US2383415A

US2383415A - Loop antenna apparatus

Info

Publication number: US2383415A
Application number: US478748A
Authority: US
Inventors: Wladimir J Polydoroff
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-03-11
Filing date: 1943-03-11
Publication date: 1945-08-21
Anticipated expiration: 1962-08-21

Description

Aug. 21, 1945.

` w. J. PoLYDoRoFF LOOP ANTENNA ABPARA'iUs Filed March 11. 1.943 2 sheets-sheet 1 .IIIIIIIIII llll Aug. 21, 1945. w. J.- PoLYDoRoFF y 2,383,415

`LoP ANTENNA AFPA-@Tris l v Filed Maren l11', l1945 '2 sheets-sheet 2 to provide antenna construction comprising a plu- Patented Aug. 21, 1945 UNITED STATES lPATENT OFFICE LOOP ANTENNA APPARATUS `Wladimir J. Polydoroff, Wilmette, Ill. Application March 11, 1943, Serial No. 478,748

6 Claims. (Cl. Z50-33) The invention relates to directional loop antennae and has more particular reference to improvements in the construction and operation of antennae of this character for improving reception over a wide range of frequencies.

In my Patent No. 2,354,332, granted July 25, 1944, I disclose a loop antenna having coil windings in associated relation `with an elongated core in the form of a long cylinder composed of finely divided iron particles. greatest use of the iron, the coils as disclosed in said application have the maximum number of turns in close association with the iron and said coil windings are spread throughout substantial- I ly the length of the elongated core. i"

An object of Vthe present invention is to improved loop antennae of this character and thereby materially increase their efiiciency in the reception of radio waves. v

Another object of the present invention is to f' provide an 'improved construction of directional loop antennae for use as low impedance loops. An important advantage of this type of antenna is due to the fact that when a small inductance l..

loop is fed into a receiver through a suitable input transformer a large range of frequencies can be covered. It has been possible to employ such low impedance antennae to cover the frequency range from approximately 100 to 1500 kilocycles.

However, if itis desired to cover a larger frequency range another such antenna must be employed of either more or less inductance, which second antenna is switched on for the corresponding extended frequency range. tennae are used in close vicinity to `each other it has been found thatY the presence of an idle loop in the I'leld of an active one causes absorption of the energy from the said active loop, re.. sulting in considerablel weakening of the signal. Also the use of two coils in close association with each other will produce deflection of the signal from its true direction, which effect is known as deviation.

Another object of the invention, therefore, is

rality of loop windings and which antenna construction will receive radio Waves of high and low frequencies andwherein the absorption loss and antennae loops so that they may be continuously rotated and maintained at right angles with respect to each other or at any desired angular relation.

The employment of ktwo loop antennae mounted for synchronous rotation as above described increases the weight and bulk of the system.

\ Therefore another object of the invention is to In order to make the l(lo If two such anl the deviation effect above described is substantially eliminated.`

It has been customary to mount each antenna loop to permit rotation of the same in order that its directional properties may be fully utilized. In this connection, a further object of the invention is to provide apparatus for mounting two 55 advantageously use such antenna loops in a common structure so as to provide apparatus of small physical dimensions and which can be operated in a manner whereby the undesirable absorption effects and deviation are eliminated and reception over a wide range of frequencies is made possible.

With these and various other yobjects in view the invention may consist of certain novel features of construction and operation as will be more fully described and particularly pointed out in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention and wherein like reference characters are used to designate like parts- Figure l. is a vertical sectional view illustrating improved apparatus coming within the invention for mounting antenna loops to eliminate undesirable absorption and deviation effects;

Figure 2 is an elevational view illustrating a parallel position of the loops which permits assembly of the streamlined cover;

Figure 3 is a sectional View showing a modiiication of the invention wherein two loop windings are mounted in close associated relation on a single iron core member; and

Figure 4 is a wiring diagram showing a method whereby said loop windings on the common core member may be electrically connected in parallel by remote control.

