US3518692A - Orthogonal antenna system with multiple-channels - Google Patents

Description

June 30, 1970 J. A. KUECKEN ORTHOGONAL ANTENNA SYSTEM WITH MULTIPLE-CHANNELS Filed Aug. 25. 1967 Fig.

I N VEN TOR. JOHN A. KUECKE/V United States Patent Office 3,518,692 Patented June 30, 1970 3,518,692 ORTHOGONAL ANTENNA SYSTEM WITH MULTIPLE-CHANNELS John A. Kuecken, Pittsford, N.Y., assignor to General Dynamics Corporation, a corporation of Delaware Filed Aug. 25, 1967, Ser. No. 663,396 Int. Cl. HOlq 21/26 U.S. Cl. 343-797 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to receiving and transmitting antenna systems, and more particularly the invention relates to antenna systems having a plurality of independent (decoupled) radiators.

There has long been a need for antenna systems which provide, in a unitary structure, a system which simultaneously broadcasts or receives radio waves in the same frequency range, without interference. In other words, the radiators provide a high degree of mutual isolation between each other.

In view of the foregoing it is an object of the present invention to provide an improved multi-channel antenna system in which the radiators are electrically isolated from each other.

A further object of the present invention is to provide a multi-channel antenna system which may be mounted in a limited space and which is substantially maintenance free.

Briefly described, an antenna system in accordance with the invention employs three mutually orthogonal dipole radiators decoupled from each other but mounted in close proximity in a feed box. Each radiator intersects a horizontal plane with the same angle. By means of this symmetrical relationship, any radiator will tend to induce cancelling currents in the other radiators, thereby providing high mutual isolation.

Preferably, the radiators are dipoles having two separate radiating elements. Moreover, each radiator is coupled to its source by means of a hybrid device which has a feature of enhancing mutual isolation between the radiators.

The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof will become more readily apparent from a reading of the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a diagrammatic, perspective illustration of an antenna system in accordance with the present invention;

FIG. 2 is a detailed view of one of the radiators shown in FIG. 1; and

FIG. 3 is a schematic illustration of the hybrid feed device shown in FIG. 2.

Turning first to FIG. 1, an antenna system is shown comprising three mutually orthogonal dipole radiators 11, 12 and 13 which are electrically decoupled from each other but mounted in the same di-electric feed box 15. The box 15 holds each radiator so that its axis intersects a horizontal plane with the same or equal angle. The

feed box 15 is supported by a di-electric mast 18 about which a choke structure 19 is employed to isolate and break up RF currents on a plurality of coaxial feed cables 20 (one coaxial cable for each radiator).

By means of this arrangement each radiator provides an omni-directional coverage and, because of the symmetry of it in relation to the other radiator, tends to induce cancelling currents in them, thereby providing high mutual isolation between radiators.

As shown in the drawings, each radiator is effectively comprised of two individual radiating elements, for example, radiator 11 has elements 11a and 11b. The following discussion is given with respect to the radiator 11 but is equally applicable to the radiators 12 and 13. Preferably, the elements 11a and 11b should be fed in phase opposition to provide an additive radiation field during broadcasting. To accomplish the function, a hybrid feed device shown in FIG. 2 and in detail in FIG. 3 is provided. Turning briefly to FIG. 2, the hybrid 30 permits the center of the feed box to be vacant so that the other radiators may be inserted diagonally through holes (one of which is chosen by dotted lines and given number 32) in the box 15 to facilitate radiator stacking or emplacement.

Turning now to FIG. 3, the hybrid device 30 includes two bi-filar wind coils 36 and 37 which may consist of a coaxial cable wound about a torroidal shaped metallic member. The coil 36 has a first winding 36a and a second winding 36b; similarly the coil 37 has a first winding 37a and a second winding 37b. The radiator 11a is serially connected to the winding 36a and the winding 37b which in turn is coupled at a junction 40 to a grounded resistive load 42. In a like manner, the element 11b is connected in series to the winding 37a and the winding 36b, the latter of which is also connected at the junction 40. The outer conductor 20a of the coaxial cable 20 is connected at the electrical junction 48 of the windings 26a and 37b, whereas the inner conductor 20b is connected at the electrical junction 50 of the windings 26b and 37a.

