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~ Nov. {5, 1946!.
GJH. BROWN EI'AL
2,4105%
ANTENNA SYSTEM
Filed Oct. 311., 1944
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ANTENNA
SYSTEM
2,191,597
_
Filed Oct. 31, 1944
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' 2 Sheets-‘Sheet 2
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Patented Nov. 5, 1946
21,59?
PATENT‘ OFFICE
2,410,597
ANTENNA SYSTEM
’
'
George H. Brown and Donald W. PetersomPrince
ton, N. J ., assignors to Radio Corporation of
America, a corporation of Delaware
Application October 31, 1944, Serial N 0. 561,189
11 Claims. (Cl. 250-41)
.
This invention relates to antenna systems, and
more particularly to improved directive antenna
systems providing directive patterns in the form
of relatively narrow beams, and operative over
broad frequency bands with high e?iciency.
The principal object of the present invention
is to provide an improved broad band antenna
gineering principles. It is found that high di
rectivity, in view of the number of radiators, and
minimum secondary lobes in the directive pat
radiator elements with power division networks
for apportioning power among the various ele
ments to produce high directivity with minimum *
tern, will be obtained by exciting the outer groups
'
I and ‘l each with 10 percent of the available
power input, and the inner groups 3 and 5 each
with 40 percent of the available input.
The necessary division of power between the
Another object is to provide an improved an
tenna system of the type described wherein the
radiator elements and the power division net
Works may be designed so that the overall system various radiators has been effected heretofore by
maintains a relatively constant impedance
various means, practically all of which will op
throughout a broad frequency band.
erate e?iciently only at the single frequency for
A further object is to provide an improved
which they are designed, owing to the use of
system of the described type which may be de 20 resonant elements such as matching and phasing
signed to employ coaxial transmission lines of’v
stubs in the networks. In accordance with the
standard commercially available impedances.
present invention, power. division is accomplished
These and other objects will become apparent
by networks of the line balance convertor type,
to those skilled in the art upon consideration of
such as that described in copending U. S. appli
the following description, with reference to the
accompanying drawings, wherein:
25
cation Ser. No. 550,566 ?led August 22, 1944, by
G. H. Brown and D. W. Peterson and entitled
Radio power division networks. Such networks
operate e?iciently throughout an extremely wide
Figure l is a schematic plan view of an antenna
system constructed in accordance with the in
vention,
band of frequencies.
Figure 2 illustrates schematically the construc
tion of a preferred type of radiator element for
use in the system of Figure 1,
Figure 3 is a sectional view of a re?ector in
cluded in the system of Figure 1,
30
In order to secure the degree of horizontal di
rectivity required in certain applications, it is
necessary that each of the radiator groups I, 3,
5 and ‘I comprise three spaced radiators, excited
in phase. In the system of Figure 1, each of the
Figure 4 is a longitudinal section of a combined 35 radiator groups comprises three dipoles ll, 13
line balance convertor and power division device
and I5 disposed in end-to-end relationship and
employed in the system of Figure 1,
spaced‘at equal intervals. .To provide the re
Figure 5 is a cross section of the device of Fig
quired cophasal relationships, the dipoles of each
ure 4 along the line V-—V,
group are connected in parallel with each other
Figure 6 is a graph illustrating the standing 40 by means of transmission lines [6 extending to
junction points I’! and IS. The lines l6 prefer
wave ratio as a function of frequency on a feed
ably comprise coaxial cables. Two cables are re
line connected to the system of Figure 1, and
quired for each dipole; one for each radiator
Figure 7 is a graph illustrating the horizontal
element. The inner conductors only of the lines
beam width provided by the system of Figure l,
as a function of frequency.
,
The invention will be described as embodied
in a'system of the type illustrated in Figure 1,
which includes a generally conventional arrange
ment of four radiator groups I , 3, 5 and 1 dis
posed in a line substantially perpendicular to the
axis of the desired directive pattern. YVertical
directivity is provided by means of a re?ector 9
‘of conductive material in the form of a cylin
-
at equal intervals along the focal line of the
re?ector 9. The directive pattern of such an
array (i. e. four radiators, equally spaced, in line)
can be predicted in accordance with known en
‘ system of the type including a plurality of spaced
side lobes.
2
along the line of the centers of the radiators l,
3, 5, and 1. See Figure 3.
The radiator groups I, 3, 5 and 7 are spaced
45 it are shown in Figure 1. The outer conductors
are all connected together and grounded. To
provide excitation of the dipoles, current must
?ow into one of the radiator elements while cur
rent is ?owing out of the other element. Thus
50 each pair of the lines I6 functions as one con
ductor of a parallel conductor transmission line,
and the points ll and I9 must be of opposite
polarity.