Figures 5 and 6 are elevational and end views, respectively, showing a preferred manner of electrostatically shielding the antenna loops; and

Figure 'l is a vertical sectional view through loop antenna structure such as employed in Figure l.

Referring more particularly to Figure 1, the apparatus disclosed includes two separate and independent loop antennae suitably mounted for synchronous rotation with means being provided whereby the loops are maintained at right angles with each other at'all times. Since the illustrated embodiment is adapted to be attached to the fuselage or similar section of an airplane the numeral-I indicates` the shell of said plane to which the apparatus is suitably fixed by any suitable means. For accommodating the apparatus the shell is provided with an elongated opening II and the apparatus is positioned on the exterior' of the shell with respect to this opening so that proper access may be had to the interior of the apparatus and so that the operating instrumentalities may project therefrom to within the airplane.

The direction finding elements of the present apparatus are indicated in their entirety by numerals I2 and I3. These comprise loop antennae which may be constructed in accordance with the disclosure of my Patent No. 2,354,332 herein iden- CTI titled, Figure 7 illustrating one of the several modifications of loop antenna structure shown in said patent. It will be understood that veach'loop antenna may therefore include an elongated iron core 8 preferably of finely divided iron particles having coils 9 in close association with the core. The coils are carried by an insulating tube I9 which encloses the ferromagnetic core. In this modification the coils El are wound in opposite directions and are connected in parallel to the conductors 39 which extend through the support I5 and electrically connect with collector rings 3S, as will be fully understood as the description pro- Cedcs. Each coil and core combination is suitably encased within a cylindrical housing I 4 which is carried by a support I5. Each end of the housing is closed by a disc I6 held in place by means of the elongated bolt Il' extending, longitudinally through the iron core and receiving the threaded nut I 8. It will be observed that each loop antenna has a right angled relation with its associated loop antenna. This is clearly illustrated in Figure 1. In accordance with the invention this ninety degree relation of the loops with each other is maintained at all times even though the loops are mounted for rotation in order to more fully realize their directional properties.

The base member of the present apparatus is indicated by numeral 20, the same having a relatively narrow peripheral top surface 2I which is flat throughout its extent for receiving the streamlined cover 22 of the device. Said cover is preferably formed of a transparent plastic or other suitable material and the same is streamlined, having a shape closely approximating that of a bullet to materially reduce air resistance. Said cover is thus provided with a pointed nose 23 and a rounded end 24. A plurality of screws 25 are adapted to fit within the recesses 26 formed in the base member 2D to securely and releasably hold the streamlined cover to the base.

lThe support I of each loop antenna is recessed for receiving a shaft by means of which the loop antenna is journaled for rotation. The loop antenna indicated by numeral I2 is xed to shaft 2l in this manner, the parts being held in proper assembled relation by the screws 28. Also loop antenna I3 is fixed to shaft 29 with the parts being secured together by the screws 3D. The shafts pass through the partition 3I to depend below the same and extend into a recess provided therefor in the bottom wall 32 of the base member. The partition and bottom wall therefore provide the necessary journalling means for each shaft. The shafts are equipped with similar gears 33 and 34, respectively, preferably of the split type, to provide tension for eliminating back lash. Each gear is Xed to its shaft by means of the set screw 35. The shafts are hollow to permit the passage of wires from the windings and below the gear each shaft is provided with an insulating sleeve having collector rings 36, the said rings for shaft 21 being indicated by numeral 36 and the rings for shaft 29 being indicated by numeral 3l, to which rings the wires from the windings are soldered. A brush 38 is maintained in contact with each collector ring and the brushes for the rings 35 are suitably supported by the upright 40, whereas, the brushes for the collector rings 31 are fixed to the upright 4 I. By means of suitable wires provided by the cable 42 the brushes are electrically connected to apparatus inside the airplane and the electrical circuit is therefore completed by said brushes through the collector rings to the respective loop windings of the antennae I2 and I3.

