US2101674A - Antenna - Google Patents

Description

Dec.7, 1937. R BDQME f 2,101,674

ANTENNA Filed Ma 25, 1934 HELD INTENSITY E E 54st CURRENT l E TOP CURRENT I5 50 I00 2H0 500 400 Irfiventor: Robert B. Dome,

.is Attorngy' Patented Dec. 7, 1937 UNITED STATES PATENT oFFlcE General Electric New York Company, a corporation of Application May 25, 1934, Serial No. 727,437

13 Claims.

My invention relates to antennae and more particularly to antennae having a vertical length less than .64 of a wavelength of the wave at which the'antenna operates. Still more particularly my invention relates to that type of antenna which is disclosed in application, Serial No. 727,409, entitled Antenna, and filed simultaneously herewith by Clifford A. Nickle. I

In the above referred to application of Nickle an antenna is disclosed and claimed having a vertical section grounded at the bottom and having a capacity area connected to the top through an inductance coil. This inductance coil may be adjusted for different values to produce diiierent current distributions in the antenna. For example, if the inductance be given a valve such that the impedance Z2 between the top of the antenna and the earth has a value where Z0 is the surge impedance of the antenna, and 9 is the length of the antenna expressed in degrees, then equal currents flow at the top and bottom of the antenna, these currents being either of like or unlike polarities dependent respectively upon whether the impedance is capacitive or inductive. Similarly if the inductance be adjusted to give the impedance Z2 the value 7' Z0 cot 6 then minimum current occurs at the base of the an tenna. For quarter wave antennae the first two distributions obtain when the reactive impedance Z2 is equal to the surge impedance of the antenna and the latter distribution obtains when it is zero, or the top of the antenna is short-circuited to earth. In the Nickle antenna the inductance serves to neutralize the reactance of the capacity existing between the capacity and earth permitting the desired results to be obtained by the use of a relatively small capacity area. 7

. One of the objects of my present invention is to provide means whereby substantially the. same results as are obtained by the Nickle antenna may be secured and in which all desired adjustments may be effected from the ground.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in' connection with the accompanying drawing in which Figs, 1 to 6 represent different terminated at its opposite end. By variation of the length of the transmission line, or by variation of the impedance at the opposite end of the transmission line, or both, the impedance looking into the open end may be varied over an extremely wide range. In accordance with my invention such a transmission line is employed, its open end being connected between the capac itance area and the antenna. Since the potential distribution along one conductor of the transmission line is approximately the same as that of the antenna itself, a single conductor may be employed for the two purposes. In this way the closed end of the transmission line is brought near to the earth 'whereby'it may be adjusted to adjust the value of the inductance at its open end as desired. The portion of the antenna active with respect to waves in space then comprises two vertical conductors. By the term active with respect to waves in space I refer to the capability of the conductors themselves to produce desiredradiation in space or to respond directly to such waves in space as impinge thereon.

Thus in Fig. 1 I have shown an antenna comprising two vertically extending conductors I and 2. While the antenna may be used either for transmission or reception, I have shown a source of exciting electromotive force 3 connected between the base of the conductor 2 and the ground. At the top of the conductor l is arranged a capacityarea 4. The conductors l and 2 comprise a transmission line which is open at the top and closed at the lower end through a jumper 5, which is variable upwardly and downwardly along the length of the antenna. In this way the length of the transmission line may be adjusted to produce any desired value of inductance between the capacity area 4 and the top of the conductor 2. In this way the desired effective inductance at the top of the antenna is produced and at the same time its value is adjustable from the ground; Thus any desired current distribution along the length of the an-.

tenna may be secured by variation of the position of the jumper 5.

Figs. 2 and 3 illustrate antennae differing from Fig. 1 only in that the impedance of the open end of the transmission line is varied by variation of an impedance 1 with which the transmission line is closed at its lower end rather than by variation of the length of the transmission line. In Fig. 2 this impedance 1 is represented as capacitive, whereas in Fig. 3 it is represented as inductive.

