US2495747A - Antenna - Google Patents

Description

Jan. 31, 1950 F. J. LUNDBURG ANTENNA Filed Nov. 8, 1945 2 Sheets-Sheet l A TTORNFY Patented Jan. 31, 1950 ANTENNA Frank J. Lundburg, New York, N. Y., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application November 8, 1945, Serial No. 627,489

13 Claims. 1

This invention relates to antennas and more particularly to wide band antennas having a consistent, desired radiation pattern over a considerable range of frequencies.

In certain applications of the radio communications art, such as direction finding, it is frequently necessary to employ two or more antennas in fairly close proximity to one another. Under such circumstances, the mutual interaction of the radiation of one antenna with respect to an adjacent one is undesirable.

It is an object of the present invention to provide an antenna which causes a consistent radiation pattern to be established over a wide range of frequencies.

It is another object to provide an antenna which has a radiation pattern extending straight ahead of the antenna and covers substantially a 45 range on each side of the center line of the pattern.

It is a further object to provide an antenna which causes the establishment of a substantially spherical, strictly defined and forwardly-directed radiation pattern.

It is another object to provide an antenna which has a radiation pattern characteristic which permits of the use of more than one antenna in relatively close proximity to one another without mutual disturbances.

In accordance with certain features of the invention, I provide a radiator which consists of a hemispherical portion which has two opposite side portions thereof cut away in part, and which is fed by means of a pair of plates in the plane of the base of the hemisphere separated by a relatively narrow slot across which slot energy is applied from a transmission line.

These and other objects and features of the invention will become apparent and my invention will be best understood from the following description of an embodiment thereof, reference being had to the drawings, in which:

Fig. 1 is a top, plan view of the antenna in accordance with my invention;

Fig. 2 is a sectional View of the antenna taken .on line 2-2 of Fig. 1;

, used to produce the pattern of Fig. 3;

Fig. 4 is a View illustrating the use of two antennas of my invention having radiation patterns similar to those of Fig. 3; and

Fig. 5 is a perspective View of an alternative form for the antenna.

Referring now to the drawings, the antenna shown in Figs. 1 and 2 consists of a basic hemisphere I which has been partly cut away at the two opposite portions thereof as indicated at 2 and 3, the resulting openings 4 assuming a somewhat paraboloid form as might be obtained at the time of intersection between a hemisphere and a cylinder, with their major axes substantially parallel. The hemisphere, which is the radiator portion of the antenna, is fed from a transmission line 5 and t connected to two sides I and 8 of a slot 9 formed between two feed plates iii and it. These plates l0 and H are disposed in the plane of the base of the hemisphere and constitute a network which is matched to the characteristic impedance of the transmission line 5, 5. To provide a forwardly and uni-directional pattern, a reflector E2 in parallel relationship to the feeding plates l0 and l l is used.

The character of the two feed plates is preferably such that within a 3-to-1 frequency band ratio, their impedance falls within a 2-to-1 ratio. This may be approximated by making the radius r of the cut of each of the feed plates substantially equal to the width of the waist to of the radiator. In order to attain the desired consistent pattern over a wide range of frequencies, it will be required to dimension the hemisphere such as to make the longest line interconnecting two points in the base of the radiating portion I in a plane perpendicular to the plane of the base equal to a 0.59 wavelength at the mid-frequency. This will insure that a maximum current distribution will be maintained at all times over the top or forward section of the hemisphere.

In an actual antenna for use over a 2-to-1 frequency band, it was found that in a preferred form for the ultra-high frequency range, the diameter of the hemisphere should approximate of a wavelength at the mid-frequency of the band, the width of the waist w being about of a wavelength and the width We of the feed platesat their points of meeting with the radiator about of a wavelength. The spacing of the reflector l2 from the base of the radiator is preferably about of a wavelength. An antenna of this type is productive of radiation patterns for her of the antenna used in producing these patterns has been illustrated which had the diameter of four inches, the reflector being spaced two inches from the radiator base. Field patterns for siX frequencies as indicated were obtained. The antenna was positioned for vertical polarization and was made directional by using a thirtysiX inch square reflector mounted two inches behind the radiator.

The view of Fig. 4 illustrates how two antennas may be used in fairly close proximity without causing intercoupling between the antennas. Since the radiation is substantially zero transversely of the array there will be practically no coupling therebetween. This type of application is of particular importance in direction finding.

