US3153238A - Fixed antenna system for creating a rotational field - Google Patents

Description

1954 CARL-ERIK GRANQVIST 3,

FIXED ANTENNA SYSTEM FOR CREATING A ROTATIONAL FIELD Filed March 4, 1958 4 Sheets-Sheet 1 FIG.I.

PRIOR ART STRUCTURE I I MOTOR/10 I l l I 1 souno coc I I 1 mscmmusm GEAR l4 2| us souuo MECHANISM l7 \RADO rmzouzucv GENERATOR INVENTOR CARL-ERIK GRANQVIST Bygw wl ATTORNEY Oct. 13, 1964 CARL-ERIK GRANQVIST 3,153,233

FIXED ANTENNA SYSTEM FOR CREATING A ROTATIONAL FIELD Filed March 4, 1958 4 Sheets-Sheet 2 E/ /a 2 4 L i L 1 FIG.3

FIG.4.

FIG.5.

INVENTOR CARL-ERIK GRANQVIST I BY ATTORNEY Oct. 13, 1 6 CARL-ERIK GRANQVIST 3,153,233

FIXED ANTENNA SYSTEM FOR CREATING A RQTATIONAL FIELD Filed March 4, 1958 4 Sheets-Sheet 3 COMMUTATORx I SOUND MECHANISM I Q\ R. F. Generator if 61 v MOTOR INVENTOR CARL- ERIK GRANQVIST BY 1 1 347A ATTORNEY Oct- 13, 1 CARL-ERIK GRANQVIST 3,153,238

FIXED ANTENNA SYSTEM FOR CREATING A ROTATIONAL FIELD Filed March 4, 1958 4 Sheets-Sheet 4 INVENT OR CARL- ERIK GRANQVIST a ua/1 ATTORNEY United States Patent 3,153,238 FEED ANTENNA SYSTEM FOR CREATING A ROTATIUNAL FIELD Carl-Erik Granqvist, Lidingo, Sweden, assignor t0 Svenska Aktieboiaget Gasaccumniator, Lidingo, Sweden, a corporation of Sweden Filed Mar. 4, 1958, Ser. No. 719,138 Claims priority, application Sweden Sept. 4, 1957 4 Claims. (Cl. 343-106) For different purposes in radio technology, it is desirable to provide a rapidly rotating 'field having a Very sharply limited directional characteristic. This is the case in which the transmitter antenna is used as a speaking radio beacon, while the receiver antenna is used in an automatic direction finding system. A difiiculty in these antennas has been that one could not provide the desired field rotation with the required constancy as far as regards speed without arranging all of the antenna system rotating in space. Centrifugal forces occur which were difficult to control, especially if the antenna system also was mounted in a place which was not protected against the wind pressure, so that the forces occurring from the wind pressure added themselves to the centrifugal forces. The mechanical strains were then, very often, so large that the antenna system could not afford them.

To these purely mechanical problems also some radiation electrical phenomena were added. Often the antenna system has been composed of two or even more parts of antenna systems. In speaking radio beacons it has been usual to provide a first antenna system for the purpose of transmitting the bearing indication, and a second antenna system for the purpose of transmitting, in the intervals between the times when a given bearing indication was transmitted, a so-called covering field. The covering field drowns possible existing false bearing indications which could occur when signals in a direction which should not be audible are caught by buildings, natural formations or the like in the vicinity and reflected. In receiver antennas for automatic direction finding systems, there has also been required an antenna in addition to the signal intercepting antenna, the purpose of which was to intercept the signal and rectify it for creating a control voltage for automatic volume control.

