US2413745A - Antenna - Google Patents

Description

P. SQCARTER 2,413,745 I ANTENNA Filed June 17, 1942 INVENTOR Pam/p 5. CARTER.

. ATTORNEY I v Patented Jan. 7, 1947 ANTENNA Philip S. Carter, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application June 17, 1942, Serial No. 447,312

14 Claims.

The present invention relates to antennas and, particularly, to ultra high frequency antennas operative over a very wide frequency band such as, for example, is required in the case of television transmission.

An object of the present invention is to provide an ultra high frequency antenna having an impedance which varies very little with change of frequency.

Another object of the present invention is to produce an antenna which is mechanically strong and which is inherently protected against lightning and weather damage.

The present invention consists essentially of a radiator element so arranged as to present an impedance curve against frequency with the same characteristics as a parallel tuned circuit.

It is well known that when a line which is a number of wavelengths long is teminated in a resistanc'e which does not match the line and this is excited by a source of high frequency energy, standing waves are set up on the line. At recurring points along the line an impedance is presented which is purely resistive. These points tend to move away from the terminating resistance when the frequency is lowered and tend to move toward that end when the frequency is raised. Thus, if the source of power is connected at a point where the line presents a pure resistance at one frequency and the frequency is changed a pure resistance will no longer be presented. It has been discovered that when the res stance is replaced by a series tuned circuit, such as a center fed dipole antenna, a change in its impedance with frequency either side of resonance causes the resistive points along the line to shift in position more rapidly with a change in frequency than in the case of a resistive termination. On the other hand, it has been discovered that if the resistance termination is replaced by a circuit which has the characteristics of a parallel tuned circuit, its change in impedance with frequency causes the points of pure resistance along the line to move in the, opposite direction from that in which they move when a pure resistance termination is used. These two effects may be caused to oppose each other and thus cancel. Thus, when the transmission line is of such length as to present a pure resistance to the source of power at the center of the band, the impedance will change much more slowly with frequency in the case of a parallel tuned circuit than in the case of a series tuned circuit.

Accordingly, therefore, the present invention comprises an antenna system in which the antenna has an effect on the transmission line connected thereto similar to the effect of a parallel tuned circuit, thus resulting in a much wider band of frequencies over which the system gives a uniform response.

The present invention Will be more fully understood by reference to the following detailed description, which is accompanied by a drawing in which Figure 1 is a plan view, partly in section, illustrating an embodiment of the present invention, while Figure 2 illustrates a modification thereof, Figure 2A illustrates in perspective an antenna array utilizing the structure of Figure 2, and Fig. 3 illustrates a further modification of Figure 2. v

The antenna shown in Figure 1 consists of a plurality of radiating elements It), 20, 30 lying in a horizontal plane each defining one side of a triangle. Each radiating element is discontinuous at the middle of each side of the triangle thus forming a pair of members. In the case of radiating member If), the members are identified by reference numerals l I, I2; in the case of radiating member 26, by 2! and 22 and in the case of radiating member 30, by 3| and 32. Transmission lines TL1, TLz, TLs are run from a convenient central point to adjacent ends of conductors ll, I2, 2|, 22 and 3| and 32, respectively. The transmission lines are so connected to a common transmission line TL that when line TL is connected to a transducer means, such as a source of high frequency energy, the current flows, for example, clock-wise in all of the conductors at a particular instant and counter-clockwise during the alternate half cycles. This gives the effect of parallel resonance as required above. It also results in a radiation pattern which is substantially circular in the plane of the radiating conductors. For any given, size of triangle a radiation resistance results which is relatively high, since the highest current points are at the angles of the triangle. In order to obtain a still wider frequency response than is obtainable from the parallel resonance effect mentioned above, each of the conductors ll, 12, 2|, 22 and 3|, 32 is generally conical in formation with the apices of the cones adjacent. A complete discussion of the reasons for the conical formation of the radiating conductors and of the factors influencing the relationship between the maximum diameters of the cones and their length will be found by reference to my prior Patent #2175254, granted October 10, 1939.

It should be noted that since the highest current points are at the angles of the triangle formed by the radiators Ill, 20, 30 the potentials at these points are at aminimum. Therefore, conductive metal supports S connected to the radiators at these points may be used for supporting the antenna in the desired location, either as a single unit or one element of a stacked array. These supports are indicated in transverse crosssection as though the viewing plane for the figure passed immediately above one unit of a stacked array.

The modification of the invention shown in Fi ure 2 employs half wave phase reversing loops I4, 24 in radiating members Ill and 20, respectively. The conductrs of transmission line TL are then connected to the adjacent apices of cones 3i and 32 of radiating member 30, thus enormously simplifying the energizing system for the antenna. The operation, of course, is the same as discussed for Figure 1.

