US2526098A

US2526098A - Directive antenna system

Info

Publication number: US2526098A
Application number: US70284A
Authority: US
Inventors: John M Tewksbury
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-01-11
Filing date: 1949-01-11
Publication date: 1950-10-17
Anticipated expiration: 1967-10-17

Description

Oct. 17, 1950 w sBu 2,526,098

DIRECTIVE ANTENNA SYSTEM Filed; m. 11, 1949 In ventor John M. Tewksbury Patented Oct. 17, 1950 UNITED STATES PATENT" orsicsy I 2,526,098. I I g s DIRECTIVE ANTENNA SYSTEM John MrTewksbury, Skowhegan, Maine Application January 11, 1949, Serial No."70,284 5 Claims. (Cl. 250-3351) This invention relates to directive antenna systems and it has particular reference to an antenna obtaining directional effects without the use of reflectors or auxiliary antennae.

In order to obtain directional effects it has been the practice either to use antenna wires which are specially shaped or to utilize standing wave energy produced by a reflector or an auxiliary antenna. All these arrangements require a rather elaborate scheme to be followed when mounting the antenna, as the dimensions of a number of parts, their distance etc., have to be adjusted to the wave length used.

The invention has. for its main object to provide an antenna producing directional effects which are inherent in the unit containing the radiating wire, so that merely the length of the unit has to be selected in accordance with the wave lengthof the waves which are radiated. i

It is a-further object to provide a simple an .tenna system consisting merely of ara'diating' member and a dielectric body surrounding the same.

A further object of the invention consists in providing an antenna system consisting of a radiating wire or tube fitted into a dielectric body which may be either permanently held within said body or which may be inserted into it to form the directive antenna system.

A further object of the invention consists in providing a dielectric body surrounding the radiating antenna wire, producing a directional effect by a varying influence on the radiation in different directions, and adapted to produce a directed wave.

A still further object of the invention consists in providing the radiating antenna wire with a dielectric envelope or sheath adapted to influence the electromagnetic waves radiated withinan arcuate segment in such a way that they are deflected with their direction a of propagation changed by refraction so as to point in a given direction.

} selective or directional effect may be A further object of the invention consists in antenna contained within and surrounded bya dielectric body of substantially cylindrical shape having a biscuit shaped cross section, with a bridge or neck piece containing the antenna wire joining the two enlarged portions of the dielectric body which are positioned on two sides of the antenna wire in order to produce a refraction of the electromagnetic waves emanating from the radiating antenna wire along an arcuate sector, propagation of the waves of said sector being providing a radiating the direction of the changed so as to form a beam with a straight wave front. v g

The principle on which the invention is based consists in providing the radiating antenna wire or "tube with a dielectric body enveloping it and so shaped that the radiation penetrating'said body travels along paths of different lengths, slowing down the velocity of propagation and therefore producing a refraction of different extent in diiferent directions. The shape. of the dielectricsubstance may be so" selected that the resulting wave front is a straight line wherebya produced. The antenna consisting of the antenna wire or tube and the dielectric body may be manufactured as a single be manufactured separately, with a channel provided in it, into which the antenna wire or tube may be inserted.

.The joining of the two members in the last mentioned case is however a simple, mechanical operation not requiring skill or separate calculation or adjustment.

It will also be clear that the dielectric body with or without the antenna Wire embedded into it may bemanufactured in any length, for instance, by extrusion from a nozzle, and may be cut off from a coil or the like at the required length for use in specific cases.

Further more specific objects of the invention will be apparent from the following specification.

The invention is described with reference to the accompanying drawing, illustrating an embodimentby way of example. It is to be understood however that this example serves solely the purpose of explaining the principle of the invention 'and one mode of applying said principle. It will also be understood that'this principle has to be applied individually and that therefore modifications of the shape of the structure and The principle of the invention is best illustrated with reference to Figure 1 which illustrates the unit, or the dielectric body may propagation of waves radiating outwardly from a center 0. With radiation in air the radiation travels at a given time from O to A which distance is equal to that on any other ray OB, OC radiating from 0. Let it now be assumed that the ray OD has to travel through a dielectric in which the velocity of Wave propagation is much smaller than the velocity of propagation in air. In this case, while the rays OB and travel as before and reach points B and C after a given interval, the ray travelling along radius 0A only reaches point D on account of the reduced speed of wave propagation.

If it is further assumed that intermediate rays such as OE are retarded correspondingly by a dielectric offering less resistance than the dielectric along ray OD, it will be clear that in this way a straight wave front instead of a circular wave front will be obtained.

As refraction of the Waves occurs when they travel from a medium of greater density into a medium of less density, the rays OE are also deflected, the angle on of entry between the ray OE and the line P perpendicular to the tangent at the point E being smaller than the angle at which the ray emerges. If the shape of the body of dielectric material surrounding the center of radiation is properly chosen a beam in the direction OD, 0G is radiated, concentrating the rays emanating between the rays OH, 01 in this direction.

The shape of the dielectric body 5 depends on the dielectric constant e on account of the relation 4 t for instance by extrusion in such a manner that the wire I is covered by the body 5, and may be hardened and coiled, the length necessary for an antenna of the desired wave length being cut from the coil. It will be understood that the drawing is on a large scale and that under most conditions the dielectric body is much smaller than shown.

