time they form a section oftl'ansn line. with most 12. Prefers. l-y, diamctc oi the, meet 5 i. the spa to the center transmis a M ii. 4? is such; the length, oi the composite line. [19, 41; is an integral number of half wavelengths, the number, be: cause of the physical dimensions of the; system, being two full. wavelengths or more;

The high frequency waves from he transmitter e pp-l ed over the leads Hi. toe. resonant circuit which may comprise thestub transmis. sion line formed of the parallel conductors 48, Q9; These conductorsv are short-circuite and nec ed to H at one end a he H 5 and are openmlrcuited at the. other end. The (B frqnn the transmitter are connected to the points 53 and the ends 5! of the loops ill jlre connected by means of leads 5; to sym e'trically spaced points 53 on the conductors H}; and

the points 553 being displaced from the points Similarly, the ends 54 of the loops MI E! be connected by conductors 55 to s mmctric'all'y spaced points on the conductors 48, ii

The points 56, 5:3, 55 are 50 located on the transmission line conductors Ml, 4:5 that impact-- ance matching between the component parts or the system is obtained at, each of these points.

Thus. sierensiiee ueenthe v lta e desired t b imeresseei acro s he conduc ve oose it. 4?, the Poin s. 53 may be locat db tw nith open nd e? the con uctors 48. 5% aneithepointseel inst ad o the ocation infiiafl- Usually, however, the mints 5, a el ocateo between the points/.53 t e sho t-slimmed. end of the conductor 48, 49, the d stance between the po nts-'53,. fis -3% eetermined y the voltase drop in he loops i0, 51 around thcmast H. Similar-131,512: enqing upon the length of. the elements L 41, it may necessary the. transpose the conductors]! so-that the conductorsfl, 55 connected tocor-iductor l8, for. example, are connected respectivelyto the-point, at on the loop It and thepoint 54 'onloop 47. Such transposition. may be required for matching the phase of. currents at the. ends or theloops k0,. Al with. currents invthe conductors 68., 4.8. In all. cases-of course/the location of the/taps onthe transmissionline conductorsffl; Q5 is such that the desired termination imped ance and voltage of the connected clementsis obtained. 7

In the aneratiouofi the antenna of Fig. I, the loops ll, 4?: jointly iormasection of transmission line with respect to the grounded mast ll. 'T his sectionis terminated for. reflectionlcss transmission 'of At thesame time, the closely spaceti.loops i0, 4? form a section of transmission line; inwhich cur-rents flaw in opposite directions, Inzavertical direction; that is, adirection parallel Withthe of the mast H, the electromagnetic field-s produced by these currents are neutralized and. cancelled sov that thereis no radiation along the axis of the mast H. However, in a hqri reenter}. direction, the fields of the currents in the two-loops tit, H are additive so. that the antenna system produces radiation which is concentratedsuhstantially in a, horizontal plane. con'cluce tive. mast I l reflects energy radiated inwardly firom. the loopathe distance between the loops iii, fland mast it being such that this energy reflected from mast" i l reinforces energy radiated outwardly from the loops.

In order to 'obtain still more vertical directivity in. an antenna of the type shewnin Fig. 6:, a plurality of assemblies may be employed, spaced. apart vertically approximately wave length. Two such assemblies are shown schematically in Fig. 9. The assemblies are interconnected in the same phase by a suitable impedance matching line. H. A suitable transmission. line 42. may be used to transfer energy between transmitter 39 and is connected. to the line. H at a point midway'between the assegnblies. Thedirectivity pattern for the system of Eig. 9 is represented by the lobes 43in Fig. 8.

In. :order to support the assemblies in operatime position, there may be provided a mast ll as in Fig.6.. The loops 30 may be secured to the mast by means of members 45 of insulative material and the parasitic director elements 36 may be supported ljrom the loop 39; by similar sup ports '46 which are preferably connected to the elements 38 at points of minimum voltage.

A plurality ofassemblies ofthe driven director type illustrated in Fig '1 may likewise be emp oyed toform a composite antenna structure for radiating greater amounts of power. Such assemblies individually have a very small amount of radiation along theaxis oif a supporting mast. They should be spaced'apart ve'rtieally on 'themast, therefore, by such distances that: their fields in-a. horizontal direction are additivse. i

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high frequency antenna system comprising a substantially closed loop, a second loop spaced outwardly from said first loop to form a section of transmission line therewith terminated for refiectionless transmission of energy thereover, the ends of said first loop terminating in means providing substantial capacity therebetween, and a transmission line connected to said first loop on each side of said capacity, said first loop being sufliciently less than one-half wave length in circumference to provide substantially uniform current therein.

