US2259124A - Four-course beacon - Google Patents

Description

Oct. 14, 1941. E. N. WENDELL FOUR-COURSE BEACON Filed Sept. 30, 1958 m w 3E NQE .inglmeans;

Patented Oct. 14, 1941 7 2,259,124 FOUR-COURSE BEACON .Edward N. Wendell, Rockport, Mass, assignor to International Telephone Development Co. Inc.,'

New York,'N. Y., a corporation of Delaware Application September 30, 1938, Serial No. 232,524

6 Claims.

The present invention relates to radio beacon transmitting systems and especially to transmitting systems for radio beacons of theso-called four-course typev whose radiation pattern is adapted to define four courses or flying paths extending radially from the position of the beacon.

It is an object of the present invention to provide a radiating systemof particularly simple design which requires only three dipole antennaev for producing a four-course beacon pattern. It is a further object to provide such a system in which the transmission line arrangements for feeding the. different antennae are likewise simplified and in which the keying arrangements are particularly simple. It is an especial object of the invention to provide such a radiating system in which the power to be radiated is not required to pass through the key- In accordance with .one feature of the present invention three vertical dipoles triangularly arranged at the apices of an isosceles right triangle are energized so as to produce-a symmet- 'rical four-course radiation pattern. In accordance withanother feature of the present invention one of the three vertical'dipoles is constantly energized and the energizationrof the other two is alternately controlled by keying 7 means through which the power. to be radiated does not pass. 1 v

In accordance with another feature .of the present invention the arrarn'ement of the transmission lines and keying means for feeding the three antennae'is such that the system requires nocorrecting adjustment since thepattern produced is inherently symmetrical and balanced.

-One particular advantage of-the arrangement is that the field strengths of the different lobes of the produced radiation pattern are so related to each other and tothe field strength produced during the keyingtransition that along each of the four-course lines the field strength remains constant; throughout the transition from one keying condition to the other keying condition; thus'obviating key clicks and facilitating the, accurate determination of the correct on course position. v v

' The nature of the invention may be best understood by reference to the attached drawing in which Fig. 1 represents-a radiation system in accordance "with the present invention; Fig. 2 represents the radiation pattern produced by the radiation system of Fig. 1: -Fig'. 3 represents another form of radiation system embodyingmy invention. l

Referring more particularly to Fig. 1 vertical dipoles I, 2 and 3 are disposed at the apices of an isosceles right triangle whose sides. .are /2 wavelength, and .707 wavelength long respectively, the central dipole 2 being disposed at the angle of the triangle. .A supply line 4 which is fed from a suitable unkeyed source of continuous waves (not shown is connected with the,

center of dipole 2 so as to continuously feed this dipole as shown. Auxiliary feeder lines 5 and 6 extend from the center of dipole 2 to the centers of outer dipoles 3 and I, respectively, so as to feed these dipoles. tend respectively from the intermediate junction points A and B of feeder lines .5 and 6 to the common keying device 9. The keying devices may be a motor-driven or clockworkloperated switching means but is preferably a. relay con-.

trolled .over a suitable signal .line not shown. Whether the keying device '9 be self-contained or externally operated its essential function is to short-circuit lines 1 and 8 alternately in accordance with the desired keying code, such as for example the well known a-n code'in commen use for beacon signals. Preferably the switching mechanism of the keying device 9 is arranged so as to break-beforeemake; inother words the switching mechanism is adapted. to remove the short circuit fromline I before-short circuiting line 8 or vice versa. In 'any'case, however, the interval between theremoving of the short circuit from one control line and the short circuiting of the other control lineshould be as short as practicable... r

Junction points A and B are each located A wavelength from the dipole 2; thus, sinceyithe feeder lines 5 and 6 are each wavelengthlong, the juncture points are centrally disposed along their respective lines. .If, however, the length of the lines 5 and 6 arechosen to be other than the preferred value of /2 wavelength the junction points A and B should not be centrallydis: posed but should be located wavelength from the dipole 2. Similarly the lengths of th'econtrol lines 1 and 8 are each fl wavelength over all including the effective ing device 9. v v.