l The opening II in the shell of the airplane is made large enough to permit the member 43 to pass through the same for securement to the bottom Wall 32 of the base. The screws 44 are employed to releasably secure said member in place. The member provides a suitable opening so that cable 42 may extend through the same into the interior of the apparatus which is necessary since the individual wires of the cable have electrical connection with the brushes 38. The member 43 also provides the boss 45 which journals the main shaft 46 of the apparatus and also the actuating shaft 41 adapted to have interlocking engagement with shaft 46 by means of which the same is rotated. The main gear 48 is fixedI to shaft 45 and said gear in turn meshes with the split gears 33 and 34. Rotation of the main gear therefore simultaneously rotates the split gears and their corresponding shafts. The antenna loops I2 and I3 are synchronously rotated and therefore the angular relation which one loop has with its companion loop is maintained at all times.

The loop I2 may be considered as having high inductance and loop I3 may be'considered as having 10W inductance. Therefore in operation of the present apparatus the loop I2 will be placed in operation when it is desired to pick up radio waves of low frequency and loop I3 Will be placed in operation when it is desired to pick up high frequency radio waves. When one loop winding is in operation the other loop winding is idle. When two such loop antennae loops in close association with each other are operated in this manner the presence of an idle loop inthe field of an active one results in absorption of the energy from the said active loop, which results in weakening of the signal and is therefore undesirable. In the apparatus of the invention this absorption loss is substantially eliminated by placing one loop antenna at right angles to its companion loop and in maintaining this relationship while providing for free rotation of the loops.

The split gears 33 and 34 can be easily assembled on their respective shafts since the operator has access to the interior of the base member 29 when the member 43 is removed. The uprights `40 and 4I and the brushes are xed to said member so that these elements in addition to the cable and the boss 45 constitute a unit. In assembling the streamlined cover it is necessary to place the loops I2 and I3 in parallel alignment, as shown in Figure 2. Only when both loops are thus aligned is'it possible to place the elongated cover over the same. To rotate loop I3 by hand and at the same time prevent loop I2 from rotating it becomes necessary to loosen the split gear 34 to disconnect said gear from shaft 29. Ihe geared relation which the two shafts have with each other is thereby disconnected so that shaft 29 and the loop antenna I3 xed thereto can be independently rotated into a longitudinal direction similar to that occupied by loop I2. The invention provides an opening 50 in the base member 29 which is aligned with the split gear 34 so that the operator can insert a screw driver or other instrument through said opening 50 and release the connection which this gear has with shaft 29.

Normally said opening D is maintained closed by means of the screw 5I. It is necessary to proceed as above indicated each time it is desired to remove the streamlined cover from the apparatus or replace said cover.

With the streamlined cover in place the split gear 34 is again secured toits shaft 29 and the geared relation between the two loops I2 and I3 is the same as before, with the result that the loops are simultaneously rotated by the actuating shaft 41 while desired angular relation between loops isl maintained. The fact that loop antenna I3 can be released from its split gear 34 renders it possible to connect the loops through the gears in any desired angular relation from a ninety degrec relation of the magnetic axes of the loops to a parallel alignment, as shown in Figure 2.

In Figure 3 a modification of the invention is disclosed wherein a low inductance loop winding and a high inductance loop winding are both wound on the same core. Winding the two loops on a common core has the advantage that the total weight and bulk of the system is materially reduced.

Referring to said ligure, the elongated core indicated by numeral 4lill is composed of finely divided iron particles. Since an iron core is used the effective permeability is increased. A form or shell 6I of insulating material is placed over the iron core, the same having a close fit therewith and providing a plurality of recesses extending completely around the cylindrical shell for receiving the wire comprising the respective windings. The shaft 62 extends into the co-re 60 substantially centrally thereof and said shaft may be suitably journalled to provide for rotation of the core. The two coils 63, located in the outside recesses provided by the insulating shell 5I', cornprise a plurality of turns of relatively fine wire. The coils are connected by conductor B4 and therefore they constitute the loop of high inductance indicated by numeral 65 which is employed for the reception of radio waves of lo-w frequency. 'Ihe conductor 84 is provided with a center tap which is grounded at 66. The inside recesses pro- 7 vided by the shell 6 Icontain a less number of turns of heavy Wire to form coils B1 which therefore have low inductance and comprise the loopindicated by numeral 88 for receiving radio waves of high frequency. The conductor 69 connects the two coils -61 and said conductor is provided'with a center tap grounded at 10.