‘
The junction points l1 and H! are the output
drical paraboloid with its focal line disposed, 55 terminals of a line balance convertor 2|, illus
aiidaé'i
trated in detail in Figure 4. The convertor 2i
has an unsymmetrical input circuit (that is, one
side is grounded) connected to a coaxial line 23.
The convertor 2! couples the unsymmetrical cir
cult of the line 23 to the symmetrical circuits of
the lines l6.
‘
Refer to Figure 4. The convertor 2i comprises
4
pair of cylindrical members 25, disposed in end
to-end relationship and each provided with a
plurality of transverse radial ?ns 21. The dimen
sions and spacings of the ?ns may be adjusted
to provide the required impedance characteristics.
The input ends of the lines 23 are connected
to a power dividing network 29 which may be of
the type described in the above-mentioned Brown
a conductive ‘sleeve l25 surrounding the ?nal
and Peterson application Ser. No. 550,566. The
quarter wave section of the line 23 and connected
device 29 includes a coaxial line section 3! one
l0
to the outer conductor thereof by means of a
half wavelength long at the center of the band
disc member I21. The sleeve 125 is one-half
of operation, connected at one end to a line bal
wavelength long at the center of the band of
ance converter 33 and at the other end to the
frequencies throughout which the system is to
main feed line 35 and to a quarter wave short—
operate. The outer end of the sleeve 125 is con~
nected by means of a disc 129 to a coaxial tubu 15 vcircuited stub 31. The convertor 33 comprises a
quarter~wave sleeve 39 surrounding the ?nal
lar conductor i3i, approximately one-quarter
quarter-wave-section of one of the lines 23 and
wavelength long and of a diameter substantially
connected thereto by a disc 4H. Another of the
equal to that of the outer conductor of the line
lines 23 has its outer conductor connected at the
23. The inner end of ‘the member IN is con
point 43 to- the sleeve 39 and its inner conductor
20
nected to the end of the inner conductor of the
connected ‘to the ?rst of the lines 23-. The two
line 23. The inner end of the conductor i3! is
the junction point IT, and the end of the outer
lines 23 thus far mentioned are connected re
conductor of the line 23 is the junction point is.
The outer conductors of the lines It are connected
are thus connected in series with each other
spectively to the radiator groups I and 7, which
through the convertor 33. 'Since current is ?ow
to the sleeve [25.
-'
ing into one of these lines while current is ?owing
In operation, the member l3l cooperates with
out of the other, the connections to the dipoles
the sleeve I25 to function as a quarter wave line
of the‘group ‘i must be reversed with respect to
‘short-circuited at one end. Similarly, the outer
those of the group I in order that groups 5 and ‘I
conductor of the line 23 cooperates with the
shall operate in ‘phase. ‘The remaining pair of
sleeve 125 to function as a second quarter wave 30 lines 23 extending to the radiator groups 3 and 5
line short-circuit'ed at the other end. Current
are connected in parallel to each other to the line
flowing in on the inner conductor of the line 23
?ows down the ‘member 'l-3l to the disc I29, thence
through the sleeve I25 to the outer conductor
of the line 23, and along the outer surface of
the outer conductor of the line 23 in the same
direction as the current on the conductor 13L
Thus the junction points ll and I9 are sym
metrical with respect to ground; and current is
3!. The characteristic impedance of the section
3! is determined in accordance with the im
pedances of the lines 23 as described in detail
in said Brown and Peterson application, for co
operation with the stub 31 to provide substantial
compensation of the re'actance of the converter
33.
Since the lines extending to the radiator
groups 3 and 5 are in parallel to each other across
‘?owing into one while current flows out of the 40
other, ful?lling the requirement for symmetrical
the input circuit, and those extending to. the
excitation of the dipoles connected to the
theinput circuit, '10 percent of the input power
lines l6. '
It should be noted that the coupling of the line
it to the line 23 is substantially ‘equivalent to
a series parallel connection. That‘is, if each of
the‘ lines It has a characteristic impedance of
75 ohms, and is matched at its load end, the im
pedance presented to the line 23 is
2X75
————,3 ‘
or 50 ohms.
In an antenna system of the de
scribed type it is highly desirable to employ co
axial lines of standard commercially obtainable >
characteristics. 50 ohms and 75 ohms are both
standard impedances. '75 ohm cables may be
used for lines Iaand 50 *ohm'cables for the
lines 23.
.
>
The conventional dipole structure exhibits a
relatively low impedance, particularly if designed
in accordance with conventional practice to pro
vide broad band operation. However, structures >
of the type illustrated in Figure 2 and described: ‘
and claimed in copending U. S. application Ser.
