Title:
DISCONE ANTENNA
United States Patent 3641578


Abstract:
A multimode discone antenna providing simultaneously, without interference, right- and left-hand circularly polarized omnidirectional patterns and a vertically polarized omnidirectional pattern. Four coaxial cables are disposed parallel to each other with the outer conductors electrically coupled together. An extension of the central conductor of each coaxial line is extended downward from the upper end of and at a given angle less than 90° to the associated one of the coaxial lines. This arrangement, when the two pairs of diagonally disposed coaxial lines are excited in a balanced relationship and the pairs are excited orthogonally by first energy, provides simultaneously both right- and left-hand circularly polarized omnidirectional patterns. When a disc is electrically connected to the outer conductors of the four coaxial lines and is physically supported in spaced and orthogonal relation to the upper end of the four coaxial lines, the antenna, in addition, simultaneously provides, when each of the four coaxial lines are excited in phase by second energy, a vertically polarized omnidirectional pattern. An embodiment of a feed arrangement is disclosed enabling the four coaxial lines to be excited in phase by the second energy and simultaneously to enable each of the four coaxial lines to be excited by the different orthogonally related first energy.



Inventors:
Spanos, William M. (Wayne, NJ)
Polgar, Michael S. (Ocean Port, NJ)
Application Number:
05/056830
Publication Date:
02/08/1972
Filing Date:
07/21/1970
Assignee:
INTERNATIONAL TELEPHONE AND TELEGRAPH CORP.
Primary Class:
Other Classes:
333/117, 342/365, 342/373, 343/846
International Classes:
H01Q21/26; (IPC1-7): H01Q1/48; H01Q13/00; H01Q21/00
Field of Search:
343/796-802,806,846,808,809,850-865,773 333
View Patent Images:
US Patent References:
2511899Antenna system1950-06-20Brown



Primary Examiner:
Lieberman, Eli
Assistant Examiner:
Nussbaum, Marvin
Claims:
We claim

1. A multimode vertically polarized omnidirectional pattern, a right-hand circularly polarized omnidirectional pattern and a left-hand circularly polarized omnidirectional pattern comprising:

2. An antenna according to claim 1, wherein:

3. An antenna according to claim 1, wherein:

4. An antenna according to claim 1, further including;

5. A multimode discone antenna capable of having simultaneously a vertically polarized omnidirectional pattern, a right-hand circularly polarized omnidirectional pattern and a left-hand circularly polarized omnidirectional pattern comprising:

6. An antenna according to claim 5, wherein:

7. An antenna according to claim 5, wherein;

8. An antenna according to claim 5, further including:

Description:
BACKGROUND OF THE INVENTION

This invention relates to antennas and more particularly to discone antennas.

Because of existing space limitations and a need for greater numbers of antennas to provide radiating means for a multiplicity of services, the trend in antenna design is toward compact multipurpose radiators which provide more than one function. For example, in mobile applications, requirements exist for providing radio communications and navigation functions simultaneously in either different frequency bands, or in the same frequency band. The antenna radiation characteristics with respect to pattern coverage and polarization are not necessarily identical. The advent of communications and navigation systems which utilize satellites have greatly complicated the design of common multipurpose antennas because of requirements for pattern coverage and polarization which differs from those for line-of-sight (LOS) ground-to-ground and ground-to-air links. The satellite systems require circular polarization and overhead coverage from ground base antennas, necessitating different modes of excitation in the antenna from those used for conventional systems.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a multimode antenna suitable for utilization in satellite systems.

Another object of the present invention is to provide a multimode discone antenna capable of having simultaneously a vertically polarized omnidirectional pattern, a right-hand circularly polarized omnidirectional pattern and a left-hand circularly polarized omnidirectional pattern.

Still another object of the present invention is to provide a multimode discone antenna capable of utilization with satellite systems, LOS communication systems and/or navigation systems.

A feature of the present invention is the provision of a multimode discone antenna capable of having simultaneously a vertically polarized omnidirectional pattern, a right-hand circularly polarized omnidirectional pattern and a left-hand circularly polarized omnidirectional pattern comprising four coaxial transmission lines disposed in a parallel relationship, each of the coaxial lines including an inner conductor and an outer conductor; first means to electrically and physically interconnect the outer conductors of all the coaxial lines; and four first members each coupled to the center conductor of a different one of a coaxial line and extending downwardly from an end of, and at a given angle less than 90° to, the associated one of the coaxial lines.