As a result of this choice of lengths the effect of short-circuitingone of the control lines, for example the control line I, at thekeying device 9 is to render the eife'ctivevimpedance of this control 'line as seen frbm junction point B substantially infinite. with respect to? the length within the key,-

Control lines'land 8 ex-- transmission of energy along feeder line to dipole 3 the control line 1 has substantially no effect at this time and therefore the dipole 3 is fully energized. Because of the half wavelength dimensioning of feeder line 5 the energization of dipole 3 is the same as that of dipole 2 but of opposite phase. The resultant radiation pattern of dipoles 2 and 3 therefore has the general form of a figure B as represented by the dot-and-dash curve'2| of Fig. 2, the direction of maximum field intensity being along the line joining the dipoles 2 and 3 and the field intensity perpendicular to the line 23 being substantially zero as shown. These conditions continue during each of the keying intervals in which control line 1 is short circuited, which may be designated the at intervals.

During the above assumed a-intervals in which the control line 1 is short-circuite-d, the control line B is correspondingly open-circuited at keying device 9 so that the effective impedance of this control line as seen from junction point A is substantially Zero. The. feeder. line 6'. may therefore be considered as. substantially shortcircuited at the junction point A during this interval and therefore substantially no energy is transmitted to the dipole Furthermore. because of the effective short circuit at Adipole I is effectively open at its center so that it is also ineffective as a parasitic reflector.v Thus the radiation pattern as above described and as illustrated by curve 2| of Fig. 2 is not distorted by the dipole During this keying interval moreover as a result of the effective short-circuit of the feeder line 6 at junction point A the effective impedance of this line 6, asviewed from dipole 2 is substantially infinite so that the power delivered over the supply line 4 is all transmitted to the dipoles 2'and 3.

Considering how one of the alternate intervals which may be designated then intervals, during which the control line 8 is short-circuited and the control line is open-circuited, the dipoles. 2 and I will become effective for radiation while the dipole 3 will become ineffective. produced by. the radiation from dipoles and 2 will again have the form of a figure eight, but as shown in the solid line curve 23 of Fig. 2, the direction of maximum field. strength will lie along the lines joining the dipoles2 and l.

In making the transition from one keying condition to the alternate keying condition the switching elements of the keying device 9 are preferably arranged so that the control line I is not short-circuited until after the short-circuit is removed from the control line Band viceversa. Thus during the transition period between alternate keying conditions only the dipole 2 is energized-so as to give an essentially circular radiation pattern. Furthermore, the impedance relation between the supply line 4. and its load terminals, i. e. the central connection points on the dipole 2, is preferably so adjusted that a more perfect impedance match exists when the dipole 2 alone is effective and both the dipoles and 3 are out of action than when one of the. dipoles such as or 3 is alsoeffective together with the dipole 2. Any suitable impedance matching means such as building-out section I0 maybe used for matching the feed line. 4. to its load. By simply adjusting such matching means, as for example by adjusting the position. and length of the building-out section ID, a matching condition can readily, be attained. such that the increased matching efficiency whichexists when dipole 2 The pattern 2 alone is efiective is sufiicient to make the circular radiation pattern of the dipole 2 exhibit a field strength along each of the four course lines which is equal to the field strength produced along such lines by either the pattern 2| or the pattern 23.

The desired relation between the field strength of the different patterns is clearly illustrated in Fig. 2 in which the curves 2| and 23 are polar intensity diagrams of the radiation patterns produced by the two dipoles 2 and I and by the two dipoles 2 and 3 respectively, whereas dotted curve 20 represents the radiation pattern resulting from the energization of dipole 2 alone.

In actual construction the three dipoles I, 2, 3. are arranged so as to be properly indicated as being at the point represented by 2 in the figure. The wide spacing shown in the figure is included merely to indicate the planes in which the radiators are provided to produce the different patterns shown in the figure. The slight displacement of the patterns may occur at points near the beacon due to the fact that centers of radiation of the two pairs of dipoles are slightlydisplaced relative to one another. However, at the distances at which the beacon is used the entire assembly of dipoles may be considered as a point source for all practical purposes, and substantially no displacement will then be observed. It will be clearly seen in this figure. that by proper relative proportioning between the field strength of the patterns 23 and 2| on the one. hand and the circular pattern 20. on the other hand a condition can be reached in which along each of the four-course lines P, Q. R, S the field strengths produced by pattern 23, pattern 2|, and pattern 20. will all be substantially alike. Although the tangent points of patterns 2|, 23, are displaced slightly because of the antenna arrangement it is clear that at the distance over which the beacon is used, the patterns will be substantially at right angles and the. courses well defined.