In these antenna systems existing up to now, one always had to place the auxiliary antenna either to the side of the main antenna, above or below the main antenna. None of these possibilities has functioned well. If the auxiliary antenna is placed at the side of the main antenna, then one has to contend (1) with the possibility of an angular error between the radiation characteristics of the two antennas, and (2) with the one antenna working as a reflector for the other one and transmitting signals in non-desired directions, and (3) with the relation between the field intensities from the two antennas in different directions not being the same due to topographic conditions. If, on the other hand, the antennas are placed one above the other, then certainly the said disadvantages have been done away with, but instead one has to contend with disturbing interferences by the ground reflection. In this connection, it is necessary to call to mind that here is the question about antennas for very short wave, as well as ultra short wave lengths, where the difference between the path of the direct wave and the groundrefiected wave may very easily amount to half a wave length, so that full interference with extinguishing of the signal will result. An investigation proves that this state will take place along a conical surface with the point turned downward in the place Where the antenna system is situated, and that the angle between the different generatrix lines of the conical surface and the ground will be larger, the higher up the antenna is placed. One has used this fact to decrease the risk for signal extinguishing effect through interference of this kind by'intentionally building the antennas of said kind very low to the ground. One has calculated that in such a case the extinguishing cone could be assumed to be so close to the'ground, that it would fall entirely within ranges where receivers of the signals transmitted from the said antenna, or transmitters of the signal to be received by the said antenna, respectively, will never be situated, and also that buildings, woods or the like would absorb the ground reflected wave, whereby the interference extinguishing effect could be avoided, or in any case decreased.

The application of the antenna mounted on a very low height means decreases the power of the antenna, which is not desirable. Therefore, there is a need to arrange a signal transmitting antenna or a signal receiving antenna, respectively, in the same position of height as the auxiliary antenna.

The two problems mentioned above, that is, the provi sion of an antenna for a rotating field with sharply limited direction characteristic without said antenna having rotating parts, and the placing of said antenna in such a way that the signal receiving or signal transmitting antenna, respectively, will be at the same height as the auxiliary antenna, are solved by the present invention. This invention will be further described below in connection with an embodiment including an antenna system for a speaking radio beacon.

The description of the invention will be made in connection with the attached drawings, in which: 7

FIGURE 1 shows a schematic diagram of the prior art structural arrangement of the antenna system for a speaking radio beacon;

FIGURE 2 shows a corresponding arrangement of a plan View of the diagram according to the invention, containing dipoles, reflector bars, and a quarter of a wavelength commutator;

FIGURE 3 shows in vertical projection the arrangement of same dipoles and reflector bars.

FIGURES 4 and 5 show schematic wiring diagrams in abbreviated form for a part of the dipoles contained in the antenna system;

FIGURE 6 shows the radiation diagrams in the complete antenna system according to the invention, when its dipoles are connected according to FIGURES 4 and 5; and

FIGURE 7 shows a wiring diagram illustrating how a signal generator is connected to the dipoles of the antenna system.

The invention is described in connection with a transmitter antenna for a speaking radio beacon. It is obvious that it may be used with the same advantages in connection with any antenna intended to create a' rotating field diagram, and also that it can be used in connection With receiver antennas.

The known arrangement consists of a motor 10 driving the shaft 11 together with the antenna 12 mounted thereon, said antenna being composed of dipoles and intended to transmit bearing indications during its rotation. The composition is of such a kind that the antenna will give a' strongly limited directional field diagram, a so-called cigar-formed diagram, containing the two lobes 13. For this purpose, the motor lll is also over a cog gear 14 connected to a tone machine. A modulator 16 obtains its radio frequency current from a generator 17 and gives off current after modulation with the bearing indication information to a commutator 18 and by means of this to theantenna 12.

Above the antenna 12 an auxiliaryantenna 19 is applied; This is also'of the dipole character, but its dipoles are arranged in such a way that the field transmitted will radiate according to the characteristics 20. It is seen from the drawing figure, that these characteristics form a figure similar to the figure 8 and have such a direction that the lobes of the characteristic 13 will fall generally in the angle between the two lobes of the characteristic 20. In any direction in relation to the speaking radio beacon, one will therefore alternatively hear the signal from the antenna 12 during an angle of approximately 25 to 35, and the signal from the antenna 19 during an angle of approximately 145 to 155 thereafter with the same division of degrees again hear the signal from the antenna 12, and finally during the remaining part of the turn the signal from the antenna 19.

As already mentioned, the signal from the antenna 12 is modulated with a spoken indication about the bearing on to the beacon at the moment when the listener hears this signal. In order to avoid that, the signal in question when it has another value is refiecte'd by means of objects in the surroundings and erroneously being heard in the direction just mentioned. The signal from the antenna 19 is provided with a covering tone, a so-called covering field, modulated on the same carrier wave. The carrier wave is also derived from the generator 17, but it is modulated in a tone mechanism 21 with the signal of the covering field and by means of the commutator 18 transferred to the antenna 19.

