US2112287A - Antenna - Google Patents

Description

UNITED STATES PATENT OFFICE ANTENNA Clarence W. Hansell,

Lindenblad, Rocky Point,

Radio Corporation of of Delaware Application February 3,

12 Claims.

This invention relates to antennas.

A primary object is t of short radio waves w directivity and Wit tivity, maximum radiatio A secondary object is a structure of pleasing appearance simple antenn suitable for use on towers.

Another object i ical antenna arran waves which gives poles energized in to one another.

enable the transmission ith considerable vertical h little or no horizontal direcbut at the same time giving uniform and n in the horizontal plane.

to provide a mechanically the tops of high buildings and s to provide a simple mechangement for use with ultra short the equivalent of a series of dithe same phase with respect These and other objects which may appear from a reading of according to the invention, by tenna with a variable series of overlapping con flow from the larger diame diameter end. By suit of each conducting direction.

Advantages tenna (1) pos no horizontal directivity the specification are achieved,

providing an andiameter consisting of a ductive tubes with power ter end to the smaller able design of the length tube,,the currents in the effectubes are made to be in the such an arrangement'there f a series of dipole rent in the same of theinvention are that the ansesses great vertical directivity but when erected vertically;

(2) is simple to construct; (3) rigid in construction; and (4) easily adapted for use on the top of a high building or tower.

In the preferred embodiment of the invention,

each overlapping tube of the invention extends from its free end effective radiating length of the tubes are directly communication wave.

and has an e-half the Alternate onnected together at the exto the roof top, portion equal to on treme end of the outermost ones of the tubes in order to obtain a the currents in the apparatus is connecte the bottom of the anten desired phase relationship of antenna. The high frequency d to the innermost tube at na at a point designed to match the impedance of the connecting feeder.

In another form of the invention, the antenna is comprised of overlapping tubular conductors of different diameters each tube having an effective radiating portion greater than one wavelength and an jacent tube of -half other integral portion less than long set into its next ad- In this case the individual tubes do not extend from their free H ends all the way to the roof top. The overlapping Port Jefferson, and Nils E.

N. Y., assignors to America, a corporation portions in this embodiment may vary in length in order to obtain a desired mutual coupling between adjacent tubes. The effective radiating portions of the tubular conductors need not be exactly of the same length so long as a requisite 5 cophasal arrangement of currents in the various elements is maintained.

The widest diameter tube, which is the lowermost tube when the antenna is erected vertically, in one embodiment is set either on or into theroof top of the building and shielded, and the high frequency apparatus connected to this lowermost tube by means of a feeder at a point designed to match the impedance of the feeder. The shield for the bottom portion of the lowermost radiator or tube should preferably be less than one-quarter wavelength, if the. antenna is mounted above the top of the building. The reasonjfor making the shield for the lower portion of the lowermost radiator of the length hereinabove specified is to prevent the shield from becoming a radiator for the working wave. However, if the base of the antenna is set into and below the roof top, then the shield for the lowermost radiator should preferably be exactly one-quarter of a wavelength since the shield in this case cannot now be externally excited because its external surface is shielded by the metallic roof top.

In the accompanying drawing:

Figs. 1, 2 and 3 illustrate three different embodiments of the invention, and

Figs. 4 and 5 illustrate the equivalent circuits of Figs. 2 and 3, respectively.

Referring to Fig. 1 in more detail, there is shown mounted on a roof top of a tall building a vertical antenna constructed in accordance with the preferred embodiment of the present invention. This antenna comprises a series of overlapping tubular conductors a, b, c, d, conductor a of which i may, if desired, be a linear rod or wire. Connected to the bottom portion of conductor a by means of an adjustable tap e is shown a feeder line connected to high frequency apparatus indicated conventionally in box form. Tap e is so adjustedthat the impedance of the feeder con- 5 necting with the high frequency apparatus matches the impedance of the conductor a and the antenna to which the feeder is connected. Top conductor a continues straight through the antenna as a transmission line.

Each conductor a, b, c, d, has an effective free radiating portion which is one-half the length of the operating wave and which portion extends beyond the next adjacent overlapping tube. In

electrical order to obtain the proper phase relations of the the length of the operating wave.

current in each tube, the free ends of conductors c and d are respectively directly connected to their alternately located conducting tubes. Thus, as shown in the drawing, the free end of tube d is connected to conducting tube b, and the free end of tube is connected to conductor a. In this manner the various tubes are made to be the equivalent of a series of dipoles and the voltage distribution therein is equal throughout the antenna and substantially as indicated by the dotted lines, which show that the currents in all the effective radiating portions of the tubular conductors a, b, c and d are in phase.