It will be noted that in accordance with the above suggested arrangement the condition, of equality between the transition field strength and the field strengths in the two keying conditions of intervals at and n can be simultaneously obtained for all four course directions by the. adjustment of merely one single matching means. In order to make this adjustment therefore it is merely necessary to place a receiver or monitoring'device along one of the course lines at a substantial dis,- tance from the transmitting arrangement, and then to adjust the matching means |0 until the signal strength as measured by such receiver-0r monitoring device is the same during one. of the keying intervals as it is for the transition condition between keying intervals. When this single adjustment has been made itwill be found that complete equality between all three field strengths is reached along each of the four course lines.

In accordance with another embodiment of my invention another type of four-course radiation pattern can be produced by the use of apparatus essentially like that: shown in Fig. 1 but having a transposition in each of the lines 5 and 6. Such apparatus is shown in Fig. 3. The effect of such a transposition is to make the energization of the central dipole 2 cophasal with th e energization of that outer dipole which is simultaneously active.

The resulting pattern, therefore, exhibitsa maximum field strength perpendicular to the linejoining the two dipoles which are active in the interval under consideration and exhibits; a substan tially 'z'ero field stfengthsalongithe line joining the-itwo active dipoles. with the preferred spacing of; onehalf wave" length between each of the outer dipoles and the central dipole the pattern which results from the system of Fi'gr3 has 'a' figilreeight shape generally. similar tozthat of the pattern previously described for thesystemof Fig. 1. Fig. 2 maybe therefore considered as also representing the radiation patterns of'the system of"Fig.--3,"but iwhn so interpreted it should be notedthat .the radiation pattern 2! is produced during the interval in which dipoles "Z'and I are simultaneously active while the radiation pattern 23 is produced 1 during the interval in which. dipbles 2 and 3 are simultaneously active.

T *Bec'ause 'of'the similarity between the pattern produced by the modified system above mentioned and the 'patternpro'duced by thepreviously 'de-'- scribed system in Fig. 1 either of these systems may be satisfactorily employed' incases where the dipole spacing is betweenthe' central dipole 2 a-ndthe outer'dipole are exactly one-half wave- -length as described. Sincethe system of Fig. 3 gives somewhatnarr'ower lobes and gives'a greater sharpness of definition of the course lines, it is preferred. It should be :noted, however, that if these dipole spacings are other-than exactly onehalf wavelength as in certain modified forms hereinafter described the resultant shapes of the patternswill be quite difierent for the system of Fig. 3 and that 'of Fig. 1 and therefore in some cases the system of Fig. 1 may be preferred when such modified forms are used.

In either the system of Fig. 1 or the system of Fig. 3 the keying device 9, which has been described as alternately short circuiting and open circuiting lines I and 8, may be modified so as to variably terminate such control lines by means of impedances which are other than a complete short circuit or a complete open circuit. If, for example, the control lines I and 8 are made somewhat longer than one-quarter wavelength, the keying device 9 may be arranged to terminate these control lines in reactive impedances of such value that one of these reactive impedances together with the excess length of the control line above one-quarter wavelength will together produce the effect of a short circuit, whereas the other of said impedances together with the excess length of the control line will together produce the effect of an open circuit at a point onequarter Wavelength from the junction B. In the limiting case of principal-utility the control lines are each made one-half wavelength long and the short circuiting action of the keying device is replaced by an open circuiiing action and vice versa. Intermediate lengths of the control lines with suitably chosen intermediate reactance values for the terminations are also possible.

It should furthermore be noted that either the system of Fig. 1 or that of Fig. 3 may be made to operate satisfactorily even if the impedances with which keying device 9 terminated the control lines are not purely reactive or are not so related to the lengths of the control lines as to be equivalent to open circuits and short circuits at the ends of quarter wave control lines. It is true that if the terminating impedances include a resistive component some power will be wasted. Furthermore, if the terminations are not so related to the lengths of the control lines as to be equivalent respectively to open circuits and short circuits at points one-quarter wavelength from junction B, the result will be that the dipoles will not be effective solely in pairs but rather all three dipoles. will be somewhat effective at all times. The resulting, patterns-however, will still be useful for' defining course lines a'nditxis therefore to be understood that although I prefer a system in which keying device 9: 'so'terminates the control line as to. render the three dipoles effective only in pairs, nevertheless, other :termination values; may be successfully employed.