It may now occur that a directly radiated wave 22 and a ground reflected wave 23 from the antenna 19 meet at the observation point 24 with such phase displacement (180) that the two waves extinguish each other or at least substantially weaken the signal strength of the received signal and the purpose of the covering signal will no longer be fulfilled. This in the first place is depending upon the signal intensity from the antenna 19 having been so strongly decreased at the point 24 without the signal intensity from the antenna 12 having been decreased in the same relation. On the other hand it may occur that the signal intensity from the antenna 12 at another point will be decreased to a corresponding degree or brought to zero value without the signal intensity from the antenna 19 being decreased to a corresponding degree. This lack in balance between the signal intensities depends in its turn upon the two antennas 12 and 19 being situated at different heights above ground.

According to the present invention the antenna itself is fixed and is thus not put into rotation. It consists of a number of dipoles 25 (FIGURE 3), arranged in the form of a cage together with a corresponding number of grounded bars 26 being mutually connected. The number of bars are the same as the number of dipoles, or the double of this number or the like, so that the grounded bars 26 form a screen. Each one of the dipoles in the antenna ring is connected with a fixed means in the commutator 27 (FIGURE 2), whereas the corresponding means in the commutator 27 are arranged to rotate in a way which will be further described in the following.

For a more detailed explanation of the action of the antenna system, it is assumed that at a given moment the dipoles 2833 are connected to the conductor from the modulator 16 in a way shown in FIGURE 4. Regarding the extraordinary short wave length of oscillations concerned, it is thereby important that the conduits to the different dipoles have the correct length. They are therefore combined to connection points 34, 35 in immediate vicinity of the dipoles by means of conductors 36 11 of adapted lengths, and the connection points 34 and 35 are in turn combined to a further connection point by means of exactly equally long conductors 42 and 43, respectively. The connection point 44, finally, is connected to the tone machine and modulator 16 by means of a conductor 45, the length of which is not critical.

The wave front corresponding to either one of the lobes 13 will now due to its symmetry radiate in the direction 46, FIGURE 2. In order that the same form of the characteristic shall be obtained, as in FIGURE 1, it is therefore desired to give the dipoles 30 and 31 a lag corresponding to the radial distance A between the level through the dipoles 3G and 31 and the level through the dipoles 29 and 32, whereas one is giving the dipoles 28 and 33 a lead of the value A equal to the radial distance between the dipoles 29 and 32 and the level through the dipoles 28 and 33. If the number of dipoles is sufficiently great, then one can with allowable approximation regard A =A =A. If, on the other hand, the number of dipoles should be small, regard must be taken of the ditterence betwen the two values. The said lead or the said lag, respectively, is provided by adaption of the lengths of the conduits 36, 37' and 38 as well as, in a symmetrical sense, of the lengths of the conduits 41, 40 and 39. If, for instance, at a given moment, the phase position of the current to the dipole 29 should be equal to then by shortening the conduit 36, the phase position of the current to the dipole 28 is made equal to +A, and the phase position of the current to the dipole 30 is madeequal to A by prolongation of the conduit 38.

The dipoles 47-52 (FIGURE 6), are symmetrically arranged and consequently transmit a signal through the supplementary lobe 13. This can be the same as the signal through the dipoles 23-33, but as a rule, it is advantageous to provide a separate modulator and tone mechanism, corresponding to the modulator and the tone mechanism 16 for transmission through the-dipole system 47 52. Then it is possible simultaneously to transmit a given bearing indication through the one lobe 13, for in stance from the dipole system 28453, and an indication of the contra bearing through the other lobe 13, in this case through the dipole system 4752.

In this case, the dipoles 53-58 together form something corresponding to the antenna 19 in FIGURE 1. Regarding to begin with only the antenna dipoles 54 and 57, these may be considered equivalent to the dipoles of the antenna 19. In the field direction 59, corresponding to the axial direction of the field lobes 20, the radiation from the displaced dipoles 53 and 55 or 56 and 58, respectively, will support the radiation from middle dipoles 54 and 57, whereas the dissymmetry radiation in a direction perpendicular to the field direction 59 from the antenna 53 is compensated for by the radiation from the antenna 55 turned in the same direction. The corresponding will also have validity for the radiation from the antennas 56 and 58. One will therefore obtain a radiation diagram from the antennas 53-58 which, with wholly allowable accuracy, will adapt itself to the radiation diagram 20, FIGURE 1. The coupling to the antenna dipoles 53-58 will be evident from FIGURE 5. As a rule it is not required to make any separate compensation of the lengths of the feeder lines to the dipole antennas, but these feeder lines should simply mutually be of equal length. The connection point 66 is connected to the modulator and tone mechanism 21 by means of the commutator 18.

