US2017047A - Directional antenna arrangement - Google Patents

Description

O ct. 15,1935. c. w. HANSELLY 2,017,047v

DIRECTIONAL ANTENNA ARRANGEMENT I I Filed March 11, 1932 2 Sheets-Sheet 1 I290 r N {I mMwW/M 7 I 5' W [Ma/4mm maz/umes\ E I I I I I I I l I I I I I I l I I mil/530777176 INVENTOR c.'w. HANSELL ATTORNEY @ct. 15,1035 w HANSELL 2,017,047

DIRECTIONAL ANTENNA ARRANGEMENT Filed March 11, 1932 2 Sheets-Sheet 2 ENVENTOR C W. HANSELL BY gm ATTORNEY Patented Oct. 15, 1935 UNITED STATES PATENT OFFICE DIRECTIONAL ANTENNA ARRANGEMENT Application March 11, 1932, Serial No. 598,124

10 Claims. (01. 250-33) This invention relates to improvements in directive antenna systems.

It has been found that when a wire having a length which is relatively long with respect to the length of the communication wave is excited in such fashion that standing waves are produced thereon, that radiation occurs principally in the direction of symmetrical cones having their apices at the center of the wire.

It is an object of the present invention to utilize this phenomena for the directional radiation or reception of electromagnetic energy.

More specifically, it is an object of this invention to provide an antenna system for communication with stations located in two different directions and so designed as to engender a substantial increase in the energy transmitted to or received from these stations as compared with a non-directional system. This is accomplished by providing a directive antenna system comprising two parallel wires placed one above the other.

These wires are arranged to be energized in such a manner that the current in one wire will be in leading or lagging quarter phase relation with respect to the current in the other wire. The particular quarter phase relation is determined in a way to be explained later. By staggering the ends of the wires in a novel manner the radiation in one general direction along the axis of the wire is substantially cancelled while in the opposite general direction there is obtained a double lobe of radiation.

One advantage of this invention is that the system requires only two main supporting poles, the same number which is required for a single wire or for a half wave dipole. Consequently, the cost of erecting such a system is not very great.

A better understanding of the invention may be had by referring to the accompanying drawings, wherein Figure 1 shows, in elevation, an

antenna system embodyingthe principles of this invention, and Figure 1A shows a plan view of the system of Figure 1. Figure 2 is a polar diagram of radiation in the horizontal plane for a system as shown in Figure 1 having wires 8 wave lengths long. Figure 3 isa polar diagram of the distribution of radiation in a vertical plane passing through the antenna wires, for the system shown in Figure 1. Figure 4 is a polar diagram of the distribution of radiation in a plane through the center of the antenna which is inclined upward at an angle of 10 degrees to the horizontal in the general desired direction of radia-- tion. Figure 5 illustrates graphically the expected relative strength of received signal waves ill at different receiving stations located in the general direction of desired radiation, for antennas with two difierent lengths of radiator wires.

Referring to Figure 1 in more detail, there is shown an antenna system comprising two radiator wires I and 2, both wires being supported by the poles or towers 3 and 4, shown in dotted lines. Assuming that the antenna is used for transmission, the radiators are energized from the transmitting apparatus over a circuit through transmission line 5, impedance matching and phase shifting device 6 and feeders 1, 1. Feeders I, I are each arranged in the form of a two wire line to prevent undesired radiation, the two wires of each line being adapted to carry substantially 15 equal and opposite currents so that their radiations are opposite and cancel out to a very low value.

To obtain substantially equal and opposite currents in the wires of a pair it is necessary that the antenna radiator be fed at a peak of potential or maximum impedance point. This is effected by making the length of the radiator wires an integral number of half wave lengths minus a certain end correction. Both wires of the feed line then 25 have the same type of reflection at the antenna end. In addition, the two wires have equal and opposite voltages impressed upon them in the impedance matching device 6.

The impedance matching and phasing equip- 30 ment 6 will not be described herein since such devices are well known in the art and, of themselves, form no part of the present invention.

The energies fed to radiators I and 2 are so adjusted that substantially equal currents are developed in the two and the phase diiference between the currents is preferably degrees. The system may be operated, if desired, with a somewhat different phase relation without departing from the spirit of the invention, al- 40 though. in such case, the directional characteristic will be somewhat altered and it may then be desirable to change the relative positions of the radiators. It is preferred, however, to use the 90 degree phase relation between the currents in 45 the two wires and the following description of the system will, therefore, be based on an assumed 90 degree phase difference.

The novel radiation characteristic of the system is obtained by so positioning the two radiator 5 wires that their radiations are in phase and add in two desired directions of radiation, but are out of phase so that they add imperfectly or tend to cancel one another in other directions.

