452,791

PATENT SPECIFICATION

Application Date: Feb. 28, 1935. No. 6403/35.

Complete Specification Left: Feb. 5, 1936.

Complete Specification Accepted: Aug. 28, 1936.

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PROVISIONAL SPECIFICATION

Improvements in or relating to Directional Wireless Aerial Systems

I, ALAN DOWER BLUMLEIN, a British Subject, of 32, Audley Road, Ealing, London, W.5, do hereby declare the nature of this invention to be as follows:-

The present invention relates to directional wireless aerial systems such as can be used either for transmission or reception of electromagnetic waves.

One array of known type comprises a series of half wave aerial elements arranged in line one above the other. The top of each half wave element is joined to the bottom of the half wave element above it by a half wave auxiliary element, the half wave auxiliary elements being folded either so as to neutralise their radiation, or to ensure that their radiation adds to that of the straight half wave aerial elements. When this type of array is fed at one end, say the lower end, the radiation from the lower elements seriously attenuates the currents flowing to the upper elements, so that the upper elements are not fully effective in radiating as desired. Similar troubles are experienced with other types of aerial array where the power for one radiating element is fed through other radiating elements.

It is an object of the present invention to eliminate or reduce this difficulty.

According to this invention an aerial array comprises two or more radiating or receiving elements at least one of which is composite and has at least two conductors which are adapted to operate as a feeder for another radiating or receiving element having two or more conductors, one of which is arranged as a partial or complete shield for another of said conductors, two or more of said conductors including said shield being adapted to operate as a feeder for a further radiating or receiving element of the array.

The conductor which is arranged as a shield may be in the form of a conducting tube which surrounds another conductor and is insulated therefrom.

Alternatively the shield may comprise a group of conductors located around a central conductor or group of conductors.

The invention will now be described with particular reference to transmitting aerial arrays, but it is to be understood that the systems discussed are also applicable to reception. The phasing of an aerial array is most simply considered by treating it as a transmitting array and adjusting the lengths of the elements and the phasing connections so as to obtain correct currents in and voltages on the elements: the array so designed may the be used as a receiving array by replacing the generator by a suitable receiver.

An aerial array according to the invention may comprise five lengths of copper tube, each equal in length to have a wavelength of the waves to be transmitted, arranged in a line one above the other, giving a total length of 2½ wave lengths, there being short insulating gaps between the consecutive tubes. Each tube contains a central conductor insulated from it, thus forming a length of concentric feeder of known type. At each gap the inner conductor of the lower element is joined to the outer tube of the element above, and similarly, the inner conductor of the upper element is joined to the outer tube of the element below it. The combined arrangement forms a total of 2½ wavelengths of feeder in which the inner and outer conductors interchange each half wave length. The interchange may be effected by inserting an insulator between adjacent tubes, the insulator having a number of slots through which the inner conductor may be brought out by a plurality of copper strips, and joined to the appropriate outer tube. Alternatively the ends of the adjacent elements may not be in quite the same line, thus facilitating a cross connection between the inner conductor of one and the outer conductor of the other. The whole array may be fed by connecting a concentric or balanced feeder to the inner and outer conductors of the bottom radiating element. If a concentric feeder is used, the inner conductor of the feeder may be connected to the outer tube of the bottom element and the outside of the feeder to the inner conductor of the bottom element.

The feeder has preferably a quarter wave conductor joined to it at one quarter wavelength from its junction with the aerial, and arranged to extend, substantially parallel to the feeder towards the aerial, the free end of the quarter wave conductor being thus adjacent the bottom of the aerial. Further, if this quarter wave conductor be made of the same outside dimension as the feeder, the end of the quarter wave conductor adjacent the aerial is advantageously connected to the inner conductor of the feeder. Also the length of this quarter wave element may be altered from an exact quarter wave length in order to tune the aerial. The use of an auxiliary quarter wave conductor serves to render the aerial end of the feeder substantially symmetrical and to prevent distortion of the polar diagram of the array by currents flowing on the outside of the sheath of the feeder. Arrangements of this kind are described in co-pending application No. 22023/34 which is cognate with application No. 5102/34.

The feeder may be matched to the aerial by a suitable transformer, for example by making the inner conductor of the quarter wavelength of the feeder adjacent the aerial of such as size that this quarter wavelength of feeder operates as a quarter wave transformer in known manner.

In the aerial described above, the inner conductor may obviously be omitted from the top element as it serves no useful purpose. Although described for five elements, this type of aerial may be used for nay number of elements from two upwards.

