US2682050A

US2682050A - Localizer antenna system

Info

Publication number: US2682050A
Application number: US209431A
Authority: US
Inventors: Alford Andrew
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-02-05
Filing date: 1951-02-05
Publication date: 1954-06-22
Anticipated expiration: 1971-06-22

Description

June 22, 1954 A. ALFORD 2,682,050

LOCALIZER ANTENNA SYSTEM Filed Feb. 5, 1951 3 Sheets-Sheet l INVENTOR.

Andrew 47 MW rimf A. ALFORD LOCALIZER ANTENNA SYSTEM June 22, 1954 3 Sheets-Sheet 2 Filed Feb. 5, 1951 INVENTOR. And fllf q BY A;

Ili Mm Patented June 22, 1954 UNITED STATES F TENT OFFICE LOCALIZER ANTENNA SYSTEM Andrew Alford, Cambridge, Mass. Application February 5, 1951, Serial Nd. 209,431

13 Claims. (01. 343-407) The present invention relates to a combination antenna array and more particularly to a localizer antenna system. In the present invention, the antenna. system comprises two arrays, a main array and a subsidiary array. The main array is intended to produce the principal localizer course as for instance along a landing'runway for an aircraft. The subsidiary array essentially provides the back course but bothof these elements cooperate with one another to effect and establish a complete localizer system.

Both arrays are essentially unidirectional, although the: subsidiary array which provides the back course sends out a substantial signal at right angles to the course. are operating, there is a signal in all directions so that the aircraft approaching from a distance in any direction will be able to pick this signalup and use it as a landing guide. The subsidiary array is energized with a carrier frequency which is between and 'kilocyc1es higher or lower than the frequency of the carrier used to energize the main array. Butxthe same modulation is used onboth arrays so that the-signals received bythe aircraft receiver after demodulation are identical whether they come from'the'rnain array or the subsidiary array and in fact the listener or observer willnot know whether the main'or the subsidiary array is responsible for the .sig nal. For instance, if the main array has a car'- rier frequency of 110 megacycl'es and the sub sidiary-array: is energized 5 to 20 kilocycles higher or lower than that frequency" then the frequency of the subsidiary array would be 110.005 to 110K020 megacyc1es'or'109.080 to1091995 mega cycles. The modulating frequency will be an audio frequency of perhaps QO'cycles for the right antenna of the system and 150 cycles for the left antenna of the system.

The fact that the carrier utilized in the two arrays are of diiferent frequencies results in two benefits; (A) The interference in the overlapped regior rbetween the'patterns of the main and of the subsidiary arrayis avoided. (Bl Reflections frm obiiects in=the field of the subsidiary array cannot produce an interference pattern along the main course, so that sharp bends in the main course resulting from objects outside the radiation-pattern of the main array are avoided. To take fulladvantage of this arrangement, it is desirablethat the main array be desi nated in such a way that its overall radiation pattern would occupy as narrow a, section as possible; The narrowerthis sector is, the less chance thereis that there will be-a hangar; telephone wires; or

When both arrays other reflecting objects which could produce an interference pattern and, therefore bend along the main course.

The present invention does not relate to the receiving circuits other thanthe antenna system nor to methods of providing indications and any suitable standard arrangement which are now known and employedmay be used for this system.

It will be seen from the specification as set forth below that the main array comprisespreferably two narrow beams producing a left beam and a right beam which will be energized with the same audio frequency modulation corresponding to the left and right lobe of the subsidiary array so that'a resultant composite-signal may be received in the receivers on the aircraft and may be used to produce an indication on a meter showing that the aircraft is on the right-side of the beam, the left side of the-beam, or right on the beam. The virtue of this combination is that no matter-in what-direction the aircraft is approaching the landing strip and no matter where the aircraft is, as long as it is within the range of the subsidiary array, that a positive and definite indication will be given to the aircraft. Without this combination, it is possible for'the aircraft to miss the beam entirely, particularly if the beam is very narrow,'since the aircraft may pass through the beam before the observer has an opportunity to notice that he is in the beam.

Without further describing the merits and advantages of the present invention, the invention will be described in connection with the drawings illustrating an embodiment thereof in which:

Figure 1 shows somewhat schematically a general layout of the whole system.