Practical tests have proved that a given length of the reflector bars is required in order to obtain a good screening action. Each dipole bar should, in the usual way, be of a length of 1/4, and the inward-turned ends should be rather close to each other, supported by a common insulator, and therefore the combined length will, as shown in FIGURE 3, be \/2. The reflector bars should not be less than %)t in length. The distance between each dipole element and the corresponding reflector element in radial direction should further be -)\/4. In all of the above given dimension statements, A, as usual, indicates the wave length of the oscillation for which the antenna system is tuned.

When the commutator, connected to the antenna system according to the invention, is placed into rotation, a successive switching will take place. Next after the described state, a state will occur in which the bearing indicating signal is connected to the antennas 29, 30, 31, 32, 33, and 56, and on the other side to the antennas 51, 50, 49, 48, 47 and 55, respectively. Simultaneously, the covering field signal is connected to the dipole antennas 54, 53 and 28 or 57, 58 and 52, respectively.

The total picture of all of the field diagrams has turned one angular step in a clockwise direction. It the total number of dipole elements is eighteen, as shown in the figures, this will correspond a turning of the field diagram picture by 20. If the total number of dipole elements should instead be 27, the turning would be 15, and with 36 dipole elements one would obtain a turning for each step of only FIGURE 6 shows a diagram for the characteristics in an antenna system according to the invention at standstill. The dipoles have the same reference numerals as in FIGURES 2, 4 and 5. The characteristics of the bearing indicating field are drawn with heavy dash-lines, whereas the characteristics of the covering field are drawn by light dash-lines. One can see due to the spacings between the dipole units, there occur in the way well known to the man skilled in the art, side lobes in connection with the characteristics of the bearing indicating field.

In FIGURE 6, the motor 62 drives the three sound mechanisms 16' and 16", corresponding to the sound mechanism 16 of FIGURE 1, and also the sound mechanism 21, corresponding to the sound mechanism 21 of FIGURE 1. These three sound mechanisms are fed from the radio frequency generator 17, which also corresponds to the radio frequency generator 17 in FIGURE 1.

The dash-dotted lines are shown as the shaft 61 from the motor 62 to the dilferent sound mechanisms. In the conduits between the different sound mechanisms 16, 16" and 21, on the one side, and the antenna systems belonging thereto, on the other side, a commutator device 82, 83, 84 is shown and corresponds to the commutator 18 of FIGURE 1, but it is not made in the same way as described in connection with FIGURES 3, 4 and 5, but instead it is constructed the way shown in FIGURE 7 by 67.

The connection between the modulator 16 and the dipole units 28-33 or the dipole units entering in their place during the rotation of a commutator 67, is evident from FIGURE 7. The commutator is arranged on a shaft 61 driven by a motor 62 by means of a cog-gear 63 with a gearing relation adapted in such a way that the tone mechanism will, at the correct moment, create the bearing indicating statements. The conductor 64 is connected to the modulator 16. It is made in the form of a coaxial cable and over a pair of baluns 65, 66 for change to parallel conductor relation connected to the stator portion of the capacitive commutator 67 of a kind well known per se. The rotor portion of the commutator is connected to a pair of baluns 68, 69 for changing the conductors into coaxial relation, in which state they are carried on along the antenna pole to distributors 78, 79 for connection to the difierent dipole elements. The commutator is made as a qu-arter-wave-length coupling, the conduits of each from the baluns 68 and 69 being over collector points 70, 71 and equalization lines 72, 73, 74 as well as 75, 76, 77, respectively, connected to primary bars of a quarter of a wavelength, said bars being grounded at their end turned away from the voltage connection. In parallel with these bars, the primary bars, secondary bars are arranged which are also of a quarter of a wavelength. The primary bars are mounted on an insulating base connected to the shaft 61 so that it will rotate together with this shaft, the secondary bars being fixed and connected to the dipole elements by means of baluns. For instance, the conductor 72 is over a primary bar 78 coupled to a secondary bar 79, said bar being by means of the conductor 80 and the balun 81 connected to the dipole element 28.

