US2344171A - Tower type antenna - Google Patents

Description

Filed April 4, 1942 IRA/$24701? FIGA.

man/5mm? FIGA.

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' INVENTOR 4/5 V 4. F075 TTORNEY Patented Mar. 14, 1944 TOWER TYPE ANTENNA Melvin A. Rote, Newark, N. J assignor to Federal Telephone and Radi tion of Delaware 0 Corporation, a corpora- Application April 4, 1942, Serial No. 437,639

13 Claims.

This invention relates to antenna systems and more particularly to a novel feeding system for antennae.

In Patent No. 2,287,220, issued June 23, 1942, to Alford, is disclosed a new type of antenna structure wherein high frequency energy is supplied to the antenna by feeding energy directly to a capacity area or other unsymmetrical coupling means arranged at one end of the radiant acting antenna structure. The circuit is then completed by coupling the other line to the lower end of the tower or to ground if the tower is grounded.

One defect of such antenna structures is found in that the feeding line is arranged within the surrounding antenna structure and has the impedance characteristic of a concentric transmission line. The impedance of such a line does not match the impedance at the feed point with a resulting loss of energy. Also this feed line radiates and so does not produce the desired current distribution in the antenna.

In accordance with my invention I provide a feeder system for an antenna of the type discussed above which comprises a balanced line which extends substantially to the end of the antenna, the two conductors being then connected to unsymmetrical parts of the antenna, and a means being provided to couple the balanced line to this unbalanced load and to match the impedances without destroying the balance in the line. This construction has the further advantage in structures wherein the upper portion is insulated and used as the radiating part of the antenna, that the feeder will not couple together the insulated parts of the mast as no unbalance current is present.

One arrangement according to my invention utilizes a two conductor balanced line to feed the antenna and the provision of a network-arranged in the line at a point adjacent an end of the antenna. This network may conveniently be one of the type illustrated in a patent to Andrew Alford, U. S. No. 2,165,086, issued July 4, 1939.

A better understanding of my invention may be had from the particular description thereof made with reference to the accompanying drawing in which:

Figure 1 is a diagrammatic side elevation partly in section of a tower type antenna embodying the invention;

j Figure 2 is a diagrammatic side elevation of a dipole antenna embodying the invention, with parts broken away; 4

n a l Figure 3 is a diagrammatic side elevation of a different type of tower antenna, and

Figure 4 is a diagrammatic central vertical section through the upper part of a different form of dipole.

In Figure 1 is shown a tower typeantenna having a radiating portion Ill, supported on insulators II on a supporting tower portion I2. At the top of the radiant acting portion ID of the tower is provided a capacity area [3 spaced from the far end of the tower by insulating element Ia. Energy from a high frequency translator I5 is fed from a point near the feeding end of the antenna over a balanced line IE, to a point near the far end thereof. The conductors of line It must be coupled to capacity area l3 and radiating portion l0, and it is clear that these elements constitute an unbalanced or unsymmetrical load or connection. Accordingly, if the two conductor transmission line were directly connected thereto, its balance would be upset.

In order to provide for preservation of the balance of line I6, I arrange a network indicated generally at I1 at the upper end of transmission line l6. This network I! is of such construction as to provide a coupling between the unbalanced load and the balanced line, and still preserve the balance within the line. The network, preferably, is of the type disclosed in the United States Patent to Andrew Alford No. 2,165,086. In this patent it is demonstrated that if .two impedances are arranged one in series with the line and the other across the line, these impedances being of equal value and the same sign, and a third impedance is connected to a grounding point, the third impedance being of opposite sign to the first named pair of impedances and equal to onehalf the value thereof, the line will remain balanced Network I! meets with these requirements in that condensers l8, and [9A, are connected one in series with the line and the other across the line, and inductance i1 is connected from the conductor having the series condenser to capacity area l3 which serves as the effective F termination or ground for the line. Thus this network provides means for maintaining the balance of line 16 while coupling the line to the unsymmetrical load l3 and ID.

The two conductor transmission line, such as shown at 16, is preferable to a single conductor connected to the capacity area for feeding the energyto the unit.

Referring to Fig. 1 a typical tower antenna would be constructed as follows: the radiating portion In would be approximately M4 long and insulated at H. This would produce a current loop at the top of the tower at which point the ground side of the coupling network is connected.

The capacity hat, required to produce a balance in the transmission line, is smaller with the above connection than when the hat is used for ground connection for the coupling network.