Figure 2 shows a localizer radiation pattern of the'main and subsidiary array.

Figure 3 represents a so-called dumbbell pattern.

Figure 4 represents a calculated cloverleaf pattern of the radiation of the same antennas used in producing the pattern of Figure 3.

Figure 5 represents a calculated pattern of the radiation of the outer elements of the array of Figure 1.

Figure 6 represents a calculated pattern of the radiation of the central pair and the next adjacent pair of antennas of Figure 1.

Figure 7 represents a calculated total c1over leaf pattern of the radiation of the array of Figure 1.

' Figure 8 represents a calculated localizer pattern combining both cloverleaf and dumbbell patterns of the array of Figure l; and

Figure 9 shows a full wave dipole which may be used as the end array element of the structure of Figure 1.

In the arrangement shown in Figure 1, the main array comprises elements I, 2, 3, 4, 5, and 6 arranged in a straight line at right angles to the projected course with each element being used for producing both left and right beams of the type illustrated in the composite pattern of Figure 8. Antenna elements 3 and 4 are each ap proximately half wave dipole and so also elements 2 and elements 3 and 4 forming one pair and

elements

2 and 5 forming a second pair. Elements l andrfi are one wavelength'long and may be constructed as shown in the structure of Figure 9. Each of the elements may be provided with corresponding reflectors I, 2", 3', 6', 5, and 6 with the antenna units all on the same side of the reflectors. The central pair of units 3 and d are fed by a coaxial bridge '5 which preferably is of a type described in my application, Serial No. 175,694, filed July 25, 1950. The

units

2 and 5 are fed in opposite phase through a transformer 8. The full wave- 4 through the coaxial bridge by means of the transmission line 5 and energized in opposite phase. The calculated patterns for the combination of

antennas

2 and 5 which are also fed in opposite phase is somewhat like the arrangement of Figure 4: except that the radiation lobes may be somewhat narrower and two auxiliary lobes are present, symmetrically positioned at a greater angle from the line of the course than the two main lobes.

A calculated pattern of the radiation of ele- 'ments I and 6 when energized in opposite phases is shown in Figure 5. This calculated pattern shows that there are 2 sets of auxiliary lobes on on the outer sides of the pair of main lobes and that .inthiswcase the main and auxiliary lobes tend to be narrower than in the case of the com- I bination of

elements

2 and 5.

length antennas I and ii are also fed through v the transformer 8 in opposite phase and the coaxial bridge I is also fed from the transformer by means of the transmission line 9. It will be noted in the arrangement of Figure 1 that the antennas I, 2 and 3 are energized in the same phase and 2, 5 and 6 are also energized in the same phase which is opposite, however, to the phase of energization of the antennas I, 2 and 3 so that on each half of the course the antennas are fed in the same phase but Opposite to the antennas on the other half of the course. This applies to the so-called cloverleaf energization of the antennas. The transmission line 9 which impresses its energy into the coaxial bridge at its lower end has a balanced output by means of this feed through the arms l8 and i I which are in the same phase so that the feed from the arms I0 and II to the antennas 3 and i respectively are connected in reverse phase as indicated by the connecting elements I2 and I3 respectively. The construction of the coaxial bridge of the applicant as shown in his copending application also indicates that when the coaxial bridge 1 is fed by the transmission line H! into the top end of the coaxial bridge, the outputs in the arms It and II are in opposite phase so that by effecting connections 52 and It as shown the result is that the energy fed by means of the line It will be in phase in the antenna structures 3 and d. The'transmission line feed it in the present system has been given the name dumb-bell feed while the feed by the transmission line 9 is given the name Cloverleaf feed. The pattern resulting from the combination of 3 and i when the energy is in the same phase results in a single lobe symmetrical with the line of the course, whereas when the energy in the antennas 3 and 4 are in opposite phase, two lobes are provided which together should form a symmetrical pattern with the line of the course.

Figure 3 shows a calculated dumb-bell pattern, that is, a pattern obtained by antennas 3 and 4 when fed through the coaxial bridge by means of the transmission line M so that antennas 3 and 4 are energized in the same phase.

