US2157159A - Antenna system - Google Patents

Description

May 9, 1939. H BROWN 2,157,159

ANTENNA SYSTEM Filed'March 24, 19:57 2 sheets-sheet 2 Snnentor y Gqrge II. Brown Gttorneg Patented May 9, 1939 i 2,1579l5i UNITED STATES LPATENT OFFiCE ANTENNA SYSTEM George H. Brown, Haddonfield, N. J., assigner to Radio Corporation of America, a corporation of v Delaware Application March 24, 1937, Serial No. 132,679 Claims. (Cl. 250-33) My invention relates to antennas. More paran antenna system of the character illustrated ticularly, my invention has for its purpose to in Figure 1C; and provide means for energizing co-linear juxta- Figure 3 illustrates one practical embodiment positioned antennas. In one form, by invention of my invention. 5 is applied to a plurality of vertical half-wave In Fig. 1A, vertica1,co1inear, end to end half- 5 antennas placed end to end in the same straight wave antennas I and 3 are energized by a high line whereby the antennas are fed at their juncfrequency generator E, at the junction of antions. In a modification, I arrange a pair of end tennas I and 3. Assuming that the currents in to end vertical antennas so that they are enerthe antennas are equal, the current distribution gized at their junction and at the base of one in the two antennas I, 3 is represented by the 10 of the antennas. dash lines 5 and l.

I am aware that a pair of half-wave antennas, Fig. 1B illustrates a pair of co-linear, end to placed end to end in the same straight line and end half-wave'antennas 9 and II, which are enenergized at their base, have a current distribuergized between earth and the base of antenna l5 tion in which the current in one of the antennas I I, by generator E. Assuming that the antennas 15 is out of phase with the current in the other 9, II are each a half-wave length long, and have antenna. The so-called Franklin antenna alternating currents flowing therein, the current overcomes this difllculty of out o phase currents distribution is represented by the dash lines I3 by employing a current phase reversing section and I5. It will be observed that one current I3 between the two antennas. In such Franklin anis of opposite phase with respect to the other, I5. 20

tennas, the currents in the lower radiator are in In Fig. 1C I have illustrated a pair of halfphase with the currents in the upper radiator. wave antennas I1 and I9, which are energized Such an arrangement, while desirable in theory, at two points. One of these points represents the has two practical drawbacks: First, the proper generator E, which is connected at the junction operation of a phase reversing section is neither of the antennas I1, I9. The other generator E' 25 easily obtained nor constant in practice; and is connected between the lower end of antenna I9 second, it is not always desirable to have the and earth. It will be seen that the present syscurrents equal in both radiators. tem represents a combination of the systems il- One of the objects of my invention is to provide lustrated in Figs. lA and IB. The current dismeans for energizing a pair of co-linear end to tribution in the present system (Fig. 1C) is repre- 30 end antennas at a point between said ends. sented by dash lines 2l and 23. These lines rep- Another object is to provide means for imresent the algebraic sum of the currents resultpressing radio frequency currents between the ing from currents impressed by the generators adjacent ends and at the base of co-linear juxtaat the junction of the antennas and at the base positionedv vertical antennas. of one of the antennas.

A further object is to provide means for alter- It will be apparent that as the relative value of ing the ratio of radio frequency currents imthe in phase and out of phase currents in the two pressed in the upper and lower sections of coantennas is changed, the current distribution will linear end to end vertical dipole antennas. be altered. I have found that the effective servo A still further object is to vary the angle of ice area of the antenna and generator system of 40 radiation of a pair of co-linear end to end dipole my invention may be varied by Varying the pro,- radiators. portion of the currents in the two radiatorsA In I propose to achieve these objects and overgeneral, high angle radiation is considered uncome the aforementioned difficulties by means of desirable because such radiation increases :lading my invention, which is more fully described by in the ordinary service area. In certain installa- 45 reference to the accompanying drawings. tions, however, high angle radiation may be de- Figures 1A, 1B and 1C illustrate, respectively, sired. Such radiation may be controlled, as will the current distribution in co-linear juxtaposihereinafter be described. tioned half-wave length vertical antennas in In Fig. 2A, I have represented the angle of ,-,0 which currents are fed at the junction of the radiation by 1, and the electric eld by F. In 5r two antennas, between one of the antennas and Fig. 2B, by a series of graphs, I represent the ground, and at both the junction and the ground relative characteristics which may be obtained connection; by varying the ratio of current in the upper an- Figures 2A and 2B are graphs showing the tenna with respect to the current in the lower angle of radiation and the electrical eld about antenna. If the current in the lower antenna is 55 d3, a coaxial cable or the like.

considered unity, and the current in the upper antenna is represented by M, the curves of Fig. 2B represent ratios from M =-.25 to M F01' the optimum suppression of fading within the ordinary service area, the ratio should equal a value between .5 and .75.