Another feature of the present invention is the provision of four second members each coupled to the free end of a different one of the above-mentioned first members and extending downwardly and toward the associated one of the coaxial lines at an angle less than 180° and greater than 90° .

A further feature of the present invention is the provision of a disc and a second means to electrically connect the disc to the above-mentioned first means and to physically support the disc spaced from the end of, and orthogonal to, the above-mentioned coaxial lines.

Still a further feature of this invention is the provision of a multimode discone antenna as described above wherein each of the four coaxial lines are excited by in-phase energy and simultaneously each of the coaxial lines are excited by different orthogonally related energy.

BRIEF DESCRIPTION OF THE DRAWING

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a multimode discone antenna and its feed arrangement in accordance with the principles of the present invention;

FIG. 2 is a top view of FIG. 1;

FIG. 3 is a schematic illustration of the electric field and current configuration for in-phase excitation of the coaxial lines of FIGS. 1 and 2;

FIG. 4 is the elevational pattern resulting from the electric field and current configuration as illustrated in FIG. 3;

FIG. 5 is a schematic illustration of the electric field and current configuration when the four coaxial lines of FIGS. 1 and 2 are subjected to a balanced excitation; and

FIG. 6 illustrates the elevational pattern resulting from the electric field and current configuration illustrated in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For purposes of explanation, let us consider a UHF (ultrahigh frequency) line-of-sight (LOS) ground-to-ground communication, UHF satellite communications and L-band DME (distance-measuring equipment)/Tacan or RSB (Radar Safety Beacon)/IFF (Identification Friend or Foe) applications wherein the following requirements would exist for an antenna at a user terminal.

Function Polarization Frequency Pattern Coverage Band __________________________________________________________________________ UHF LOS Vertical 225-400 MHz. Figure 8 in Communications elevation, omnidirectional UHF Dual Circular 225-400 MHz. hemispherical Satellite Communication DME/ Vertical 960-1,215 MHz. Figure 8 in Tacan, elevation, RSB/IFF omnidirectional __________________________________________________________________________

The term "dual circular" as presented in the above table refers to right and left hand circularly polarized radiation. The term "hemispherical" present in the above table has reference to a right- and left-hand circularly polarized omnidirectional pattern.

Referring to FIGS. 1 and 2, there is illustrated therein a multimode discone antenna in accordance with the principles of the present invention including four coaxial transmission lines 1-4, each of which includes an outer conductor 5 and an inner conductor 6. The outer conductors 5 of coaxial lines 1-4 are interconnected electrically and physically by members 7 and 8. To the center conductors 6 at the upper end thereof is connected a member 9 extending downward from the upper end of coaxial lines 1-4 and at a given angle less than 90° to the associated one of coaxial lines 1-4.

The structure just described provides a hemispherical antenna pattern when each of the pairs of coaxial lines 1 and 4 and coaxial lines 2 and 3 are excited in a balanced relationship and these pairs of coaxial lines are orthogonally excited by a given energy for transmission from the antenna structure, or when hemispherically radiated energy is received by radiating elements 9. The radiating elements 9 in the form of wire or rods is equivalent to the cone of a discone antenna and due to its hemispherical antenna pattern provides the multifunction of providing both right- and left-hand circular polarization with an omnidirectional pattern. This arrangement as just described would be suitable for UHF satellite communication as indicated in the above table.

To aid in the producing of the desired shape of the antenna pattern and also to adjust the impedance of the antenna structure, second members 10 are coupled to the free end of each of the members 9 and arranged to extend downwardly and toward the associated one of coaxial lines 1-4 at an angle between members 9 and 10 less than 180° and greater than 90°. The angle between each of the members 9 and 10 enables variation for space consideration and also impedance considerations in the antenna structure as well as the shape of the antenna pattern.

To provide vertical polarization for UHF LOS communications or DME/Tacan, RSB/IFF applications, a disc 11 is disposed orthogonal to the parallel coaxial lines 1-4. Disc 11 is electrically connected to the outer conductors 5 of coaxial lines 1-4 by physical connection to members 7 and 8 via feed member 12 which is physically coupled to the center of disc 11. Feeder 12 also provides an electrical connection between the outer conductors 5 of coaxial lines 1-4 and disc 11. Current flows on outer conductor 5 of coaxial lines 1-4 due to inphase excitation thereof which could cause the coaxial lines to radiate and disturb the desired patterns. In accordance with this invention, a high impedance to this current flow and, hence, elimination of the unwanted radiation is provided by the one-quarter wavelength choke 19 having the end 20 thereof in electrical contact with outer conductor 5 of coaxial lines 1-4.