To prevent undesired radiation from the lowermost portion of the largest diameter tube (1 there is provided a shield 1 which is one-quarter of the length of the operating wave and surrounds this lowermost portion of d. Rain shields prevent water from entering the openings of the tubular conductors, and stiffening insulators maintain the tubes in proper concentric relation to one another. These insulators are mounted at voltage nodal points on the conductors to avoid energy dissipation; i. e., at points onequarter of a wavelength from the free end of each tube. In this manner there is obtained a rigid structure of minaret shape which possesses great vertical directivity and little or no horizontal directivity.

Figs. 2 and 3 illustrate other forms of the minaret type of antenna which may be used. In Figs. 2 and 3 each conductor a, b, 0' etc., and a", b", 0'', etc., is mounted on an insulator and supported upon its immediately adjacent and partly overlapping tubular conductor. Thus, conductor a is supported by conducting tube b, and a" by conducting tube b".

In Fig. 2, in order to make the currents in the eifective radiating portions of the conductors be in the same direction, these radiating portions are each made to be greater than one-half wavelength, and the lower portion of each conducting tube which is set into its next adjacent lower conductor is made to be less than one-quarter of The lengths of these portions, although following the law stated above, are not necessarily the same but vary somewhat, as indicated by the numerical characters which give the dimensions of an actual embodiment successfully operated to work on a wavelength of 150 cm. The exact lengths are obtained by measuring the energy radiated at a distant point and varying these lengths until maximum response is obtained. In other words, the lengths of the efiective portions depart from one-half wave and the mutual coupling set-in portions depart from one-quarter wave so as to obtain a desired phase: relation between adjacent sections of tubes. Fig. 4 shows the equivalent electrical circuit of the system of Fig. 2. It will be apparent from an inspection of Fig. 4 that a conducting system as shown, which is greater than one-half wavelength is equivalent to a capacitor and one which is less than one-quarter wavelength is equivalent to an inductor.

Fig. 3 shows a similar arrangement except that here the effective radiating portion of each conductor of the antenna is less than one-half wavelength and the set-in portion is greater than one-quarter wavelengt Fig. 5 shows the equivalent electrical circuit of the system of Fig. 3. It will be evident from an inspection of Fig. 5 that a conducting system as shown in Fig. 3, which is less than one-half wavelength, is equivalent to an inductance and one which is greater when made longer.

than one-quarter wavelength is equivalent to a capacitance.

From what has gone before it will be apparent that a conductor shorter than a half wave conductor and one shorter than a quarter wave conductor are both inductances when looked upon from a parallel circuit standpoint; i. e., inductance and capacitance in parallel. Similarly, these conductors are equivalent capacitances When such a circuit is of correct length, the parallel impedance (resistive) is very high if the resistive losses in the circuit are low. If we depart from the tuning point an infinitesimal value, the impedance, while still high, is either inductive or capacitive, depending upon conditions already set forth. The more we depart from the tuning point, the lower is the reactive component of the impedance. The impedance thus becomes predominantly reactive and of low value.

Figs. 2 and 3 sufier from the disadvantages of possessing a tapered voltage distribution and requiring the high frequency apparatus to be connected to the outside of the lower suspension member; for which reason, among others, it is preferred to use the system of Fig. 1.

It will be understood, of course, that the invention is not limited to the precise arrangement shown in the figures, since various modifications may be made without departing from the spirit and scope thereof. For example, the antennas of Figs. 1, 2' and 3 may be extended symmetrically from a center so as to form a structure equivalent to two antennas end to end, somewhat like an extended dipole antenna. Also, various arrays of antennas may be used to obtain additional directivity.

What is claimed is:

1. An antenna for enabling the radiation of short radio waves with directivity in the plane of said antenna and with substantially uniform radiation in the plane at right angles to said antenna, comprising a plurality of coaxially arranged electrically conductive sections of different diameters, said diameters decreasing progressively in size toward the free end of said antenna, the effective portions of said sections being of such length and said sections being so coupled together that said portions are energized in the same phase with respect to one another.