The elements need not necessarily be arranged in a vertical line, but can be arranged, say, horizontally, to give a horizontally polarised radiation. Such an array may be fed from one end, or from some point along its length. A voltage feed may be applied by connecting a feeder to adjacent ends of outer tubes of adjacent elements, or a current feed may be introduced by breaking the inner or outer conductor at the centre of an element and connecting the ends so formed to the two conductors of a feeder.

The elements need not necessarily be arranged in a straight line; some of the elements may extend at a right angle to others, and may if necessary consist of a pair of similar conductors so as to form a non-radiating length of feeder. Similarly aerials of the type described may be used with other groups of elements to form a more complex array.

A modification of the construction above described consists in using elements constructed of several conductors surrounding a central conductor. For example, the vertical array described may consist of elements of four (or more) wires surrounding a central wire, the outer wires acting in parallel form a screen for the inner wire. The outer wires may be held clear of the inner wire by suitable spreaders. At each half wavelength an insulated ring with eight slots may be inserted. The four other wires at the upper end of the lower half wavelength pass through four alternative slots and are then drawn together and joined on to (or form) the central conductor of the upper half wavelength. Similarly the four wires at the lower end of the upper half wave pass through the remaining slots and are drawn in to the inner conductor of the lower half wavelength.

The action of the vertical arrays described above is to radiate most strongly in the horizontal direction. For this requirement it is necessary that all the half wave radiators operate in the same phase, that is, the upper ends of all half waves should be positive together when their lower ends are negative together. Now the upper end of one half wave element is joined through an effective feeder to the bottom of the half wave element next but one above it. Since the feeder length is half a wavelength however, the feeder will produce a reversal of phase thus rendering the top of one element positive at the same time as the bottom of the element next but one above it is rendered negative, and so giving the required phasing. Owing to the proximity of the ends of the adjacent aerial elements it may be found necessary to add additional reactances to the aerial in order to tune it to the required frequency.

Other phasings can be arranged by suitable lengths of feeder elements, or the effective feeder length of an element can be increased without increasing its length as a radiator by folding the inner conductor, or by folding both the inner and outer conductors and short circuiting the fold of the outer conductor.

A multi-element tubular array as described, may for short wavelengths be made partially or wholly self-supporting by make the outer tubular members of sufficient diameter and strength. Also this diameter may be reduced for the high members which have less weight to support and are less stressed by wind.

The present invention is not limited to the above-described examples and many modifications within the scope of the invention will be apparent to those versed in the art.

Dated this 25th day of February, 1935.

REDDIE & GROSE,

Agents for the Applicant,

6, Bream’s Buildings, London, E.C.4.

COMPLETE SPECIFICATION

Improvements in and relating to Directional Wireless Aerial Systems

I, ALAN DOWER BLUMLEIN, of 32, Audley Road, Ealing, London, W.5, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:-

The present invention relates to directional wireless aerial systems such as can be used either for transmission or reception of electromagnetic waves.

On aerial system of know type comprises a series of half wave aerial elements arranged in line one above the other. The top of each half wave element is joined to the bottom of the half wave element above it by a half wave auxiliary element, the half wave auxiliary elements being folded either so as to neutralise their radiation, or to ensure that their radiation adds to that of the straight half wave aerial elements. When this type of aerial system is fed at one end, say the lower end, the radiation from the lower elements seriously attenuates the currents flowing to the upper elements, so that the upper elements are not fully effective in radiating as desired. Similar troubles are experienced with other types of aerial system where the power for one radiating element is fed through other radiation elements.

It is an object of the present invention to eliminate or reduce this difficulty.

According to the invention there is provided a directional aerial system comprising a plurality of elements each having two conductors one surrounding the other, one of the elements being arranged to operate as a feeder for another of the elements, the outer of the two conductors of each element being arranged to radiate or receive more than the inner conductor, and the elements being so connected that when coupled to a suitable transmitter or receiver the currents in all the outer conductors of said elements are substantially in phase with one another.

The outer conductor may be in the form of a conducting tube which surround the other conductor and is insulated therefrom.

Alternatively the outer conductor may comprise a group of conductors located around a central conductor or group of conductors.

According to a further feature of the present invention there is provided a directional aerial system comprising a plurality of radiating or receiving elements arranged end to end, wherein each of said elements comprises an outer conductor surround an inner conductor and wherein the outer conductor of each element is connected to the inner conductor of an adjacent element.