In the practical application of my invention, it will be realized that it would be very diiiicult to energize an antenna which comprises relatively tall radiators, at their mid-points, because of obvious constructional diiiculties. While an ordinary transmission line might be employed, its presence will deleteriously affect the lower radiator. However, I propose to use the lower antenna as a combination of radiator and transmission line, whereby the generator or transmitter may be placed at the base of the antenna, as shown in Fig. 3.

A transmitter 25 is connectedvto a transformer 2'! which includes Va primary 29 and a center tapped secondary 3|. The center tap is connected to the secondary 33 of a transformer 35, whose primary 36 is coupled through the phase control and tuning control network 37, to the transmitter 25.

The center tapped secondary 3|( has its outer terminals connected to a transmission line 39 which comprises a pair of conductors 4| and These conductors terminate in the primary winding of a transformer 35. The primary winding has a center tapped terminal which is connected to the secondary coil 4l. The secondary coil in turn is connected to a half-wave radiator 49, which may be either a single conductor or, for purposes of symmetry, a pair of conductors 5| and 53. The entire antenna system is preferably supported by a non-conductive mastv55.

Having described the circuits, I shall now briefly describe the operation of the system. Currents from the transmitter 25 are induced in the half-wave transmission line '39, through the transformer 2l. The currents induced in the secondary 3|A ilow in opposite directions through the conductors 4|, 43. These currents induce currents in the secondaryrd'l of the transformer G5. The currents thus induced in the secondary It? flow in the conductors 5|, 53 of the upper antenna and in the conductors 4|, 43 of the lower antenna, just as the currents represented by the dash lines 5, are distributed in the antennas 3 of Fig. 1A.

In order that additional currents may be radiated irom the lower `half-wave antenna section in the same phase with the currents induced by the transformer 45, the phase control and tuning network 31 is adjusted so that the additional currents,.flowing through this network, and induced in the secondary 33 of the transformer 3 are in the proper phase. Since these additional currents in the two conductors '4| and 43 are in the same phase, due to the center tap connection on the secondary 3|, these currents will be radiated from the transmission line 39.

It will be apparent that the coupling between the primary and secondary in each 'of the transformers 21, 35 and 45 may be adjusted to control the ratio of the currents in the upper and lower radiators to thereby yobtain the desired angle of radiation and resulting effective service area about the antenna system.

From the foregoing description, it will be seen that I have described a pair of vertically disposed, co-linear juxtapositioned, half-wave antennas which may be energized at their junction and also between the lower antenna and earth. The ratios of the currents may be regulated to thereby obtain the desired characteristic field about the antenna.

It should be understood that my invention may be applied to vertically arranged systems, or to a horizontal arrangement, or any other angle that may be desired. It should also be understood that while I have shown the invention applied to two radiators of half-wave length each, other numbers of radiators of differing effective lengths may be used.

I claim as my invention:

1. An antenna including in combination a first radiator, a second radiator comprising a two conductor transmission line, means including out of phase currents in the conductors of said second radiator for impressing in phase currents of the same frequencyon said rst and second radiators, and means for varying the ratio of the currents impressed on said radiators to thereby Vary the angle of radiation from said radiators. k

2. An antenna system including a co-linear end to end pair of antenna sections; one of said sections including a transmission line, non-radiating for out of phase currents, for impressing radio frequency currents on the other of said sections; other means for impressing in phase radio frequency currents of the same frequency on the section including said transmission line whereby said second mentioned radio frequency currents may be radiated from said transmission line,l and means for varying the ratio of the radio frequency currents in said sections to thereby determine the angle of radiation from said sections.

3. In an antenna system, a half-wave antenna; a second half-wave antenna being disposed colinearly and end to end with respect to said iirst antenna; said second antenna including a two conductor transmission line carrying out of phase currents for energizing said rst antenna, means for impressing said out of phase currents on said rst antenna in phase; means for impressing said out of phase currents on said second antenna, and including means whereby said currents in said second antenna are in phase in the conductors of said transmission line and in phase with and of the same frequency as the currents impressed on said rst antenna.

4. An antenna system including in combination a pair of half-wave dipole antennas, the i-lrst of said pair including a two conductor transmission line, means for impressing out of phase currents in the conductors on said transmission line, means for impressing said out of phase currents on the second of said antennas, and means for impressing in phase currents in the conductors of said transmission line, said currents being in phase with and of the same frequency as the currents in said second antenna.

5. In a device of the character of claim 4, means for varying the ratio of the in-phase currents in said antennas.

GEORGE H. BROWN.

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