US2426632A - Antenna structure - Google Patents

Description

Sept. 2, 1947. N. MARCHAND 2,426,632

ANTENNA STRUCTURE Filed July 22, 1944 Patented Sept. 2, 1%47 ANTENNA STRUCTURE Nathan Marchand, New York, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application July 22, 1944, Serial No, 546,117:

7 Claims.

This invention relates to antenna structures particularly those having directional radiant action characteristics.

An object of the present invention is the provision of an improved antenna structure particularly one having directional radiant action characteristics.

Another object of the present invention is the provision of an antenna structure of the type described which is extremely compact and rugged.

A further object of the present invention is the provision of an improved antenna structure in which the radiating elements include loops formed from concentric line conductors and which depend for their operation on the coupling between the inner conductor and the out side of the outer conductor of said concentric lines provided by gaps in the outer conductor.

Another object of the present invention is the provision of an improved antenna structure employing a plurality of horizontally disposed loops providing plane polarized radiant action patterns of the crossed figure of eight type and which is particularly adapted for direction finding purposes.

A still further object of the present invention is the provision of an antenna structure of the type hereinbefore described which may be directly supported on a metallic mast or other supporting structure without the use of insulators.

Other and further objects of the present invention will become apparent and the foregoing will be best understood from the following description of embodiments thereof, reference being had to the drawings in which:

Fig. 1 is a bottom plan view of a preferred form of antenna structure in accordance with the present invention;

Fig. 2 is a front elevational view in perspective of the antenna structure of Fig. 1 and includes a schematic diagram of the connections of said antenna with a signal system;

Fig. 3 is a front elevational view of a modified form of antenna structure in accordance with the present invention; and

Fig. 4 illustrates substantially the radiant action pattern of said antenna structures.

In the antenna structure of Figs. 1 and 2, the radiant acting elements consist of four loops l, 2, 3 and 4, each of the concentric line type having an inner conductor 5- and an outer conductor 6.

Each of the loops I through i is horizontally disposed in the same horizontalplane and is sub.-. stantially in the form of an isosceles triangle having equal sides 1, and 8;; 9 and Ill; H- and i2; and i3 and I4 respectively. Triangular loops 5 through 4 are symmetrically disposed around a central point and have their apices arranged adjacent each other at the center of the. array with their bases 15 through l8; forming asubstane tially closed, square geometrical pattern. for the array.

Adjacent sides of adjacent triangular loops run alongside and abut each other. 130. insure that the electrically eifective lengths ofsuch adjacent sides are equaland: to provide-a rugged structure, said adjacent sides are preferably connected along their length as, for; example, by soldering, and each pair of adjacent sides is en.- closed in. a close-fitting metallic shield 2'1]. The shields 2c are all of, the same lengthso that the array is electrical y balanced. Each of the shields 20, extend from a. central metallic junction box 2i to one of a, plurality of metallic junctionboxes 22, each of said junction boxes 22 being arranged at the outer end of a pair of adjacent sides such as, for example, sides Hi and ll. The adjacent sides are crossed over within junction boxes 22, and are horizontally coplanar outside of said boxes.

Each of the loops l through 4 is open at its inner end, that is, at: its apex, and opposite loops are connected to each other in parallel. More specifically, the inner ends. of sides 1, andilv of loop I are not connected to each other but instead, said inner ends are. connected by con-. nectors 23 and 2 Av within junction-x 21; tothe inner ends. of sides [2 and II respectively of loop 3, which is opposite loop. I. Likewise the, inner end of sides 9 and it of loop. 2- are connected by connectorsv 25 and 216 respectively to the inner ends of sides i l and [3 respectively of loop 4. Connectors 23, through 26. each consist ofa short piece or 11111; of, concentric line arranged within junction box 2|.

Each of the connectors 23 through 2.6,. has its outer conductor open. at; the. center thereofi to enable connection of said connector to a transmission line, connectors. 23,- through 26. being connected respectively to concentric transmission lines 21- throu'gh 39. Transmission lines, 2] throug 8- r symm t callyarransed' ithin a metallic shield or mast 3| extending from the bottom of central junction box 2-]. and. which also serves as. a support: for the loop. array. Lines; 2? and 28 go, to one. load or-energizi-ng source and lines 29; and Sligoto, another load orenergiz ing source. Thus lines 21 and 28 form one dual transmission line, and lines 29 and 30 form another.

Said loads or sources may consist of goniometer field coils 32 and 33 whose cooperating search coil 34 may :be in turn connected to a translating device 35 which is in turn coupled to a signal device '36. If the system illustrated consists of a direction finding system, then the signal device would be an indicator whereas if the system is used as a beacon device, then the si nal device would consist of some source of modulating signals usually of audio frequencies.

To enable the loops to function as radiant acting elements, a gap or break is provided in the outer conductor 6 of each of the loops, that is, the outer conductors'of loops I through 4 are provided with gaps 3! through 40 respectively. These gaps serve to couple the inner conductor to the outer surface of the outer conductor 6 at said gaps. While the size of the gaps may be varied, it is preferred that they be made as small as possible, but not so small that the capacity between the ends of the outer conductor across said gap will effectively short said gap at the radio frequency used.