In this modication of the invention the coils 63 comprise the loop 85 of high inductance and coils 81 comprise the loop 68 of low inductance. Both are wound on the same iron core to save weight and reduce the bulk of the system. However, the loops are coaxial to each other and they are therefore subject to absorption and deviation, as previously explained in connection with Figure l. In accordance with the invention these undesirable eiects are substantially eliminated by the provision of means for electrically connecting the high inductance loop G5 in parallel withthe low inductance loop 88 during the operation of said low inductance loop. As a result the inductance of loop 58 is somewhat reduced but this can be compensated for by initially adding a few eX- tra turnsof wire to coils 61.

To accomplish the electrical connection of the loops for thepurpose above described, the invention provides a plurality of collector rings indicated by numerals] I, 12, 13, 14 and 15. The collector rings are suitably fixed to rotate with shaft 82,' being insulated therefrom by means of the lsleeve 16 of insulating material.

ring has contact with a metal brush 11 collectively double'pole single throw switch 84. In a similar Imanner the coils 53A are electrically connected by

conductors

85 and 86 with the collector rings 14 and 15 respectively. Likewise the circuit is continued by the brushes 11 in contact with these collector rings and .by the conductors 81 and 88 to the switch 84 previously mentioned. The conductors 99 and 9| constitute the conductors enclosed within cable 92 which extends to within the airplane or other enclosure on which the present apparatus is mounted. The center collector ring '13 is suitably grounded at 93 and this collector yring through its corresponding brush 11 is connected by conductor 94 to the sheath of the cable.

During operation of the apparatus as disclosed in Figure 3 it will be understood that switch 84 Awill be in open position fo-r the reception of radio waves in the low frequency range since these frequencies are picked up by the windings 63 comprising the loop 65 of high inductance. This loop `is electrically connected at all times to the collector rings 14 and-15 which in turn have connectio-n with the conductorsfrom cable 92. Therefore when this loop 65 is in operation it will be understood that the switch 84 is open and loop BB remains idle. However, in accordance with lthe invention the high frequency low inductance `loop 88 is always operated in parallel with the low `frequency high inductance loop 65. Loop 68 hav- -ing connection with -only be 'connected to conductors 90 and 9| of the cable 92 by closing the switch 84. Closing of said vswitchY automatically connects the loop 65 in parcollector rings 1I andy 12 can allel` therewith.

Figure 4 discloses apparatus whereby the loops may be connected in parallel as above described by remote control. In place of the double pole single throw switch a contactor 95 is provided which, as shown insaid figure, is normally inoperative. Therefore the conductors 82 and 83v are normally disconnected from the conductors 81 and 88. The contactor is actuated by means of the vsolenoid 9B having electrical connection through switch 91 with a source of current 98. When switch 91 is closed the solenoid 98 is energized and contactor 95 is caused to descend into its operative position. The contactor will therefore close `the circuit to the

conductors

82 and 83 leading to the coils comprising the loop 68 and the said loop is thus placed in operation, being automatically connected in parallel with the coils comprising aloop 65. Therefore whenever the high frequency loop is used it is in parallel with the idle low frequency loop. For best results the above described switch structure should be placed as close to the connector rings as possible.

In direction finding loops the direction of the transmitter is indicated by a sharp zero signal when the loop axis points toward the transmitter. In order to obtain sharp directional bearings only the electromagnetic component of the radio wave Each collector shculd act on the loop, the electrostatic component being suppressed by electrostatic shielding of the windings. Preferred structure for carrying out the above is shown in Figures 5 and 6 wherein the loop antenna is enclosed by special cloth into which metal wires are woven in one direction. After the coils are placed in the insulating form 6I another insulating tube is placed over the windings in order to protect them from the atmosphere, said tube being indicated in Figure 5 by numeral I 00. The cloth having the wires IUI is then placed around the exterior surface of the tube 00 and in accordance with the invention the cloth is provided with a gap |02 so that the wires extending in the same direction circumferentially of the loop antenna are not joined but are left open circuited at the top. However, all the wires are electrically connected in the vicinity of the lower portion of the casing and the same is grounded at l 03. Each loop antenna is also closed at its respective ends by the disc I 04 which is covered with cloth providing the vertically disposed wires |05. These wires are also electrically connected at their lower ends and which connection is suitably grounded at |06.