Disc 11 has a diameter approximately equal to 0.7 D, where the dimension D is illustrated in FIG. 2, at the operating frequency while wires 9 and 10 each have a length greater than a quarter wavelength. The lengths of wires 9 and 10, as well as the distance D, controls the radiation patterns generated by the antenna of this invention.

Another important dimension is the space between the ends of coaxial lines 1-4 and disc 11 as provided by the length of member 12 and also the diameter of member 12. The spacing, as provided by the length of member 12, and the diameter of member 12 may be adjusted to control the impedance levels of the antenna structure of this invention.

To provide transmission of vertically polarized omnidirectional energy, coaxial lines 1-4 must each be energized by the desired energy in-phase and upon reception of vertically polarized omnidirectional energy coaxial transmission lines again will be excited in-phase by the received energy.

FIG. 3 illustrates by virtue of the solid arrows the electrical field configuration when the antenna structure and, particularly, the coaxial lines 1-4 are excited in-phase. The dotted arrows illustrated the current flow present in the diagonally related members 9 and 10.

FIG. 4 illustrates the elevational antenna pattern resulting from the electric field and current configuration as illustrated in FIG. 3.

FIG. 5 illustrates by the solid arrows the electric field configuration when the antenna structure and, particularly, coaxial lines 1 and 4 and coaxial lines 2 and 3 are excited in a balanced relationship and these pairs are orthogonally excited through means of quadrature hybrid 15 by the desired energy. The dotted arrows illustrate the current flow present in diagonally related members 9 and 10 of FIG. 1.

FIG. 6 illustrates the elevational antenna pattern for the circularly polarized portion of the antenna structure shown in FIGS. 1 and 2.

The feed arrangement for the antenna structure of this invention as shown in FIG. 1 used for both transmission and reception includes two balanced hybrids 13 and 14 and a quadrature hybrid 15.

For transmission the feed arrangement operates as follows. The energy to be transmitted with vertical polarization is applied to port 16 and fed in common to the in-phase port of balanced hybrids 13 and 14. This results in an in-phase excitation of coaxial lines 1-4 as indicated by the (+) symbol applied to the ports of hybrids 13 and 14 connected to the center conductors of coaxial lines 1-4. This inphase excitation of the coaxial lines 1-4 will result in the figure-eight elevational antenna pattern provided by members 9 and 10 and disc 11.

The circular polarization pattern for transmission is simultaneously provided by exciting port 17 of quadrature hybrid 15 with left-hand circularly polarized signal and port 18 of quadrature hybrid 15 with right-hand circularly polarized signal. This results in a 0° phase shift for left-hand circularly polarized signal (a 90° phase shift for right-hand circularly polarized signal) at port 21 of hybrid 15 which is coupled to the balanced port of hybrid 13 and produces a 0° phase shift for left-hand circularly polarized signal (a +90° phase shift for right-hand circularly polarized signal) for excitation of transmission line 4 and a 180° phase shift for left-hand circularly polarized signal (a -90° phase shift for right-hand circularly polarized signal) for excitation of transmission line 1. Simultaneously, the energy applied to ports 17 and 18 is coupled from port 22 of hybrid 15 to the balanced port of hybrid 14 resulting in a +90° phase shift for left-hand circularly polarized signal (a 0° phase shift for right-hand circularly polarized signal) for excitation of transmission line 3 and a -90° phase shift for left-hand circularly polarized signal (a 180° phase shift for right-hand circularly polarized signal) for excitation of transmission line 2. The resultant excitation of coaxial lines 1-4 with different balanced and orthogonal energy results in a circularly polarized signal radiated from the antenna structure including members 9 and 10.

When the antenna structure of FIG. 1 is employed for receiving left- and right-hand circularly polarized energy members 9 and 10 cause coaxial transmission lines 1-4 to be excited balanced and in-phase quadrature and excite the ports of hybrids 13 and 14 identified as the 0° (+90), 180° (-90°), +90° (0°) and -90° (180°) ports. There then will result at the output of ports 17 and 18, an output signal transmitted by the circularly polarized signal. When the antenna structure including members 9 and 10 and disc 11 receive vertically polarized omnidirectional radiation, coaxial transmission lines 1-4 are excited by in-phase received signals as indicated by the (+) ports of hybrids 13 and 14. The output from the in-phase ports of hybrids 13 and 14 are coupled to port 16.

While we have described above the principles of our invention in connection with specific apparatus, it is to be more clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.