No. 552,095, ?led August 31, 1944, by D. W. Peter
son and entitled Broad band radiator, may be
designed to provide an impedance which remains
relatively constant at a value of'the order of '70
ohms over a broad band of frequencies. vIf such
elements are used in the dipoles H, i3 and t5,
groups 1 and “l are in series with each other across
will ?ow to each of the groups I and ‘l and iii)
percent will flow to each of ‘the ‘groups 3 and 5.
The impedance looking ‘into the line 35 is ap
proximately 20 ohms. This may be matched to
a 50 ohm line by means of a coaxial transformer
comprising a series of quarter-wave line sections
of consecutively increasing characteristic im
pedances. This type of transformer, which is
described and. claimed in U. S. Patent 2,249.59'1‘,
will operate over a wide band of frequencies with
out variations in performance such as result from
the use of matching stubs.
The graph of Figure 6 illustrates the variation
with frequency of the standing wave ratio ap
pearing on the input line "35. ‘This gives an indi
cation of the variations of impedance of the sys
tein 'with‘frequency. The curve of Figure '7 is
the result of measurements made upon asystem
like that ‘shown in Figure 1, designed for opera
tion over the frequency band of approximately
400 to 900 megacycles per second.
'
The graph of Figure 7 illustrates the variation
with frequency of the horizontal width at half
held ‘of the beam provided by the system of Fig
ure 1.
The beam becomes narrower as the fre
quency is increased, ‘owing to the fact that the
various dimensions 'of ‘the system become increas
ingly larger in relation to ‘the wavelength.
Briefly summarizing the above description, the
invention
comprises an'improved broad band di
throughout theoperating range.
‘
rective antenna system wherein high impedance
Referring to Figure 2, a typical ‘dipole ‘struc
ture of the above-mentioned type comprises a 5 dipoles are employed to enable the use of coaxial
the lines It will remain substantially matched
2,410,597
5
transmission lines of standard impedances, and a
power division network of the line balance con
vertor type is used to enable accurate power di
vision and e?cient power transfer throughout a
wide band of frequencies. Power is subdivided
between the radiator elements of each radiator
group by means of a combined balance converter
the corresponding transmission line so as to coue
ple all of the dipoles of each group in parallel
with each other to the respective line, a main
feed line, means for coupling said coaxial; lines
associated with the outer pair of said groups in
series with each other to said main feed line,
and means for coupling said coaxial lines, asso
ciated with the inner pair of said groups in par
allel with each other to said main feed line.
10
5. A broad band directive antenna system, in
cluding a re?ector in the form of a cylindrical
described as embodied in an antenna including
paraboloid, four groups of radiator elements dis
four radiator groups, it will be apparent to those
posed in line along the focal line of said re?ector,
skilled in the art that the principles disclosed
and power division device which also operates
with high efficiency throughout the required fre
quency band. Although the invention has been
each of said groups comprising a plurality of
collinear dipoles, four transmission lines extend
ing respectively to said radiator groups, means
for coupling all of the dipoles of each group in
are used as subcombinations.
parallel with each other to the respective line, a
The invention covered herein may be manufac
main feed line, means for coupling said linesv as
tured and used by or for the Government of the
United States for any governmental purpose 20 sociated with the outer pair of said groups inse
ries with each other to said main feed line, and
without payment to me or assigns of any royalty
means for couplingsaid lines associated with, the
thereon.
inner pair of said groups in parallel vwith each
We claim as our invention:
other to said main feed line.
> > '
1. A broad band directive antenna system, in
6. A broad band directive antenna system, in
cluding four groups of collinearly disposed radi
cluding a re?ector in the form of a cylindrical
ator elements, constituting two side groups and
paraboloid, four groups of radiator elements dis
two center groups, four coaxial transmission
posed in line along the focal line of saidre?ector,
lines, one coupled to each of said groups respec
each of said groups comprising a plurality of col
tively, a main feed line, means for coupling said
linear dipoles, each dipole comprising a pair of
coaxial lines associated with said side groups in
tubular conductors provided with a plurality of
series with each other across said main feed line,
conductive fins lying in planes at right angles to
and means for coupling said coaxial lines asso
the axis of said conductors, four coaxial transmis
ciated with said center groups in parallel with
sion lines extending respectively to said radiator
each other across said main feed line.