The invention will now be described with particular reference to transmitting aerial systems, but it is to be understood that the systems discussed are also applicable to reception. The phasing of an aerial system is most simply considered by treating it as a transmitting system and adjusting the lengths of the elements and the phasing connections so as to obtain correct currents in and voltages on the elements: the system so designed may then be used as a receiving system by replacing the generator by suitable receiver.

In the accompanying diagrammatic drawing:-

Fig. 1 shows an aerial system according to the present invention,

Figs. 2 and 4 show portions of modifications of Fig. 1.

Referring to Fig. 1 of the drawing, an aerial system comprises five lengths 1, 2, 3, 4, 5 of copper tube, each substantially equal in electrical length to half a wavelength of the waves to be transmitted, arranged in a line one above the other, giving a total electrical length of about 2½ wavelengths, there being short insulating gaps between the consecutive tubes. The tubes 1, 2, 3, 4, 5 contain central conductors 11, 21, 31, 41, 51 insulated from them, thus forming five lengths of concentric feeder of known type. At each gap the inner conductor of the lower element is joined to the outer tube of the element above, and similarly, the inner conductor of the upper element is joined to the outer tube of the element below it. Thus, for example, the upper end 6 of inner conductor 11 is connected to the lower end 7 of outer conductor 2 and the lower end 8 of inner conductor 21 is connected to the upper end 9 of outer conductor 11. The combined arrangement forms a total of 2½ wavelengths of feeder in which the inner and outer conductors interchange each half wavelength. The interchange may be effected by inserting an insulator of the type shown in Fig. 2 between adjacent tubes.

The insulator is in the form of a solid cylinder and has a plurality of slots radiating from the centre 10 of its lower surface to points 11 on the periphery of its upper surface. Through these slots are passed copper strips 12 which are joined together and to the upper end of a central conductor 13 at point 10 and to the lower end of an outer conductor (not shown) at points 11. A similar plurality of slots accommodate strips 14 for connecting the lower end of central conductor 15 to the upper end of the outer conductor (not shown) surrounding inner conductor 13.

Fig.3 shows a modification of a part of Fig. 1. It will be seen that by slightly displacing alternative elements the connections 6, 7 and 8, 9 may be shortened and more easily held spaced apart from one another.

The whole system may be fed by connecting a concentric or balanced feeder to the inner and outer conductors of the bottom radiating element 1, 11. If, as shown in Fig. 1 a concentric feeder 16 is used, the inner conductor 17 of the feeder may be connected to the outer tube 1 of the bottom element and the sheath 18 of the feeder to the inner conductor 11 of the bottom element.

The feeder has preferably an auxiliary quarter wave conductor 19 joined to it as one quarter wavelength from its junction with the aerial, and arranged to extend, substantially parallel to the feeder towards the aerial, the feed end 20 of the quarter wave conductor 19 being thus adjacent the bottom of the aerial. Further, if this quarter wave conductor be made of the same outside dimension as the feeder as shown, the end 20 of the quarter wave conductor adjacent the aerial is advantageously connected to the end 21 of the inner conductor 17 of the feeder. Also the length of the quarter wave element 19 may be altered from an exact quarter wavelength in order to tune the aerial. The use of the auxiliary quarter wave conductor 20 serves to render the aerial end of the feeder 16 substantially symmetrical and to prevent distortion of the polar diagram of the array by currents flowing on the outside of the sheath of the feeder. Arrangements of this kind are described in British Paten Specification No. 438, 506.

In general it is necessary to provide an impedance matching transformer between the feeder and the aerial. In the arrangement shown the transformer is a quarter wave transformer which is constructed by making the quarter wavelength section 22 of the central conductor 17 of suitable diameter different from the diameter of the main part of the central conductor and which operates in known manner. Alternative arrangements by which impedance matching between the feeder and the aerial may be realised are by suitably altering the length of auxiliary conductor 19 and by connecting the aerial to suitable points in auxiliary conductor 19 and sheath 18 other than their ends. Such arrangements are described in co-pending Application No. 25815/35.

In the aerial system described above, the inner conductor 51 may obviously be omitted from the top element 5 as it serves no useful purpose unless a further element is to be connected to the array shown. Although described for five elements, this type of aerial system may be used for any number of elements from two upwards. In each of the elements 1, 11, 2, 21, 3, 31, 4, 41 the outer conductors 1, 2, 3, 4 act as shields for the inner conductors 11, 21, 31, 41 and the outer conductors therefore radiate or receive more than the inner conductors.

The elements need not necessarily be arranged in a vertical line, but can be arranged, say, horizontally, to give a horizontally polarised radiation. Such a system may be fed from one end, or from some point along its length. A voltage feed may be applied by connecting a feeder to adjacent ends of outer tubes of adjacent elements or a current feed may be introduced by breaking the inner or outer conductor at the centre of an element and connecting the ends so formed to the two conductors of a feeder.