2. A vertical transmitting antenna for enabling the radiation of short radio waves with vertical directivity and with substantially uniform radiation in the horizontal plane, comprising a plurality of coaxially arranged electrically conductive sections of different constant diameters, said diameters decreasing progressively in size toward the free end of said antenna, the effective portions of said sections being of such length and said sections being so coupled together that said portions are energized in the same phase with respect to one another.

3. A rigid, short wave antenna adapted for use on the top of a high building comprising a plurality of coaxially arranged cylindrical conductive sections of different diameters coupled together, said diameters progressively decreasing in size toward the free end of said antenna, each section being for an appreciable portion of its length set into its adjacent larger section for obtaining a desired mutual coupling between sections, whereby the effective portions of said sections are all energized in phase with respect to one another.

4. An antenna in accordance with claim 3,

characterized in this that the portion of each section set into its adjacent section is less than one-quarter of the length of the operating wave, and the effective radiating portion of each section is greater than one-half the length of the operating wave.

5. An antenna comprising a plurality of coaxially arranged metallic cylindrical sections of diiferent diameters coupled together, said diameters progressively decreasing in size toward the free end of said antenna, each section being for an appreciable portion of its length set into its adjacent larger section for obtaining a desired mutual coupling between sections, and a feeder line coupling high frequency apparatus to the largest diameter section of said antenna at a point on said last section matching the impedance of said line, whereby the effective radiating portions of said antenna are energized in phase with respect to one another.

6. An ultra short wave vertical transmitting antenna comprising a plurality of coaxially arranged electrically conductive cylindrical sections of different diameters coupled together, said diameters progressively decreasing in size toward the free end of said antenna, each section being for an appreciable portion of its length set into its adjacent larger section for obtaining a desired mutual coupling between sections, such that the effective portions of all sections are energized in phase with respect to one another, and a feeder line coupling high frequency apparatus to the smallest diameter section of said antenna at a point on said last section near the base of the largest diameter section, whereby directivity in the plane of said antenna and substantially uniform radiation-in the plane at right angles to said antenna is obtained.

'1. In an antenna, the method of obtaining substantially uniform radiation in a plane at right angles to the axis of the antenna, which includes progressively decreasing abruptly and in steps the diameter of said antenna toward its free end in predetermined fashion so as to obtain a desired mutual coupling between adjacent sections of antenna, and producing a flow of power toward said free end.

8. A rigid, vertical, short wave antenna comprising a conductor, a second conductor in the form of a tube surrounding the lower portion of said first conductor for an appreciable fraction of the length of said first conductor, and a third conductor also in the form of a tube surrounding the lower portion of said second conductor for an appreciable fraction of the length of said second conductor, whereby said antenna progressively decreases in diameter from its base toward the free end of said first conductor, high frequency translating apparatus coupled to the base of said antenna, the effective unsurrounded portions of said conductors having such lengths and being so coupled to one another that said effective portions are all energized in phase with respect to one another.

9. An antenna in accordance with claim 8, characterized in this that the effective radiating portions of said first conductor not surrounded by said second conductor, and said second conductor not surrounded by said third conductor are equal to one-half the length of the communication wave.

10. An antenna in accordance with claim 3, characterized in this that the portion of each section set into its adjacent section is greater than one-quarter of the length of the operating wave, and the effective radiating portion of each section is less than one-half of the length of the operating wave.

11. A vertical transmitting antenna for enabling the radiation of short radio waves with vertical directivity and with substantially uniform radiation in the horizontal plane, comprising a plurality of coaxially arranged, electrically conductive sections of different constant diameters, said diameters decreasing progressively in size from the base toward the free end of said antenna, the effective radiating portions of said sections each having a length approximately equal to half the length of the communication wave, said sections being so coupled to one another that they are energized in the same phase.

12. A rigid, vertical antenna comprising a plu-' rality of coaxially arranged cylindrical sections of different diameter, the diameters of said sections progressively decreasing in size from the base toward the upper end of said antenna, each section surrounding the next inner adjacent section for an appreciable portion of the length of said next inner adjacent section, means directly connecting alternate sections together, said sections each having an effective radiating portion of a length equal to half the length of the op eratlng wave, whereby all of said effective portions are energized in phase, and high frequency translating apparatus coupled at the base of said antenna to the innermost cylindrical section. CLARENCE W. HANSELL. N S E. LIN J E .Dv

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