The antenna array of Figure 2A utilizes a plurality of antennas as shown in Figure 2. The antennas are stacked vertically one above the other along a common vertical axis. The antennas are supported in position by conductive metal supports S, located at each corner of the polygon formed by the antennas. The antenna members are conductively connected to the supports S. All of the antennas are fed in parallel from a sinle transmission line TL with the connections to the transmission line so arranged that the antennas radiate in an inphase relationship. One antenna of the array shown in Figure 2A has the same reference numerals applied thereto as the antenna of Figure 2, while the others carry the same reference numerals primed and double primed respectively, whereby the similarity between the different antennas of the array may be more readily perceived. It is not believed that any further description of this modification of the present invention is necessary.

It will be noted that the structures shown in Figures 1 and 2 may be braced for mechanical strength. to any desired extent along the planes indicated by lines CL in Figure 2. These planes bisect the angles of the triangle and are, therefore, neutral puanes. If an array of two or more triangular radiating elements are located in planes parallel to each other and with a common axis, the resultant structure may be made quite rigid by means of cross-bracing in the bisecting planes.

The modification shown in Figure 3 results in a somewhat improved uniformity of the radiated field. The conductors H, l2, 2|, 22 and 3| and 32 are arranged along the sides of a heXagon in this modification. The antenna of Figure 3 is energized in the same way as described with reference to Figure 2 and may also be cross-braced in the same way as described with reference to Figure 2.

While I have particularly shown and described several modifications of my invention, it is to be distinctly understood that my invention is not limited thereto but that improvements within the scope of the invention may be made.

I claim:

1. A short wave broadcast antenna includin a plurality of radiating elements arranged along the sides of a polygon and conductively connected at each angle of said polygon. each of said elements including a pair of conical members having their apices adjacent. and means coupled to said apices for so energizing said elements that at any instant current travels all around said polygon in one direction.

2. A short wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of coaxial conical members having their apices adjacent, the adjacent bases of said conical members bein connected together, and means coupled to said apices for so energizing said elements that at any instant current travels all around said polygon in one direction.

3. A short wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of conical members having their apices adjacent, the adjacent bases of said conical members being connected together, and means coupled to said apices for energizing said elements for unidirectional instantaneous current flow around said polygon.

4. A short wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of conical members having their apices adjacent, the adjacent bases of said conical members being connected together, means for coupling transducer means to one pair of adjacent apices and phase reversing loops connected between each other pair of adjacent apices.

5. A short Wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of conical members having their apices adjacent, the adjacent bases of said conical members being connected together, and means coupled to said apices for energizing said elements for unidirectional instantaneous current flow around said polygon, and means at each corner of said polygon for supporting said antenna.

6. A short wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of conical members having their apices adjacent, the adjacent bases of said conical members being connected together, means for coupling transducer means to one pair of adjacent apices and phase reversing loops connected between each other pair of adjacent apices, and means at each corner of said polygon for supporting said antenna.

'7. A short Wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each ofsaid elements including a pair of conical members having their apices adjacent, the adjacent bases of said conical members being connected together, and means coupled to said apices for energizing said elements for unidirectional instantaneous current flow around said polygon, and conductive supporting parts connected to said members at corners .of said polygon.

. 8. A short Wave broadcast antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of conical members having their apices adjacent, the ad: jacent bases of said conical members being con- .nected together, means for coupling transducer means to one pair of adjacent apices and phase reversing loops connected between each other pair of adjacent apices, and conductive supporting parts connected to said members at corners of said polygon.

9. A short wave broadcast antenna array including a plurality of antennas as set forth in claim 1, coaxially arranged in parallel planes.

10. A short wave broadcast antenna array including a plurality of antennas as set forth in claim 3, coaxially arranged in parallel horizontal planes.

11. A short wave broadcast antenna array including a plurality of antennas as set forth in claim 5, coaxially arranged in parallel horizontal planes.

12. A short Wave broadcast antenna array including a plurality of antennas as set forth in claim 8, coaxially arranged in parallel horizontal planes.

13. An antenna for a short Wave broadcast antenna array, said antenna being adapted to be coaxially arranged in parallel planes with a plurality of other similar antennas, said antenna including a plurality of radiating elements arranged along the sides of a polygon, each of said elements including a pair of coaxial conical members having their apices adjacent, the adjacent apices of said conical members being connected together and means coupled to said apices for so energizing said elements that at any instant current travels all around said polygon in one direction.

14. An antenna for a short wave broadcast antenna array, said antenna being adapted to be ccaxially arranged in parallel horizontal planes with a plurality of other similar antennas, said antenna including a plurality of radiating elements arranged along the sides of a polygon lying in a horizontal plane, each of said elements including a pair of coaxial conical members having their apices adjacent, the adjacent apices of said conical members being connected together and means coupled to said apices for so energizing said elements that at any instant current travels all around said polygon in one direction and conductive vsulrlporting means connected to said members at the corners of said polygon.

PHILIP S. CARTER.

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