In the above description it has been assumed that the desired relationship of the four course lines P, Q, R, S was the mutually perpendicular relationship shown in Fig. 2. In case it, is desired for some reason to vary this relationship so that the angle-between the lines PQand the lines RS is other than it is preferred to provide such displacement from perpendicular by varying the relative strengths or shapes of. the patterns 23 and 2t while still maintaining the perpendicular relationship between the dipoles I, 2 and 3 as previouslydescribed. :1

In order to effect a variation in the relative strengths of the two figure-eightshaped'patterns the power fed over supply line 4 may be modulated in synchrcnism with the opel'ationof keying device 9.

Alternatively the shapes of the patterns 2i 7 and 23 may be varied by making the spacing 'of one or both of the. dipole pairs i--2;and 23 other than one-half wavelength so that the corresponding'radiationpattern will be distorted. If the separation between the two -dipoles'are to be decreased to ,a-value slightly :less than half a wavelength. the corresponding auxiliary feeder ,line 5 or 'B'may bemaintained one-half wave length long by slightly bending or folding this line. If, however, the physical length of the feeder line cannot be maintained at one-half wavelength, as when the spacing is to be increased to a value greater than half wave length or when it is not desired to bend the auxiliary feeder line, the effective electrical length of the auxiliary feeder line may still be maintained at one-half wavelength by inserting suitable phase delaying or advancing means.

By the use of any of these expedients the division of power between the central dipole 2 and the outer dipole in question may still be maintained inherently equal. It is true that even if the eiTective electrical length of the auxiliary feeder line in question is not maintained at onehalf wavelength the corresponding outer dipole or the type comprising two concentric lines side by side, or of the balanced shielded type instead of the open wire type shown. If the concentric type of transmission line is employed suitable coupling means of known type may be used be tween the transmission line and the dipole in order to assure a balance in the energization of the dipole.

Although certain embodiments of my invention have been shown and described for the purpose of illustration it will be understood that modiiications, adaptations and alterations thereof occurring to one skilled in the art may be made without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. A radiation system for a four-course beacon comprising a first dipole, two further dipoles disposed so that said three dipoles lie at the apices of a triangle, a source of energy and means for alternately feeding energy from said source to said first dipole and one of said further dipoles and said first dipole and the other of said further dipoles.

2. A radiation system for a four-course beacon comprising three dipole antennae disposed at the apices of an isosceles triangle, a source of energy, means for continuously energizing from said source that one of said dipole antennae which lies at the apex joining the equal sides of said triangle, and means for alternately energizing from said source the other two of said dipole antennae during the energization of said one oi said dipole antennae.

3. A radiation system for a four-course beacon comprising three dipole antennae disposed at the apices of a right triangle, a source of energy, means for energizing from said source that one of said dipole antennae which is disposed at the right angle apex of said triangle, and means for alternately energizing from said source the other two of said dipole antennae during the energization of said one of said dipoles.

4. A radiation system for a four-course beacon comprising three vertical dipole antennae disposed at the apices of an isosceles right triangle,

a source of energy, means for energizing from said source that one of said dipole antennae which lies at the right angle of said triangle, and means for alternately energizing from said source the other two of said dipole antennae during the energization of said one of said dipole antennae.

5. A radiating system for a four-course beacon comprising a central dipole antenna, two auxiliary dipole antennae triangularly disposed with respect to said central antenna, supply means for energizing said central antenna for an extended time, feeder lines extending from said central antenna to each of said auxiliary antennae, a control line branching from an intermediate point of each of said feeder lines, and keying means for variably terminating said control lines during said time to control the transmission of energy over said feeder lines to said auxiliary antennae.

6. A radiating system for a four-course beacon comprising a source of wave energy, a first dipole antenna connected to said source so as to be energized for an extended time, a plurality of auxiliary antennae triangularly disposed with respect to said first dipole and connected to said source over feeder lines, a control line branchingly connected to each of said feeder lines, and keying means for variably terminating said control lines during said time to control the flow of energy over said feeder lines to said auxiliary antennae.

EDWARD N. WENDELL.

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