I have found through experimentation with antennae of these types that it is immaterial at what point upon the impedance 1 the excitation voltage produced by the source 3 be applied, and further that it is immaterial to which of the conductors I and 2 the capacity area 4 be connected, and this latter irrespective" of the position of the connection of source 3 to impedance I.

It has also'been found in the use of these antennae that the current flowing in the jumper 5 or in the impedance 1 is very large. To avoid this it is desired that the total inductance necessary at the top of the antenna to produce the desired current distribution be divided into a fixed portion and a variable portion, the fixed portion being placed at the top of the antenna as indicated at 8 in Figs. 4 and 5, and the variable portion being provided by the transmission line in the manner already described.

Figs. 4 and 5 show such an embodiment of my invention, these figures differing from each other only'that in Fig. 4 the transmission line is terminated in an impedance 1 and in Fig. 5 it is terminated in the jumper 5 which is variable in position along the length of the antenna.

In Fig. 6 I have shown a modification of my invention in which even greater inductance may be obtained at the top of the antenna and which is likewise variable from the ground. This may be effected by connecting a condenser 9 between the conductor I and the conductor 2 at the top whereby this condenser is connected in shunt with the effective inductance between these two conductors at this position. This condenser may have such a capacitance relative to the inductance between the two conductors at this point as to greatly increase the effective inductance between the two points. in accordance with the well known operation of shunt tuned circuits adjusted somewhat off resonance. desired, this condenser 9 may be enclosed-within the sphere 4 whereby it is protected from the weather.

In Fig. 7 I have shown certain characteristics plotted from experimentally obtained data on coordinates with logarithmic abscissa. This data was obtained by use of an antenna of the type shown in Fig. 1 excited with oscillations of a frequency of 7150 kilocycles. a height of 408 inches and the height of the jumper is indicated as abscissa on the graph of Fig. 7. The curve A shows the current flowing into the capacity area at the top of the antenna; It will be observed that as the jumper was raised from its lowest point this current decreased in intensity at a progressively decreasing rate and that it became substantially constant after the jumper was at an altitude of approximately 100 inches. The base current at first rapidly decreased to a somewhat critical minimum and then increased less rapidly until it became sub stantially constant when the jumper was above approximatelylOO inches. The field intensityin- The antenna had dicated by the curve C rose rapidly to a maximum point and then gradually diminished, the maximum occurring just above the point of minimum base current. The field intensity at this point, however, was not critical and remained approximately constant from the point where the minimum base current occurred to the point where the base current and top current were equal. If the antenna be used for reception the adjustment should be the same as for transmission.

While I have shown particular embodiments of my invention it will be understood that I do not wish to be limited thereto since other modifications and embodiments of the invention will occur to a person skilled in the art. I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination of an antenna of the type having a capacity area at the top and an inductance connected between said capacity area and the top of said antenna, and means whereby said inductance is produced by the open end of a transmission line closed at the end remote from said area.

2. In combination, an antenna having a ver tical section connected to ground at the bottom and having a capacitance area at the top, a second vertical conductor parallel with said first section and insulated therefrom, and means to vary the current in said connection to ground through a minimum value, said means comprising an adjustable electrical connection between said conductors.

3. The combination, in an antenna, of a conductor having a connection to ground at one end and a non-radiating non-energy absorbing capacitance area at the other, and means to vary the effectiveness of said antenna with respect to the space wave upon which it operates, said means comprising a second conductor extending along said first conductor and adjustably connected thereto, said conductors comprising the principal portion of said antenna active with respect to waves in space.

4. An antenna comprising a pair of vertically extending conductors connected together at the bottom and a non-radiating non-energy absorbing capacity area connected to the top of one only of said conductors, said conductors comprising the principal portion of said antenna active with respect to radio waves in space about said antenna.