2. A high frequency antenna system comprising a substantially closed loop, the ends of said loop being closely spaced and terminating in a means providing substantial capacity therebetween, a transmission line connected to said loop on each side of said capacity, said loop being substantially less than one-half wave length in circumference, and directive means for said system comprising a plurality of separated conductors uniformly spaced outwardly from said loop a distance substantially equal to one-quarter of a wave length and lying substantially in the same plane therewith.

3. A high frequency antenna system comprising a substantially closed loop, the ends of said loop being closely spaced and terminating in means providing substantial capacity therebetween, a transmission line connected to said loop on each side of said capacity, said loop being substantially less than one-half wave length in circumference, and directive means for said system comprising a plurality of separated conductors uniformly spaced outwardly from said loop a distance substantially equal to one-quarter of a wave length and lying substantially in the same plane therewith, said conductors terminating in means providing substantial capacity between the en-ds thereof.

4. A high frequency antenna system comprising a pair of substantially concentric, substantially co-planar loops, said loops forming a section of transmission line terminated for substantially refiectionless transmission of energy thereover,

both of said loops being peripherally incomplete, and means connected to both of said loops at the free ends thereof for supplying high frequency energy thereto, whereby said inner loop acts as a radiator and the outer of said loops acts as a director.

5. A high frequency antenna system comprising a vertical cylindrical conductive member, a pair of substantially concentric, substantially coplanar loops encircling said member, both of said loops being peripherally incomplete, the outer of said loops being'closely spaced with respect to the inner of said loops and the inner of said loops being spaced from said member by a distance substantially equal to one-quarter of a wave, and means connected to said loops at the free ends thereof for supplying high frequency energy thereto, whereby said inner loop acts as a radiator and the outer of said loops acts as a director.

6. A high frequency antenna comprising a conductive mast, a pair of substantially concentric, substantially co-planar conductive loops surrounding said mast, said loops being peripherally incomplete, the inner of said loops and said mast forming a section of transmission line terminated for reflectionless transmission of energy thereover, and means supplying high frequency currents to both of said loops, the currents in said loops having a difference in phase determined by the spacing between said loops.

7. A high frequency antenna system comprising a plurality of vertically spaced assemblies, each of said assemblies comprising a metallic loop-like member, having a pair of ends spaced apart by a small distance, conductive means coupled to said respective metallic members and concentric and co-planar therewith, a source of high frequency signals, and means supplying high frequency currents from said source to the respective ends of said members, said members being spaced apart vertically by an electrical distance and the phase of the currents supplied to adjacent of said members being such the fields of said assemblies are additive in the same direction.

8. A high frequency antenna system comprising a vertical cylindrical electrically conductive member, a metallic loop-like member substantially encircling and coaxially disposed with respect to said vertical member to form therewith a sec tion of transmission line terminated for reflectionless transmission of energy thereover, said metallic member having a pair of ends spaced apart by a small distance, a source of high frequency signals, means supplying signals from said source to said ends, and conductive means coupled to said metallic member and concentric and co-planar therewith for increasing the directivity of said system.

9. A high frequency antenna system comprising a cylindrical electrically conductive member, a pair of concentric co-planar conductive loops coaxially surrounding said member, said loops and said member forming a section of transmission line terminated for reflectionless transmission of energy thereover, the outer of said loops being spaced from the inner of said loops and the inner of said loops being paced from said member by an electrical distance substantially equal to one-quarter of the Wave length at which said antenna operates, and means connected to said inner loop for supplying high frequency energy thereto, whereby the inner of said loops acts as a radiator and the outer of said loops acts as a director.

10. A high frequency antenna system comprising a vertical electrically conductive member, a pair of substantially concentric, substantially coplanar conductive loops coaxially surrounding said member, said loops and said member forming a section of transmission line terminated for refiectionless transmission of energy thereover, both of said loops being peripherally incomplete and having a pair of spaced ends, a resonant circuit, and means connecting said ends to spaced points in said circuit.

11. A high frequency antenna system comprising a pair of substantially concentric, substantially co-planar conductive loops coaxially spaced from an electrically conductive member, each of said loops being peripherally incomplete and having a pair of spaced ends, a resonant circuit, and means connecting corresponding ends of said loops to symmetrically spaced points of said circuit, said loops forming a section of transmission line terminated for reflectionless transmission oi. energy thereover.

12. A high frequency antenna system comprising an electrically conductive member, a pair of concentric (ac-planar conductive loops coaxially surroundin said member, each of said loops being peripherall incomplete and having a, pair of spaced ends, a section of transmission line, means supplying high frequency waves to a first point on said line, means connecting corresponding ends of said loops to symmetrically spaced points on said line, the points of connection of said energy to said line and of said ends to said line being so spaced that high frequency waves are transmitted from said first means to said loops substantially 15 without reflection.

GEORGE W. FYLER.

10 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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