Figure 4 shows a calculated pattern of radiation of the same antennas 3 and t when fed 'The' combined calculated pattern of

elements

2, 3, 4 and 5 shown in Figure 6 provides a cloverleaf pattern of two lobes symmetrical with the line of the course, each lobe being narrower or more directive than the calculated pattern for the center pair previously described.

The total pattern combining all'of the six elements except the in-phase radiation of

elements

3 and 13 obtained through the coaxial bridge I,

by energization over the transmission line I4 is shown in Figure 7, the purpose of the combination being to emphasize the main lobes and reduce the auxiliary lobes. .The ultimate result which is the combination of energization through the cloverleaf and dumb-bell patterns is shown in Figure 8 and indicates that the left main lobe and the right main lobe overlap in a symmetrical center region directed along the axis of the course and subtending a comparatively narrow angle. It should be noted that each of the full wave end radiators are considered the equivalent of two half-wave radiators.

This resultant main array produces a difierent signal on one side of the course from that on the other so that when the aircraft, for instance, or whatever device which may have the listening apparatus is observed, the beam patterns will provide a balance when on course and left or right signals'when to the left or right of the course respectively. The means for providing this indication itself may be any of the usual apparatus used for this purpose and does not in itself form a part of the present invention.

The radiation elements I to 6 produce the main array. The subsidiary array is produced by the two radiating members I5 and I6 which are also symmetrically positioned with respect to the line of the course. These radiators I5 and I6 may be cylindrical or oval in cross section with air gaps I? and I8 respectively symmetrically positioned on one side of the shell parallel to the axes thereof. The radiators I5 and i5 comprising the subsidiary array will be energized from a high frequency source I9 whose frequency will be between 5 to 20 kilocycles higher or lower than the frequency of the carrier source 20 used to'energize the bridge circuit 2! for the main array. The subsidiary array comprising the radiators I5 and I6 will be modulated preferably by an audio frequency source. This may be accomplished mechanically by the motor 22 provided at each end with shaft extensions 23 and 24 carrying disks 25 and 26 which are provided with uniformly spaced teeth which rotate in a plane between the difierent sides of the

transmission lines

21 and 28. If the disk 25 is provided with three teeth and the disk 26 with five teeth, then the moduaesagoro:

oftthe: radiator Hi, 159 cycles-pervseoondzcl.The:

motor- :22; and; the: motors!) for the main zarray; are'drivenezsynchronously oronermotoremayeserve to rdriveithe shafts 2-3523f2l1l1173h'32 so thatithe diskslflsand al -which are :similar respectively to therdisksafizandifisfitwilliprovidecthersame modu lation; iorethe; left and; rightrisidetofsthe array: system. The coaxial transmission; abridge 211 changes :the phasewof 1 energyrfedithrough"the: branchirtw to be opposite from that. fed: through; therbranc'h 4| sothatif the carrier is modulated by 90 cycles by the zdisk.-33;: thetenergy-atlniouglr therbranch: 4!] will nc'omei out-in opposite phasei'to that onfthe energy in thei'branchf lL: .,Therenergyt through the branches r42 and lfi will, howeve'nbe in the samecphase, and-in phase with the: energy: fed" through branch. 4 I .1 The. energynf each outletofthetransmissionzbridge 21 goes. through the baiuns35 and 36 respectively ltorthe transformer 8 and? to the transmission-:-'line l4 respectively; The balunsareessentially a balancing element: usedrgener'ally in ;:the. art; forv a description of which reference is had to an article in VeryrI-Iigh': Frequency Technique? vol; 1, Chapter 3, by Radio Research" Laboratory. Staff; 'published' by Mo:- Graw-Hill, 1 947: x

Since-:the power :deliveredto the 1 cloverle'af should bee-about one-quarter of the power de-= livered to the dumb-bell, an. adjustable :attenuator 31 is providedtbetween the:balun 35 and the transformer "8. This'zattenuator is adjustedto obtain a balancebetweenthe fdumbebell and cloverleaf DHZCIGGIIIS'ISO' that Itheeultimate pattern produced: willzbeislibstantially' asashown "in Figure 8:

Figure ,2 which shows a composite'pattern of the: main andrsubsidiary arraysis 'shown as -hav ing two-main lobes. A and. B, the: left lobevA lying mestly to the-leftof the course linec andr-the lobe B to the right 'of the course line: rThensignalgivenebym-the -left l-obeaA willxcorrespondito the 4 modulation-of themodulating. element 33 Which; may be 90- cycles per second; while the modula=a tion corresponding to the 'rightlobe B will be: #150 cycles per second, because of the modulatingiele merit-:24. Thisnapplies also for the-dotted main subsidiary lobes D and E, respectively; the :lobe D having :a modulating frequency corresponding to the modulating element 25 Ethe lobe E has a modulating frequency corresponding to the modulating element 26. Along the course line C,

thei'stwo signals are balanced and, "therefore," a balanced mdicator-"mayv-be"used to indicate that the pilot is on this course. If the pilotshould deviate to the left of the course, the signal from the'-lobe A wiltprevail, while if The deviates-to therightof' the course; the signal on the lobeB willprevail:

Thesubsidiary'array in the present invention is intended to provide a back course in which this array sends out a substantial signal at right angles to the course. This will be evident from the lobes D and E in Figure 2 from which it will be seen that the subsidiary array is intended to cover directions other than those in which two main lobes are situated. Since, however, the modulation of the subsidiary array and the main array lobes correspond, the operator will not realize that he is listening or observing one or the other of these lobes. The subsidiary array is far less strong in the forward direction of the in Figure 9:

6 beams n :amtsB than sth'erit-beamswn andz Bso' thatatheelsubsidiary arrayzawilllnot ..-be':-. dominant inithesessections;

The factors? controlling the deviation of. the: beamsifromthecentra1-courselineare first that theitradiators on the." right and the left side -of the" oenter'are fed inopposite phases and secondly that while the dumb-bell is fed with modulated carriersrin add itive'phaseythe fcloverleaf is fed 5 with'zonexmodulatedcarrienin:oppositezphase to that of the other modulated carrier throughthe: transformer 8-. 1 The'resulting patterny-therefore, asexplained in Eigurefl is obtained:

The

radiators

2, 3, 4 and S are preferablybal anced slot fed dipoles of half wave lengthven' ergized through: the coaxial transmission lines extendingthroughzthestem of the T as indicated diagrammatically in Figure l.

The end radiators are azfull wave length and a full section of rthefstructure 'for: thesev radiators is shown in Figure:9. This structure is essentially an aarray'of two 1 half wave length. elements placed-:nexttoeachnther. The-feeding arrange-- ment, however, is simpler than that-for'a halt; wave-element;

The outer conductors of thetwo half waveele--- ments consist of two Ts 51 rand -52- which in sectionimay-belzcylindrical, ovalor other type:v of section: commonly "usedv 1 as a "coaxial "transmission H-line. Here #the :conductor designated as ey lindrical-is intended :toi'inclu-de --other types :of

sectionssas'well. The full-wave element is fed: through thewstemofone T. i This comprises the outer conductive cylinder-.53 and the inner: cylinder 54 forming'a coaxial transmission line. The:

inner cylinder 54 is spacedv-and insulated from. the outer cylinder "and is' connected :at top: to-

the inner conductor '56 concentrically positioned within the right haltof the: outercrossbar'55" by the conductive-strapS-l. Theinner conductor 56; is :insula'tedvby; suitable insulator disks from therouter=-conducton55 and connects through ins:

sulating .end :cap .58 :to the cap 62 *of the crossbar of the: outer-conductor 63 :Of the;

conductive connection tromthe terminal-=60 to the terminal-6|" of the conductive cap 62, atrthe inneraend ofcthe cylinder 63 which forms-the:

cross barfor the T 52:

In -a constructionnzwh-ich. I have successfully: used; the impedance between the ends of i the: Ts was approximately. 650 ohms matche'drtoa 52.5-ohm line byatransformer having a Zn of 184- 011-1115;

The :designs: of :t-he full wave' element is 'such that .thereare small currents flowing along the stems: of both Ts. These-currents fiowriniop posite directions in the two stems: At first it was believedthat-=this-might:result in excessive radiation-torvperhapsfevenein minorloads in the cures: tion.atu'ight'anglestofthefstemszs The only effect of 1 the stem rcurrentscis to tbroadenslightlythe T at;=the: right A conductiye'strap 259 *makes 'a good.