By positioning the gaps at a point in each loop directly opposite the portion of said loop arranged within the central junction box 2|, said latter portion will be at a null point of potential on said loop and therefore will not have to be insulated from said junction box and its supporting mast 3|. Thus, for example, gap 31 is directly opposite said connector 25 of loop I and said connector is at a null potential point in relation thereto. Thus the connector 25 does not have to be insulated from the central junction box 2 I. It will be seen that in this arrangement, the gap 31 is directly opposite the apex of the triangular configuration of loop I' and is located at a midpoint of the base of this triangle. Gaps 38, 39 and 40 are similarly arranged.

I nection with the details of specific structures, it

diant action also, while still providing a crossed figure of eight radiant action pattern. This may be accomplished by providing vertical dipoles adjacent each of the gaps in the following manner.

Referring now to Fig. 3 in which the numerals applied to the elements illustrated in Figs. 1 and 2 are applied to the same elements in Fig. 3, a dipole is arranged at gap 31 with the upper member 4| of the dipole on the left side of the gap and the lower member 42 on the right side of the gap. At the opposite gap 39 the lower member43 of a dipole is arranged on the left side of the gap while the upper member 44 is arranged at the right side of the gap. It will thus be seen that the dipoles are oppositely arranged on opposite sides of the structure so that they are 180 out of phase and yield a cross-over of the electrical connections, thus providing a figure 8 radiant action pattern. In similar fashion, dipoles, are arranged adjacent gaps 38 and with the upper and lower member of the dipole at gap 38 oppositely disposed in relation to the upper and lower member at gap 40. The dipoles thus produce vertically polarized radiant action patterns of the crossed figure of eight type which patterns will coincide with those produced by the horizontally polarized loops.

While I have described my invention in conwill be obvious that modifications in these details may be made without departing from my invention. For example, the junction boxes 22 may be dispensed with. Instead of having four transmission lines'21 through 30 going down through the mast 3|, connectors 25 and 26 may be connected to-one balanced dual transmission line and connectors 23 and 24 may be connected to another balanced dual transmissionline. Other I modifications Within the scope of my invention The arrangement heretofore described in connection with Figs. 1 and 2 has a radiant action pattern sharply plane polarized and in the system described, this polarization is horizontal. The current flows in opposite loops in opposite clockwise directions, that is when the current runs clockwise around loop I it runs counterclockwise aroundloop 3, and when it runs clockwise around loop 2 it runs counterclockwise around loop 4. The radiant action pattern produced is substantially as shown in Fig. 4 and is of the crossed figure of eight type. In order 'to prevent distortion of the pattern by various in terfering influences such as, for example, the vertical components of downwardly inclined waves, it is preferred that the dimensions of the radiant action portions of the structure be as small as possible for the sensitivityor pick-up required. It is preferred, for example, that the sides of the array, morespecifically the length of the base of each of the triangular loops, be less than one-eighth of the shortest wavelength to will occur to those versed in the art, from the foregoing description.

Accordingly, while I have described above the principles of my invention in connection with specific apparatus and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth'in the objects and the claims. 1 I claim: r

1. A radio antenna structure providing 'a crossed figure of eight radiant action pattern for plane polarized waves comprising four symmetrical loops disposed in the/same plane immediately adjacent each other around a central point to form a substantially closed geometrical pattern, each of said loops being open adjacent said central point to provide a pair of open ends, the open ends of each pair of opposite loops being connected in parallel to each otherand to a dual transmission line. v J

2. A radio antenna structure according to claim 1 wherein the loops are each substantially in the form of a triangle and'are mounted with their apices adjacent "said central point, their sides contiguous and their bases forming a substantially closed square.

. 3. A radio'ante'nna structure according to claim 1 wherein each of the loops is formed of aconcentric line having an inner and outer conductor,'and the outer conductorof each loop has a gap therein to effectively couple the outside of said outer conductor to said inner conductor.

' 4'. A radio antenna structure according to claim 1 wherein each of the'loops is formed of a concentric line having .an' inner and outerbonduc- I) tor, and the outer conductor of each loop has a gap therein at a point of said loop substantially equally spaced around said loop from said central point.

5. A radio antenna structure according to claim 1 wherein each of the loops is formed of a concentric line having an inner and outer conductor, and the outer conductor of each loop has a gap therein at a point of said loop opposite said central point, and a conductive support member on which said loops are directly supported at portions of said loops adjacent said central point.

6. In combination with a radio antenna structure according to claim 1, a goniometer having two coils at right angles to each other, each of said coils connected with one of said dual transmission lines, and a search coil, a translating device connected to said search coil, and a signal device connected with said translating device.

'7. In a direction finder, the combination with a radio antenna structure according to claim 1, of a goniometer having two coils at right angles to each other, each of said coils connected with one of said dual transmission lines, and a search coil, a receiver connected to said search coil and a visual indicating device connected with said receiver.

NATHAN MARCHAND.

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