The height of the supporting tower l2 in general would be greater than M4 depending upon the shape of the radiation pattern desired. It is to be pointed out that it is not the magnitude of the impedance of the concentric line formed by the tower and the conductor that governs the current distribution on the tower; however, the single conductor feed line radiates and thus the field pattern is a result of the relative magnitudes and distributions of the currents in the line and tower. By the use of a non-radiating balanced transmission line feed full advantage may be taken of inverted current distribution obtained when a sectionalized antenna tower is fed at the top.

Although the impedance effect of the transmission line is improved by use of a two conductor feeder it should be noted that any unbalance in line It results in loop current therein. Accordingly, in a mast structure such as shown in Figure l, considerable coupling between the radiating portion Ill and the supporting portion [2 will be made through the line IB due to the unbalanced currents therein. By the use of networks such as shown in Figure 1, this harmiul coupling effect may be substantially eliminated. As a result the only coupling effect remaining between the portion Ill and the portion l2 of the mast is the capacitive effect across insulators II.

It is clear that instead of being a solid conductor section as shown in Figure 1, mast l0, 12, may be of open lattice work or any other type desired. Likewise, the principles of my invention would apply as well to other tower structures than the tapered form shown in Figure 1.

In Figure 2 the principles of my invention are shown applied to a dipole radiator unit. As more fully pointed out in previously mentioned Patent No. 2,287,220, various types of antenna units may be provided. The dipole unit of Figure 2 corresponds to one of the types set forth in said patent. The dipole unit itself consists of a tubular rod conductive arrangement ill) provided at each end with separate capacitive coupling elements 23, 23a. The high frequency translator I5 is coupled over a transmission line It to. a further feeder line 2|. The supporting mast 22 serves to house the line and to support the dipole antenna structure 20. At opposite ends of feeder 25 are provided networks I"! and Ha corresponding in all respects to the network I! of Figure 1. Thus, this arrangement serves to maintain the balanced current in lines It and 2|. It should be clear that the dipole shown in Fig ure 2 is only by way of illustration and that the principles of my invention apply to various other forms of dipole antennae. In fact, the principles of this invention apply to any antennaarrangement in which the coupling between a balanced line arranged within the hollow conductive antenna and an unsymmetrical pair of elements at the other end, is necessary. I

In-Flgure 3 is illustrated another embodiment of my invention in which the high frequency energy from translator I5 is radiated from wires 31 attached to-the upper end and arranged all around the periphery of conductive mast 30, in-

stead of from the mast itself. This arrangement provides effectively a radiation which is inverted in pattern with respect to a system wherein the mast itself radiates. This particular type of antenna structure is not a feature of the invention but is shown as a further illustration of an application of the principles of my invention. The network 11 is shown here provided with inductive impedance elements l8b, I80, instead of the capacitive units it and idea of Figure 1. In this .case the capacitive element i9a, must then be made equal to half the impedance value of either of the units l8b, or #80, taken by themselves.

It should be clear that the arrangement of Figure 3 wherein a folded radiating unit is provided, may be applied just as well to the solid mast structure of Figure 1 and to the dipole antennae as to the lattice type of mast shown in Figure 3. Likewise, if desired, a tower 30 may be insulated from the ground, instead of being directly grounded as shown herein. Similarly, if a difierent type of radiation pattern is desired, the mast shown in Figure 1 may be directly grounded and not provided with the insulating plates shown in that figure.

While I have shown in the previous figures an arrangement in which the unsymmetrical coupling elements constitute a capacity area and the antenna conductor, other forms of unsymmetrical units may bepresent and my invention is equally applicable to these. In Figure 4;, is illustrated an embodiment constituting a dipole antenna unit similar to that shown in Figure 2, except that in place of capacity areas such as shown in that figure, separated loop connections between the central conductor and the outer ends of the dipole are provided at 4!, 32. In this instance then, the network Ila may be applied in the same way as in previously mentioned Figure 2. If desired insulating covers d3, 44 may be provided to protect the. antenna loops from atmospheric conditions such as sleet.

It should be understood that the coupling arrangement such as shown in Figure 4 may be used in the case of tower antennae to the same extent if desired. Furthermore, any of various types of antenna units not shown in the drawings may be substituted for those illustrated. In fact, any of various types of antenna arrangements illustrated in the above-mentioned copending application may be provided and the principles of my invention are applicable to all of these forms. The network arrangement can be applied in any instance where balanced feed is required to achieve the desired impedance value and an unsymmetrical connection must be made at the far end thereof.

What is claimed is:

1. A radio antenna comprising a hollow conductive means extending from a position adjacent a feeding point'to a distant point, said hollow conductive means being provided at said distant point with unsymmetrically coupled elements, a balanced conductor feeder means extending within said hollow 'conductor means to said distant point, andmearisfor preserving the balance of said'line while serving to couple the conductors of said line to said'unsymmetrical coupled elements.