7 nitude of radiation in the direction of the beams than the beam radiations, the beam and the broad lobe radiation on one side of the. course having the same modulating frequency and the beam and broad lobe radiations on the other side of the course also having the same modulation frequency but differing from the firstmodulation frequency.

2. A system as set forth in claim 1 in which the modulating frequencies are in the low audible range.

1 3. A system as set forth in clainrl in which the modulating frequency of 'one group is in the vicinity of 90 cycles and the other in the vicinity of 'l50 cycles.

4. A- system as set forth in claim 1 in which the beam patterns are directed generally slightly to the left and right of the course respectively and the otherradiation lobes are mainly to the sides and rear of the beam patterns. I

5. A system as set forth in claim 1 in which the broad lobes have a carrier-which is'in the range from 5 to 20 kilocycles higher or lower than the main carrier.

6. A localizer signaling system for'g'uiding a craft along a course comprising a main array for producing a pair of intersecting lobes one directed to the right and the other to the left of the course and a subsidiary array for producing'lobes to the right and left of the course of lower intensity than the beams, means energizing the elements of the arrays to the right of the middle of the array in opposing carrier phase for that of the elements to the left of the middle, means for modulating the carrier of the main array with two different low frequencies in opposing phase and the pair of main array elements'adjacent the middle with the two different low frequencies in the same phase.

' '7. A system asset forth'in claim 6 in which the pair of main array elements adjacent the middle are energized with the two different low frequencies in the same phase at approximately four times the power as the energization of the main array elements in opposing phase.

- 8. In' a localizer'system of the type described, a main array having a plurality of radiators substantially at right angles tothe intended course, a coaxial bridge element energized simultaneously at both ends having opposing side outlets connected to the middle positioned elements of the array, said coaxial bridge element having means for reversingin phase the energy fed to one end from that of the energy fed to the other end and means for feeding the other elements of the array through a transmission line having the same phase as the energy fed to one end of said coaxial bridge.

9. In a localizer system of the type described, a main array having a plurality of radiators substantially at right angles to the intended course, a coaxial bridge element having two input ends and two output ends with means containedaesaoao.

therein for reversing the phase of the outputs .fed' from one input end from that fed from the other input end, feed lines connectedfrom said outputs to the middle positioned array elements, a balanced transmission bridge, a transformer;

energizing means for energizing said transmission bridge and still further feed lines connecting from the output of said transformer directly to the other elements of said array.

10. A system as set forth in claim 9 inwhich the energyfed through the transformerhas approximately one fourth of the power as the energy fed directly. to the coaxial bridge. .11. A system as set forthin' claim 9 in which means are provided between the balanced trans mission bridge and the transformer for attenu-' ating' the power passing therethrough to approximately one'fourth that fed directly from the balanced transmission bridge to the coaxial bridge.

12. A system as set forth in' claim 9 in which the means for, energizing said transmission bridge includes means for low frequency audio 'modula' tion of the carrier wavewith two diiferent frequencies each in different feed lines to different sides-of the transmission bridge, said transmission bridge having one arm effecting a reversal of phase of power passed therethrough;

' 13. A localizer signalingsystem for guiding a craft along a course comprising a group of antennae forminga main array and a group of antennae forming subsidiary array, means energizing individual antennae of said main array to produce dumb-bell and cloverleaf radiation patterns respectively, and to form together a pair of main composite beams directed to the left and right of the course respectively but over-' lapping narrowly along the course, means for producing with said subsidiary array radiation patterns of substantially rounded lobes to the right and left of the course and intersecting narrowly on the course of substantially less intensity than the beams of the main array and means for modulating said arrays with different audio frequencies for the right and left lobes respectively-whereby the direction of the course may be established.

1 References Cited in the file of this patent V UNITED STATES PATENTS Number Name Date 2,212,238 Kolster Aug. 20, 1940 2,283,677 Kandoian Mayl9, 1942 232L454 Brown June 8, 1943 2,402,3'78

Davies fl l June 18, 1946