The invention is, of course, not limited to the above described arrangement, also shown in the figures, but different modifications may occur within the scope of the invention.

What is claimed is:

1. A speakingradio beacon comprising a first signal source for transmitting signals for the indication of a bearing, and a second signal source for creating a covering signal, an antenna system having a first radiation pattern in the shape of two sharply defined opposed beams and a second radiation pattern in the shape of a figure 8 with the am's thereof perpendicular to the aXis of said beam, said antenna system including a plurality of dipoles arranged at equal distances around a circle, a corresponding circle of reflector bars disposed inside said circle of dipoles, and a rotating commutator, having a stator and a rotor portion, said stator portion connected to said dipoles and two mutually opposite groups of said rotor portion connected to said first signal source and two intermediate groups of said rotor portion connected to said second signal source, whereby when some of said dipoles are transmitting signals for the bearing indication within said first radiation pattern the remainder of said dipoles are transmitting said covering signal within said second radiation pattern.

2. A speaking radio beacon according to claim 1, wherein said commutator comprises a plurality of quarter-wave-length couplings with their primary sides connected to said signal source and their secondary sides connected to said dipoles.

3. A speaking radio beacon according to claim 2 wherein said couplings are connected to a plurality of common collector points by means of intermediate conductors having a length adapted to compensate for the distance between each dipole and a mean level for all of said dipoles acting in parallel.

4. A speaking radio beacon according to claim 1 wherein the number of dipoles is a multiple of 9, one third of said dipoles being connected to a first transmitter for creating a first bearing identification signal, a diametrically opposite group of one third of said dipoles being connected to a second transmitter for creating a second bearing identification signal, and the remainder of said dipoles being connected to a third transmitter for creating a covering field in the shape of the second radiation pattern.

References Cited in the file of this patent UNITED STATES PATENTS 2,188,649 Carter Jan. 30, 1940 2,407,169 Loughren Sept. 3, 1946 2,432,134 Bagnall Dec. 9, 1947 2,432,777 Luck Dec. 16, 1947 2,466,354 Bagnall Apr. 5, 1949 ,0 8 Granqvist May 15, 1956 2,804,615 Wei'he Aug. 27, 1957

Claims (1)

1. A SPEAKING RADIO BEACON COMPRISING A FIRST SIGNAL SOURCE FOR TRANSMITTING SIGNALS FOR THE INDICATION OF A BEARING, AND A SECOND SIGNAL SOURCE FOR CREATING A COVERING SIGNAL, AN ANTENNA SYSTEM HAVING A FIRST RADIATION PATTERN IN THE SHAPE OF TWO SHARPLY DEFINED OPPOSED BEAMS AND A SECOND RADIATION PATTERN IN THE SHAPE OF A FIGURE 8 WITH THE AXIS THEREOF PERPENDICULAR TO THE AXIS OF SAID BEAM, SAID ANTENNA SYSTEM INCLUDING A PLURALITY OF DIPOLES ARRANGED AT EQUAL DISTANCES AROUND A CIRCLE, A CORRESPONDING CIRCLE OF REFLECTOR BARS DISPOSED INSIDE SAID CIRCLE OF DIPOLES, AND A ROTATING COMMUTATOR, HAVING A STATOR AND A ROTOR PORTION, SAID STATOR PORTION CONNECTED TO SAID DIPOLES AND TWO MUTUALLY OPPOSITE GROUPS OF SAID ROTOR PORTION CONNECTED TO SAID FIRST SIGNAL SOURCE AND TWO INTERMEDIATE GROUPS OF SAID ROTOR PORTION CONNECTED TO SAID SECOND SIGNAL SOURCE, WHEREBY WHEN SOME OF SAID DIPOLES ARE TRANSMITTING SIGNALS FOR THE BEARING INDICATION WITHIN SAID FIRST RADIATION PATTERN THE REMAINDER OF SAID DIPOLES ARE TRANSMITTING SAID COVERING SIGNAL WITHIN SAID SECOND RADIATION PATTERN.

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