In Figure 1, wires I and 2 are shown arranged 55 length for the waves radiated.

to carry equal quarter phase currents. These Wires are so positioned that their radiations add in two desired directions to produce main beams of radiation of the type illustrated in Figures 2, 3, and 4; a characteristic attained when the projection of a line joining the centers of the two radiators upon the two desired directions of radiation is an odd .multiple of a quarter wave Assuming that it is desired to obtain two main beams of radiation in the general direction away from the transmitter, as shown in Figure 1, then the phase of the current in wire 2 is arranged to lead that in wire I by 90 degrees, and the projec tion of the line joining the centers of the two radiators upon the desired directions of radiation is made to be an odd multiple of a .quarter wave, such as 1, 5, 9 or 13 etc. quarter waves. If the phase of current in wire 2 lags that'in wire l by 90 degrees, the projection of the line between centers of the radiators upon the desired directions of radiation is again an odd multiple of a quarter wave, but this time 3, 7, 11 or 15 etc. quarter waves.

Similarly, if it is desired to obtain two main beams of radiation in the general direction toward the transmitter, as shown in Figure l, the phase of the current in wire 2. is arranged to lead that in wire l by 90 degrees, but the projection of the line between centers of the radiators upon the desired directions of radiation should now be 3, 7, 11 or 15 etc.,quarter waves. If the phase of current in wire 2 lags that in wire I by 90 degrees the projection of the line between centers of the radiators upon the desired directions of radiation is made to be 1, 5, 9 or 13 etc. quarter waves.

When the two radiator. wires are so positioned that their radiations add in the two desired directions of radiation the directive characteristics of radiation in the undesired directions may be varied by moving the center of one wire relative to the other along a line in the plane of the wires which is at right angles to the desired directions of radiation. In general, the best position is obtainedwhen the main beam of radiation in the reverse general direction, which is inclined upward from the direction of the wires, is most nearly balanced out. It is to be distinctly understood, however, that this invention is not limited in application to this particular position since, for practical reasons, it may be advisable to utilize other positions under certain circumstances.

Although it is not essential, it is preferred to make the vertical spacing between the radiator wires not less than a quarter wave length for the waves to be radiated. Increasing the spacing between the wires, in general, decreases the direct coupling between them and makes it easier to adjust the phase and strength of the current in the two radiators. However, there will be optimum spacings at which the coupling between the radiators passes through minima. These minima are obtained when the longitudinal displacement of the wires, with respect to one another, is approximately a quarter wave length or an odd multiple of a quarter wave length. Longitudinal displacements which fulfill this condition for minimum coupling between the radiators may be obtained, without changing the addition of radiation in the desired direction, by adjusting the center of one radiator, relative to the other, along the line in the plane of the wires which is at right angles to the desired directions of radiation, until the radiators have a longitudinal displacement or stagger corresponding to minimum mutual coupling.

In practice, antennas arranged according to the principles of this invention will not be designed for minimum couplingbetween radiators, but will be designed to effect a compromise among a number of factors which include besides this coupling, desired directive characteristics, mechanical limitations, cost, etc.

From a commercial and economic standpoint it has been found that a system designed in accordance with the present invention is most effective when the angle between the two principal desired directions of transmission or reception is between 10 and 40 degrees. Experience and calculations have shown that the radiation which is most effective at a distant receiver, is that which leaves the transmitting antenna at a small angle to the earth. Horizontal radiation is of little value for long distance transmission because absorption and reflection from the surface of the earth make it impossible to obtain much true horizontally directed radiation. On the other hand, the higher angle radiation is ordinarily ineffective in reaching the receiver so that, from this standpoint, it is desirable to keep the beam directed at as low an angle as possible. In practice, the optimum compromise is obtained if the antenna is designed to radiate maximum energy at an angle of from 7.5 to 15 degrees from the horizontal. Ordinarily, it is preferred to design the antenna to radiate maximum energy at an angle of about 10 degrees from the horizontal.

A horizontal wire 8 wave lengths long produces lobes or maxima of radiation which differ in angle by 35 degrees in the horizontal, but by about 30 degrees in the plane inclined upward at 10 degrees in the general desired direction of transmission. At 17 degrees elevation the two lobes or maxima merge into one. Figure 4 shows the directive characteristics obtained in a plane inclined at 10 degrees to the horizontal for one design of this new type of antenna.

Figure 5 shows the relative intensity of radiation obtainabie with two difierent designs of antennae according to the present invention, when used to fit a particular need, such as one which has arisen in commercial practice in communicating from New York to Central and South America. In this figure, curves are shown for antennas with radiator lengths of 6 and 8 waves respectively. The abscissa or angle from the antenna axis corresponds to the angle on either side of the plane of the radiator wires to the distant receiving stations. The ordinate is plotted in values corresponding to relative received energy.