In Figure 4 an antenna is shown consisting of a tubular body 9 such as used for short waves surrounded by the dielectric bodyki. The, tubular antenna may be removable and the dielectric body is manufactured separately in this case, with a cylindrical channel corresponding to the diameter of the tubular antenna. Both pieces are cut to the same length and the tube is then inserted into the channel.

of the electromagnetic Waves in air which'is practically equal to the velocity of light, and e is the dielectric constant of the material used.

Dielectric materials which are practically suitable for the purpose indicated are for instance the plastics; but also other materials, such as glass, porcelain, etc. may be used, although their dielectric constant is lower.

When a body of plastic is used, it may beproduced by extrusion, with the antenna wire 1 already embedded into it. A cross section through an antenna of this type is shown in Figure 3, 5 being ie dielectric body surrounding the antenna wire i which in this example is approximately in the shape of a cylinder, the basis of which is a Boothian or Bernoullian lemniscate.

A special bridge piece or neck portion 8 may be provided in the middle portion of the body surrounding the antennawire i for the purpose of increasing the mechanical resistance of the structure and of joining the two sections or halves of the dielectric body, so that it may be manufactured as a single piece surrounding the wire. On the outside said bridge piece or neck portion may be lined with metal conductors.

The cross section producing the desired directional properties will however differ in shape with every material used and must therefore be calculated separately for each material.

The antenna thus produced, while diffusing some energy 'in the direction perpendicular to the main direction GOD, concentrates the radiation energy emanating along the are 7 defined by the rays I01 and HOH in the direction GOD.

The antenna as will be clear may be produced The invention thus provides a directional antenna of an extremely simple type, the direc tional properties of which are inherent in the antenna itself, so that no further structure such as an auxiliary antenna and no shaping or bending of the antenna is necessary.

When such an antenna is used as a vertical antenna the direction of propagation of the waves is the planepassing through the antenna in the directi-on'GOD. When the antenna is used While in a horizontal position, the. plane GOD must be so positioned as to occupy the angle towards the horizontal at which radiation is intended. If for instance, radiation at. a'certain angle is intended, in order to promote reception by reflection from the upper layers of the atmosphere at a given distance, the antenna or the dielectric r body surrot'inding.v the tube must be adjustedaccordingly. Likewise, if directional reception is intended, the dielectric body must be mounted and turned accordingly; I

It willalso beclearithat :the directive or selective properties ofxthe'antenna arepracticaliy the same whether the antenna is used fortransmiss-ion or forire'ception purposes.

'It will finally .be understood that the shape of the dielectric and other factors which are.vari= able may changeintthe manner required in accordance with the above explained principle of the invention and that changescf other factors which are not essential, such as the, cross sec tion of the antenna Wires may depart from those shown in the drawing without any departure from the essence of the invention.

Having described the invention, claimed as new is:

1. A directional antenna comprising a cylindrical body of plasticswith an antenna wire embedded in the axis of the body along the axis of the cylinder, thegeneratrices of the cylinder being parallel to the antenna wire and the directrix of thelcylin'der being substantially a lemniscate With the antenna Wire positioned at the inter? section of the branches of the 'lemniscate. V

2.- A directional antenna comprising a radiate ing antenna wire, embedded, along its entire length in the center of a dielectric body, said dielectric body being a cylinder, the generatriccs of which .are parallel to;,the antenna wire, while the directrixrunsaiong a curved substantially closed path on each side of the antenna wire, so as to form two substantially closed cylindrical sections, located on the two sides of the antenna Wire, and a cylindrical neck portion between said two substantially closed cylindrical sections, surrounding said antenna-wire.

3. A directional antenna as claimed in claim 1 in which the cylindrical dielectric body is prowhat is the periphery vided with a central channel and in which the antenna wire is formed by a tubular conductor filling the said central channel.

4. A directional antenna comprising a conducting and radiating antenna wire, and a dielectric body arranged in two substantially cylindrical sections on two diametrically opposite sides of said antenna wire, symmetrically with respect to a median plane including the antenna wire and at right angles to the direction of wave propagation, the generatrices of the cylindrical surfaces of the aforesaid sections being parallel to the axis of the antenna wire and the cross section of each cylindrical section at right angles to the last named plane of symmetry increasing in width with its distance from the antenna wire to a maximum and then decreasing,

of each cross section of a, cylindrical section being thus so shaped that the vector drawn from the center of radiation towards points of the periphery of the cross section of a cylindrical section increases with the increase of the vectorial angle between said vector and said median plane.

5. A directional antenna comprising a dielectric body and a conducting and radiating an tenna wire embedded therein, said dielectric body consisting of two substantially cylindrical sections arranged symmetrically on both sides of 6 the antenna wire with the generatrices of the cylinders arranged in substantial parallelism to the antenna wire, each section having a substantially closed curve as a directrix so that its cross section increases to a maximum and then decreases with the distance from the axis of the antenna wire, so that lines drawn from the central axis of the antenna wire toward points of said curved surface of the cylindrical section increase in length with decreasing angle totwo cylindrical sections and including the antenna wire, said increase of length being such that a straight wave form in the main direction of wave propagation is produced.

JOHN M. IEWKSBURY.

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

UNITED STATES PATENTS