2. A broad band directive antenna system, in 35 groups, line balance converter means connected
to each group and to the corresponding trans
cluding four groups of radiator elements consti
mission line so as to couple all of the dipoles of
tuting two side groups and two center groups,
herein may be applied with similar advantage to
antennas comprising larger numbers of radiator
groups, in which structures like that of Figure 1
each group in parallel with each other to the re
spective line, a main feed line, means for coupling
tending respectively to said radiator groups, line 40 said coaxial lines associated with the outer pair
of said groups in series with each other to said
balance convertor means connected to the dipoles
of each group and to the respective transmission
main feed line, and means for coupling said co
axial lines associated with the inner pair of said
line so as to couple all of the dipoles of each group
groups in parallel with each other to said main
in parallel with each other to the respective line,
feed line.
a main feed line, means for coupling said coaxial
'7. A broad band directive antenna system, in
lines associated with said side groups in series
cluding a re?ector in the form of a cylindrical
with each other to said main feed line, and
paraboloid, four groups of radiator elements dis
means for coupling said coaxial lines associated
posed in line along the focal line of said re?ector,
with said center groups in parallel with each
each of said groups comprising three dipoles, each
other to said main feed line.
dipole comprising a pair of tubular conductors
3. A broad band directive antenna system, in
provided with a plurality of conductive ?ns lying
cluding a re?ector in the form of a cylindrical
in planes at right angles to the axis of said con~
paraboloid, four groups of radiator elements dis
ductors, four coaxial transmission lines extend
posed in line along the focal line of said re?ector,
ing respectively to said radiator groups, line bal
each of said groups comprising a plurality of col- ance convertor means connected to each group
linear dipoles, four coaxial transmission lines ex
and to the corresponding transmission line so as
tending respectively to said radiator groups, line
to couple all of the dipoles of each group in par
balance converter means connected to each group
allel with each other to the respective line, a main
and to the corresponding transmission line so as
to couple all of the dipoles of each group in par 60 feed line, means for coupling said coaxial lines
associated with the outer pair of said groups in
allel with each other to the respective line, a
series with each other to said main feed line, and
main feed line, means for coupling said coaxial
means for coupling said coaxial lines associated
lines associated with the outer pair of said groups
with the inner pair of said groups in parallel with
in series with each other to said main feed line,
and means for coupling said coaxial lines associ 65 each other to said main feed line.
8. A broad band directive antenna system, in
ated with the inner pair of said groups in paral—
cluding a re?ector in the form of a cylindrical
lel with each other to said main feed line.
paraboloid, four groups of radiator elements dis
4. A broad band directive antenna system, in
posed in line along the focal line of said reflec
cluding a re?ector in the form of a cylindrical
paraboloid, four groups of radiator elements dis 70 tor, each of said groups comprising a plurality
of collinear dipoles, each dipole comprising a pair
posed in line along the focal line of said reflector,
of tubular conductors provided with a plurality
each of said groups comprising three collinear
of conductive ?ns lying in planes at right angles
dipoles, four coaxial transmission lines extending
to the axis of said conductors, four transmission
respectively to said radiator groups, line balance
convertor means connected to each group and to 75 lines extending respectively to said radiator
each of said groups comprising a plurality of col
linear dipoles, four coaxial transmission lines ex
7
8
groups, means for coupling all of the dipoles of
each- group in parallel with each other to the re‘
spective line, a main feed line, means for coupling
said lines associated with the outer pair of said
said radiator groups, a main feed line,v and line
balance converter means for coupling said lines
associated with certain pairs of said groups in se
ries with each other to said main feed line, and
groups in series with each other to said main feed
line, and means for coupling‘ said lines associated
for coupling said lines associated with the re
mainder of said groups in parallel with each other
to said main feed line.
with the inner pair of said groups in parallel with 4
each other to said main feed line.
'
11. A broad band directive antenna, including
9. A broad band directive antenna system, in
a plurality of spaced groups of radiator elements
cluding a re?ector, four groups of radiator ele 10 disposed in pairs symmetrically about a central
ments disposed in cooperative relationship with
line, each of said groups comprising a plurality
said re?ector, each of said groups comprising a
of collinear dipoles, each dipole comprising a- pair
plurality of dipoles, four coaxial transmission
of tubular conductors provided with a plurality of
lines extending respectively to said radiator
conductive fins lying in planes at right angles to
groups, line balance convertor means connected 15 the axis of said conductors, transmission lines ex
to each group and to the corresponding transmis
tending respectively to said radiator groups, line
sion line so as to couple all of the dipoles of each
group in parallel with each other to the respective
line, a‘ main feed linemeans for coupling said
balance converter means connected to each group
and to the corresponding transmission line so as
to couple all of the dipoles of each group in par
coaxial lines associated with one pair of said 20 allel with each other to the respective line, a
groups in series with each other to said main feed
main feed line, and line balance converter means
line, and means for coupling said coaxial lines
for coupling said lines associated with certain
associated with the other pair of said groups in
pairs of said groups in series with each other to
parallel with each other to said main feed line.
said main feed line, and for coupling said lines
‘10. A broad band directive antenna; including
associated with the remainder of said groups in
a plurality of spaced groups of radiator elements
parallel with each other to said main feed line.
disposed in pairs symmetrically about a central
'
GEORGE H. BROWN.
line, transmission lines extending respectively to
DONALD W. PETERSON.
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