The form of antenna shown in Fig. 5 utilizes for the radiating portion I a rectangular sheet of metal bent into a semi-circle which is fed in accordance with the feeding method shown for the antenna of Fig. 1.

While a specific form Of antenna has been shown, it should be noted that alternative forms are contemplated here. Other forms of cuts may be taken in the hemisphere which may be smaller or larger than the ones indicated and may possibly have somewhat different shapes. Other forms for the feeding plates are also within the present scope. of using a complete hemisphere, as shown, a different segment of the sphere may be used.

Thus, while I have described above the principles of my invention in connection with specific apparatus, 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 defined in the accompanying claims.

I claim:

1. An antenna comprising a pair of radiant energy-feeding members disposed in one plane and spaced to form a slot between the edges of said feeding members, transmission line means arranged to feed energy to said feeding members at opposite sides of said slot, and a radiating member conductively connecting the two furthest opposite edge portions of said feeding members having a hemispherical contour and cut-away portions at opposite ends of the axis of said slot for producing radiation within a narrow sector.

2. An antenna according to claim 1 wherein said feeding members comprise two flat electroconductive members.

3. An antenna according to claim 1 wherein said feeding members comprise a matching network for said transmission line, the impedance of which remains within a two-to-one ratio for a frequency band ratio of three-to-one for the antenna.

4. An antenna according to claim 1 wherein the great circle portion of the contour of said radiating member comprises substantially 0.59 wavelength between said feeding members.

5. An antenna comprising a pair of radiant energy-feeding members disposed in one plane and spaced to form a slot between the ends of said feeding members, transmission line means arranged to feed energy to said feeding members at opposite sides of said slot, and a radiating member conductively connecting the two furthest opposite edge portions of said feeding members comprising a hemispherical portion, the base of which is in the plane of said feeding members having portions cut-away at opposite ends of a diameter through said slot.

It is also clear that, if desired, instead 6. An antenna according to claim 5 wherein said two cut-away portions are determined by the lines of intersection between said hemisphere and two cylinders.

7. An antenna according to claim 5 wherein said two cut-away portions are determined by the lines of intersection between said hemisphere and two cylinders, the axes of said hemisphere and said cylinders being substantially parallel.

8. An antenna according to claim 5 wherein said feeding members comprise two fiat conductive members having a portion of their outside edges meeting with the hemisphere, the remaining inside edge portions thereof being obtained by a out having a radius substantially equal to the narrow portion of the hemisphere between the two cut-away portions.

9. An antenna according to claim 5, wherein said feeding members comprise a matching network for said transmission line, the impedance of which remains within a. two-to-one ratio for a frequency band ratio of three-to-one for the antenna.

10. An antenna according to claim 5, further including a reflecting member spaced adjacent and parallel to said feeding members.

11. An antenna array comprising at least two antennas disposed substantially side-by-side and arranged to produce mutuall non-interfering radiation patterns in a given direction, each comprising: a pair of radiant energy-feeding members disposed in one plane and spaced to form a slot between the ends of said feeding members, transmission line means arranged to feed energy to said feeding members at opposite sides of said slot, and a radiating member conductively con meeting the two furthest opposite edge portions of said feeding members having a contour which is at least a part of a semi-circle in a plane perpendicular to that of said feeding members, whereby substantially zero radiation will be obtained transversely of the array.

12. An antenna array corrnorising at least two antennas disposed substantiall side-by-side and arranged to produce mutually non-interfering radiation patterns in a given direction, each comprising: a pair of radiant energy-feeding members disposed in one plane forming a slot therebetween, transmission line means arranged to feed energy to said feeding members at opposite sides of said slot, and a radiating member conductively connecting the two furthest opposite edge portions of said feeding members comprising a hemispherical portion, the base of which is in the plane of said feeding members having portions cut away at opposite ends of a diameter through said slot, whereby substantially zero radiation will be obtained transversely of the array.

13. An array according to claim 12, further including for each of said antennas a reflecting member spaced adjacent and parallel to said feeding members.

FRANK J. LUNDBURG.

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

UNITED STATES PATENTS Number Name Date 2,138,900 Berndt et a1 Dec. 6, 1938 2,235,506 Schelkunoff Mar. 18, 1941 2,372,228 Schelkunoff Mar. 27, 1945 2,414,266 Lindenblad Jan. 14, 1947

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