5. In combination, an antenna having a vertical section connected to ground at one end and having a capacitance area at the top, a second conductor extending along the length of said first conductor and a connection between said conductors at a point to produce a maximum of current in a portion of the antenna nearer the capacity area than ground, said conductors being arranged to constitute the principal portion of said antenna active with respect to waves in space.

6. In combination, an antenna having a vertical section connected to ground at one end and having a capacitance area at the top, a second conductor extending along the length of said first conductor and connected to said first conductor near the ground connection through an impedance having such a value as to produce maximum current in the antenna at a point nearer the capacity area than ground the principal transfer of energy between space and said antenna occurring directly between space and said two conductors.

'7. In combination, an antenna comprising a vertical conductor having a conductive area at the top utilized solely to increase the capacitance between the top of said antenna and the earth, and a connection to earth at the bottom, and means effective to alter the effect of said antenna with respect to space radio waves, said means comprising a second vertical conductor in proximity of said first vertical conductor and connected thereto, the upper portion of said conductor being insulated from said antenna and forming therewith a transmission line having an impedance at the top dependent in value upon the connection between said conductors and proportioned relative to the dimensions of said capacity area to produce in cooperation therewith the desired alteration in the effect of said antenna with respect to space radio waves.

8. In combination, an antenna comprising a vertical conductor having a conductive area at the top utilized solely to increase the capacitance between the top of said antenna and the earth, and a connection to earth at the bottom, and means effective to alter the eifect of said antenna with respect to space radio waves, said means comprising a second vertical conductor in proximity to said first vertical conductor and connected thereto, the upper portion of said conductor being insulated from said antenna and forming therewith a transmission line having an impedance at the top dependent in value upon the connection'between said conductors,

and means to vary said connection relative to the dimensions of said conductive area to produce a desired current distribution along said antenna.

9. In combination, an antenna comprising a vertical conductor having a conductive area at the top utilized solely to increase the capacitance between the top of said antenna and the'earth, and a connection to earth at the bottom, and means to increase the effect of said antenna with respect to space radio waves while said conductive area is maintained constant, said means comprising a second vertical conductor connected to said first mentioned conductor and having its upper portion insulated therefrom, said two conductors forming a transmission line having an inductance at the top neutralizing at least partially the capacity between said conductive area and the earth.-

10. The combination, in an antenna, of a vertical conductor having a length less than one half of a wavelength of the wave at which said antenna operates, a conducting surface located at the top of said vertical antenna and utilized solely to increase the capacitance between the top of said antenna and the earth, a second vertical conductor parallel with said antenna and spaced in proximity thereto, and a connection between said two conductors at such a point that said two conductors cooperate to produce a maximum of current on said antenna at a point higher thereon than said maximum would occur were said second conductor not employed.

11. The combination, in an antenna, of a vertical conductor having a length less than one half of a wavelength of the wave at which said antenna operates, a conducting surface located at the top of said vertical antenna and utilized solely to increase the capacitance between the top of said antenna and the earth, a second vertical conductor parallel with said antenna and spaced in proximity thereto, and means utilizing said second conductor to produce a maximum of current at a point higher on said antenna than a maximum of current would occur were said conductor not utilized.

12. The combination, in an antenna, of a vertical radiator, a non-radiating capacitance area connected to the top of said radiator, said radiator having a length less than one half of a wavelength of the wave radiated thereby, and means to neutralize a portion of the capacitance between said capacity area and the ground, said means comprising a conductor parallel to said radiator and positioned in proximity thereto, said conductor and radiator being connected together at a point along their length such that the impedance between said conductor and radiator at the top produces the desired capacitance neutralization.

13. The combination, in an antenna, of a vertical radiator, a non-radiating capacitance area connected to the top of said radiator, said radiator having a length less than one half of a wavelength of the wave radiated thereby, and means to neutralize a portion of the capacitance between said capacity area and the ground, said means comprising a conductor substantially parallel with said radiator and means connected between the bottoms of said conductor and radiator to produce an effective inductance between the tops of said conductor and radiator of such a value as to produce said desired neutralization of capacitance.

ROBERT B. DOME.

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