An electrostatic shield may also be made from thin metal foil or metal leaf, preferably metal such as copper, which is a good conductor of electricity. A gap is provided so that the metal foil does not extend completely around the loop antenna and also in a manner as disclosed the various parts of the metal shield are grounded.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated by the drawings, as various other forms of the device will of course be apparent to those skilled in the art Without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. An antenna system for the reception of radio waves, said system including a loop antenna of high inductance for receiving radio waves of low frequency, a second loop antenna of low inductance for the reception of radio Waves of high frequency, each loop antenna comprising a pair of coils coaxially wound on an elongated core member, a shaft journalling each said loop antenna for rotation on an axis normal to its magnetic axis, a gear on each shaft, releasable means securing one of said gears to its shaft whereby the shaft may be independently rotated when the gear is released, and a driving gear having meshing relation with the gears fixed to the shafts respectively, said geared connection of the loops being constructed and arranged to provide for rotation of the loops simultaneously While maintaining their magnetic axes at right angles to each other.

2. An antenna system for the reception of radio waves, said system including two loops spaced a distance laterally of each other and adapted to rotate in unison, each loop comprising an iron core having at least one coil coaxially wound on the core and in close association therewith, a shaft supporting each loop and journalling its loop for rotation on an axis normal to the magnetic axis of the loop, a driving member fixed to each shaft, and actuating means for rotating the driving members simultaneously and to a like extent, whereby both loops are rotated at the same time and whereby any preset relation between the magnetic axes of the loop is maintained.

3. An antenna system for the reception of radio waves, said system including two loops spaced a distance laterally of each other and adapted to rotate in unison, each loop comprising an elongated iron core having at least one coil coaxially wound on the core andin close association therewith, a shaft supporting each loop and journalling its loop for rotation on an axis normal to the magnetic axis of the loop, a driving gear fixed to each shaft, releasable means securing one of said gears to its shaft whereby the loop supported by said shaft may be rotated independently when the gear is released, and an actuating gear for rotating the driving gears simultaneously and to a like extent, whereby both loops are rotated at the same time and whereby any preset angular relation between the magnetic axis of the loops is maintained.

4. An antenna system for the reception of radio waves, in combination, an elongated streamlined housing having an opening in the wall thereof intermediate the ends of the housing, supporting means for said elongated housing having secured relation with the Wall defining said opening in the housing, at least two loop antennae having location within the streamlined housing and spaced along the longitudinal axis of said housing, each loop comprising an iron core having at least one coil coaxially wound on the core and in close association therewith, a shaft supporting each loop and journalling its loop for rotation on an axis normal to the magnetic axis of the loop and also normal to the longitudinal axis of said housing, a driving member xed to each shaft, and actuating means for rotating the driving members simultaneously and to a like extent.

5. An antenna system for the reception of radio waves, in combination, an elongated streamlined housing having an opening in the wall thereof intermediate the ends of the housing, supporting means for said elongated housing having secured relation with the Wall dening said opening in the housing, at least two loop antennae having location within the streamlined housing and spaced along the longitudinal axis of said housing, a shaft supporting each loop and journalling its loop for rotation on an axis normal to the magnetic axis of the loop and also normal to the longitudinal axis of said housing, a driving member fixed to each shaft, and actuating means for rotating the driving members simultaneously and to a like extent.

6. An antenna system for the reception of radio waves as dened by claim 4, wherein the supporting means for the elongated housing additionally supports the shafts for the loops in a manner permitting rotation of the same.

WLADIMIR J. POLYDOROFF.