The elements need not necessarily be arranged in a straight line; some of the elements may extend at a right angle to others, and may if desired consist of a pair of similar conductors so as to form a non-radiating length of feeder. Similarly aerials of the type described may be used with other groups of elements to form a more complex system.

In another construction shown in Fig. 4, a plurality of wires is employed for each outer conductor. A spreader 23 in the form of a ring is employed at the junction of two elements and is provided with eight slots 24 equally spaced around its periphery. Four wires 25 which form the outer conductor of the lower element pass through four alternate slots and are drawn together to a point 26 where they are joined to the inner conductor 27 of the upper element. The four wires 28 forming the outer conductor of the upper element pass through the remaining slots and are drawn together to a point 29 where they are connected to the inner conductor 30 of the lower element. A similar arrangement may be employed at each junction between two elements.

Instead of connecting the four wires of an outer conductor to a single wire of an inner conductor at points 26 and 29, the four wires may simply be drawn together and themselves constitute the inner conductor. Each outer conductor may be constituted by a suitable number of conductors other than four.

When the systems described above are required to radiate most strongly in the horizontal direction, they are arranged vertically and it is necessary that all the half wave radiators operate in the same phase, that is, the upper ends of all half waves should be positive together when their lower ends are negative together. Now the upper end of one half wave element is joined through an effective feeder to the bottom of the half wave element next but one above it. Since the feeder length is half a wavelength however, the feeder will produce a reversal of phase thus rendering the top of one element positive at the same time as the bottom of the element next but one above it is rendered negative, and so giving the require phasing. Owing to the proximity of the ends of the adjacent aerial elements it may be found necessary to add additional reactances to the aerial in order to tune it to the required frequency.

Other phasings can be arranged by employing suitable lengths of feeder elements, or the effective feeder length of an element can be increased without increasing its length as a radiator by folding the inner conductor, or by folding both the inner and outer conductors and short circuiting the fold of the outer conductor.

In one construction employing tubular outer elements the tubes have a diameter of 4 inches and the inner conductor has a diameter of about ¾ inch in the lowest element 1 decreasing to about ½ inch in the uppermost element 4 or 5. It has been found that the elements operate as half wave elements if their lengths are about 85% of half a wavelength. The capacity at the junctions and the length added by the connections cause the electrical length to be greater than the physical length of the elements themselves.

A multi-element tubular aerial system as described, may for short wavelengths be made partially or wholly self-supporting by making the outer tubular members of sufficient diameter and strength. Also this diameter may be reduced for the higher members which have less weight to support and are less stressed by wind.

The present invention is not limited to the above-described examples and many modifications within the scope of the invention will be apparent to those versed in the art.

Having now particularly described and ascertained the nature of my said inventio9n and in what manner the same is to be performed, I declare that what I claim is:-

  1. A directional aerial system comprising a plurality of elements each having two conductors one surrounding the other, one of the elements being arranged to operate as a feeder for another of the elements, the outer of the two conductors of each element being arranged to radiate or receive more than the inner conductor, and the elements being so connected that when coupled to a suitable transmitter or receiver the currents in all the outer conductors of said elements are substantially in phase with one another.
  2. A direction aerial system wherein said elements are constituted by conductors arranged as concentric feeders.
  3. A modification of the aerial system claimed in claim 1 or 2, in which there are provided two of said elements one of which is an end element and in which the inner conductor of the end element is omitted.
  4. An aerial system according to claim 3, wherein the element other than the end element is constituted by the outer and inner conductors of a concentric feeder, and wherein said end element is constituted by a single conductor or substantially the same size and shape as said outer conductor and is connected at its end adjacent the first named element to said inner conductor.
  5. A directional aerial system comprising a plurality of radiating or receiving elements arranged end to end, wherein each of said elements comprises an outer conductor surrounding an inner conductor and wherein the outer conductor of each element is connected to the inner conductor of an adjacent element.
  6. An aerial system according to any of the preceding claims, wherein the effective electrical length of each of said radiating or receiving elements is substantially one half of the operating wavelength.
  7. A directional aerial system substantially as described with reference to the accompanying drawing.

Dated this 5th day of February, 1936.

REDDIE & GROSE,

Agents for the Applicants,

6, Bream’s Buildings, London, E.C.4.

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Leamington Spa: Printed for His Majesty’s Stationery Office, by the Courier Press. - 1936.