2. A radio antenna according to claim 1, wherein said unsymmetrical. coupled elements comprise said hollow conductor means and capacity means spaced from the distant end ofsaid hollow conductor means.

3. A radio antenna system comprising a hollow conductor means extending from a position adjacent to a feeding point to a distant point, a capacity element spaced in insulated relation slight- 1y" beyond the distant end of said conductor means, a balanced two conductor feeder means extending from said feeding point substantially to said distant point, and means for preserving the balance of said line while serving to couple one conductor of said line to said capacity element and the other conductor of said line to said distant point.

4 A radio antenna according to claim 3 wherein said hollow conductor means comprises a plurality of conductors arranged longitudinally in an annular series.

5. A radio antenna according to claim 3 wherein said means for preserving balance of said line comprises two impedance elements of equal impedance value and like sign connected respectively in series in one of the conductors of said line and between said conductors of said line and an impedance of half said equal value impedance and of opposite sign in series in the line with said first named impedance.

6. A radio antenna according to claim 3, wherein said hollow conductor comprises a radiating mast structure mounted directly on the earth to produce a direct ground, and outer conductive means galvanically connected to the upper end of said mast structure and extending downwardly therefrom in spaced relation from said mast and said earth, and wherein said means for coupling comprises a capacity means mounted on the top of said mast structure.

'7. A radio antenna according to claim 3,

wherein said hollow conductor means comprises a central hollow conductor member and an outer conductive means galvanically coupled to the outer end of said hollow conductive means and extending back toward the feeding point in spaced relation with respect to said hollow conductive means.

8. An antenna structure comprising a hollow tower type antenna having a grounded portion and an upper radiant acting portion insulated from said grounded portion, capacity means spaced above said upper portion and capacitively coupled therewith, a two wire transmission line arranged within said hollow antenna and coupled at one end to a balanced high frequency translator, the wires of said transmission line being connected at their other end one to said radiant acting portion and the other to said capacity means, whereby the balance of said line tends to be up set and coupling between said grounded portion and said upper portion of said antenna tends to take place, and means for preventing said balance upset including a network in said transmission line at a point above said grounded portion, said network comprising impedance elements of the same magnitude and sign connected in series in one conductor and between said conductors respectively, and an impedance of opposite sign and one half the magnitude of said first named impedance elements, connected in series in said line with said capacity means.

9. An antenna structure comprising a hollow tower type antenna, capacity means spaced above said antenna and capacitively coupled therewith, a two wire transmission line arranged within said hollow antenna and coupled at one end to a balanced high frequency translator, the wires of said transmission line being connected at their other end one to the upper end of said antenna and the other to said capacity means, whereby the balance of said line tends to be upset, and means for preventing said balance upset including a network in said transmission line at a point adjacent said upper end of the antenna, said net work comprising impedance elements of the same magnitude and sign connected in series in one conductor and between said conductors respectively, and an impedance of opposite sign and one half the magnitude of said first named impedance elements, connected in series in said line with said capacity means.

10. An antenna structure comprising radiating means including a hollow conductor structure provided at an outer end with unsymmetrical coupled elements, and means connected to said elements and extending therefrom through said hollow conductor for feeding said radiating means substantially without interference with radiation therefrom, including a balanced two conductor line and a balancing network in the line adjacent said unsymmetrical elements.

11. An antenna structure comprising hollow radiating conductor means including unsymmetrical coupled elements located at the outer end thereof, a feed line extending through the conductor means and connected to one of said elements, and means for preventing interference with radiation from the conductor means caused by the feed line, comprising a second balancing feed line associated with the first line to form a balanced conductor, extending through the conductor means and connected to the other of said elements, and a network connected to said lines and located adjacent to said unsymmetrical elements, arranged to maintain the lines in balanced condition.

12. An antenna structure as set forth in claim 11, including means for applying to said lines equal currents opposite in phase.

13. An antenna structure comprising a hollow radiating dipole antenna structure including a hollow standard, aligned hollow arms connected to the standard, and unsymmetrical coupled elements at the outer end of each arm, a feed line including a section extending through said hollow arms connected to one of said-elements at the end of each arm and a section extending from said line section through the hollow standard to a source of wave energy; and means for preventing interference with radiation from the antenna caused by the feed line, comprising a second balancing feed line having sections associated with the sections of the first line to form therewith a balanced conductor connected to the other coupled element at each outer end of said arms; and two balancing networks, each connected to said first and second lines adjacent an outer end of an arm, arranged to maintain said lines in balanced condition.

MELVIN A. ROTE.

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