It is to be understood, of course, that various modifications may be made in this invention without departing from the spirit and scope thereof. For example, a combination of two or more of the antennas, such as has been described, may be used with such positions and phase relations of currents that their radiations add in the desired directions and more perfectly suppress radiation in undesired directions.

I claim:

1. An antenna arrangement comprising an approximately horizontal single wire antenna, a refiector comprising a single wire parallel to said antenna wire and spaced therefrom a vertical distance substantially equal to a quarter wave length, both said wires being staggered, said stagger being equal to an odd multiple of a quarter wave length in the desired direction of transmission, and means for .energizing said wires substantially 90 degrees out of phase with respect to each other.

2. An antenna arrangement for obtaining directivity in two different directions which form an acute angle with respect to each other comprising a single pair of substantially equal length wires consisting of an approximately horizontal antenna wire and a reflector wire parallel to said antenna wire and spaced therefrom vertically a distance at least equal to a quarter wave length, the projection of the line joining the centers of the two wires upon the desired directions of radiation being made an odd multiple of a quarter Wave length, energy feed lines connecting both said wires to high frequency apparatus, means for energizing said wires substantially 90 degrees out of phase with respect to each other over said feeders, and means for cancelling radiation from said feeders.

3. An antenna arrangement for obtaining directivity in two directions which form an acute angle with respect to each other, comprising a single pair of substantially equal length wires consisting of an approximately horizontal wire and a reflector wire parallel to said horizontal wire and spaced vertically a distance away, the projection of the line joining the centers of the two wires upon the desired directions of radiation being made an odd multiple of a quarter wave length, high frequency apparatus, phase shifting apparatus, a pair of transmission lines extending from said high frequency apparatus to said phase shifting apparatus, feeders extending from said phase shifting apparatus to both said wires, and means for cancelling radiation from said feeders.

4. An antenna arrangement for obtaining beams of radiation in two different directions comprising an approximately horizontal single wire antenna, a reflector wire parallel to said horizontal wire and spaced vertically a distance away, said two wires being of substantially equal length, the projection of the line joining the centers of the two wires upon the desired directions of radiation being made an odd multiple of a quarter wave length, and means for energizing both said wires out of phase with respect to each other.

5. A transmitting station for transmitting simultaneously in two different directions which form an acute angle having, in combination, a radio transmitter, an antenna system comprising two parallel radiator wires each being long with respect to the working wave length, said wires being in a vertical plane, their centers being separated by a distance which has a projection upon the two desired directions of transmission equal to an odd multiple of a quarter wave length for the waves to be radiated from the antenna, and transmission lines between said transmitter and antenna for energizing the two radiator wires to carry currents 90 degrees different in phase.

6. An antenna system comprising, in combination two mechanical supports, two parallel radiator wires suspended between the supports each being long with respect to the working wave degrees difierent in phase, the displacement be- 5 tween the centers of the two radiator wires being such that maximum beams of radiation are obtained in two different directions corresponding approximately to the directions required for most efiicient communication with two distant, separated stations or groups of stations.

'7. An antenna arrangement for obtaining beams of radiation in two different directions, which directions form an acute angle, comprising an approximately single wire antenna, a reflector wire parallel to said antenna wire and spaced vertically a distance away, said wires having lengths approximately equal to an integral number of half wave lengths at the operating frequency minus an end correction, the projection of the line joining the centers of said two wires upon a desired direction of radiation being equal to an odd multiple of a quarter wave length, said wires being adapted to be energized out of phase with respect to each other.

8. An antenna arrangement for obtaining beams of radiation in two different directions, which directions form an acute angle, comprising an approximately single wire antenna, a reflector wire parallel to said antenna wire and spaced vertically a distance away, said wires having lengths approximately equal to an integral number of half wave lengths at the operating free quency minus an end correction, the projection of the line joining the centers of said two Wires upon the desired directions of radiation being equal to an odd multiple of a quarter wave length, and means for energizing said wires to have equal and opposite voltages, said means being connected to said wires at points of maximum impedance.

9. An antenna arrangement for obtaining beams of radiation in two different directions comprising an approximately horizontal single wire antenna, a reflector wire parallel to said horizontal wire and spaced vertically a distance away, said two wires being of substantially equal length, the projection of the line joining the centers of the two wires upon the desired directions of radiation being a multiple of a quarter wave length, and means for energizing said wires to have equal and opposite voltages, said means being connected to said wires at points of maximum impedance.

10. An antenna arrangement for obtaining beams of radiation in two different directions comprising an approximately horizontal single wire antenna, a reflector wire parallel to said horizontal wire and spaced vertically a distance away, the projection of the line joining the centers of the two wires upon the desired directions of radiation being made an odd multiple of a quarter wave length, and means for energizing both said wires out of phase with respect to each other.

CLARENCE WESTON HANSELL.

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