Accordingly, the cable 20 has two separate path connections to the junction 40, one traced through the inner conductor 20b and the other through the outer conductor 20a. Moreover, the coaxial cable 20 is connected to the element 11a through its outer conductor 20a. By means of this arrangement, an impressed signal will excite the radiating elements 11a and 11b in phase opposition and if the loads presented by the elements 11a and 11b to the signal source are identical, no output will be produced at the junction 40. Should a slight unbalance occur, by for example the element 12a exciting more current in the elements 11a and 11b than the cancelling current excited from the element 12b, an induced current would appear as a result of the in-phase excitation of the elements 11a and 11b. The hybrid circuit directly couples this induced current into the resistive load 42.

Thus, with a signal impressed upon the cable 20, the cable 20 is electrically coupled to the elements 11a and 11b but isolated from the resistor 42; whereas any inequality of signals induced in the elements 11a and 11b from another radiator will be electrically coupled to the resistor 42 from the elements but the cable 20 will be partially isolated therefrom. The hybrid 30 greatly increases the isolation between the various elements and permits the attainment of effectively independent operation between the radiators when they are in operation.

The radiation pattern of the antenna being essentially that of a dipole is very nearly a cosine formation of the E plane. However, it has been determined that the E plane of each radiator is inclined at an angle to the vertical; and the maximum radiation of the E plane is above and below the horizon in the plane of the antenna inclination. Although one would expect a variation in rated field strength around the horizon, quite unexpectedly in accordance with the invention, it has been found that the rotation of the pattern tends to be compensated by an equivalent rotation in the polarization pattern thereby restoring the omnidirectional character to the antenna pattern in the horizon plane.

While a single embodiment of the invention has been described, variations thereof and modifications therein within the spirit of the invention will undoubtedly suggest themselves to those skilled in the art. For example, although the illustrated hybrid device is preferred, other forms of series-parallel hybrids may also be employed in accordance with the invention. Accordingly, the foregoing description should be taken as illustrative and not in any limiting sense.

What is claimed is:

1. An antenna system comprising a plurality of electrically decoupled dipole radiators disposed adjacent to each other in mutual orthogonal relationship with each radiator intersecting a horizontal plane at an equal angle and having two radiating elements, means for feeding each of said plurality of dipole radiators, and separate means interconnecting the radiating elements of each radiator for dissipating energy induced therein from its adjacent radiators.

2. The invention as set forth in claim 1 wherein each radiator is a center-fed dipole.

3. The invention as set forth in claim 2 wherein there are three of said radiators, and said feeding means applies a different signal to each of said radiators.

4. The invention as set forth in claim 2 wherein said feeding means and interconnecting means are provided by a plurality of hybrid devices, one for each of said radiators coupled to each element of radiator in phase opposition and dissipates signals induced from the other radiators.

5. The invention as set forth in claim 4 wherein each of said hybrid devices includes a pair of hybrid transformers each coupled to a different radiating element of the radiator for which it is provided, for feeding said elements .in phase opposition, a feed line coupled to input ports of said transformers, and a dissipative load connected to said transformers for dissipating said induced energy.

6. The invention as set forth in claim 5 wherein each hybrid device comprises a first and second bi-filar wound coil, each coil having first and second windings, with the first winding of the first and second coils being respectively connected to the first and second radiating elements, the second winding of each coil being connected to said dissipative load and the first winding of the other coil, and a two wire input line, the wires of which are separately connected to the first and second windings of dilferent ones of said coils.

References Cited UNITED STATES PATENTS 3,388,400 6/1968 Veldhuis 343797 3,396,398 8/1968 Dunlavy 343844 3,354,459 11/1967 Schwartz et a1. 343854 FOREIGN PATENTS 71,507 1/ 1953 Netherlands.

OTHER REFERENCES RCA Technical Notes; RCA TN No. 226, Jan. 5, 1959; 343-797.

ELI LIEBERMAN, Primary Examiner US. Cl. X.R. 343-816, 844

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