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Jan- 7, 1947.
27,413,951
P. s. CARTER
ANTENNA SYSTEM
Filed June 3,‘ 1942
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Jan- 7, 1947.
P. s. CARTER
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2,413,951‘
ANTENNA SYSTEM’
Filed June '3, 1942
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BY
AfroRNEY .
2,413,951
Patented Jan. 7, 1947
UNITED STATES ‘PATENT OFFICE
2,413,951
ANTENNA SYSTEM
Philip S. Carter, Rocky Point, N. Y., assignor to
Radio Corporation of America, a corporation of
Delaware
Application June 3, 1942, Serial No. 445,560
22 Claims. (Cl. 250—11)
1
The present invention relates to short wave
antennas and, more particularly, to directive an
reference to the following detailed description,
which is accompanied by drawings in which Fig
tenna systems for use on airplanes.
ure 1 illustrates in simpli?ed perspective an ar
An object of the present invention is the pro
rangement of the present invention; Figure 2
vision of a directive antenna array having a
is a schematic diagram explanatory of the prin
radiation pattern free from secondary lobes or
ciples of the present invention, while Figure 3
illustrates the resultant directivity pattern in the
ears.
horizontal and vertical planes for an antenna
Another object of the present invention is the
array as shown in Figure 1; Figure 4 is a curve
provision of a high gain directive antenna array.
Still another object is the provision of a multi 10 illustrating the relationship between the spacing
of the elements of the array of Figure 1 and the
unit antenna in which current distribution in
power gain, while Figure 5 illustrates a proposed
each of the radiator units is substantially un
arrangement of the antenna array of Figure 1
affected by the other units.
with respect to a conductive sheet representing
A further object of the present invention is the
association of radiators and a transmission line in 15 the body of an airplane and Figure 6 is a direc
tivity pattern of the array of Figure 5, Figure '7
such manner that the current in each of the
illustrates the arrangement of the antenna of
radiators is substantially independent of the im
Figure 1 with respect to a conductive sheet repre
pedance of the radiators.
senting an airplane wing, while Figure 8 is'a
7 Still a further object of the present invention
is the provision of a multi-unit antenna in which 20 directivity pattern illustrating the effect of the
wing on the radiator. _
the ratio between the currents in the radiator
In Figure 1 I have shown a two tier antenna
elements is controlled substantially only by the
characteristic impedance of the transmission line
sections connecting the elements.
array. One tier, identi?ed by reference numeral
It, consists of three half wave dipoles II, I2
apart one quarter of the operating wavelength
along a transmission line, the end dipoles being
the phase opposing current relationship: between
Another object of the present invention is the 25 and I3 side by side with a quarter wave spacing
between them. A second similar tier I0’, spaced
disposition of an antenna array with respect to
from the ?rst tier a distance S, includes three
the body and wing structure of an airplane so as
half wave dipoles Il', I2’ and I3’. The dipoles
to obtain a desired directivity pattern.
of tier It are connected to a transmission line I5.
_ The foregoing objects, and others which may
The transmission line I5 is transposed near its
appear, from the following detailed description,
point of connection to dipole I3 so that the cur
are attained in‘ accordance with the principles
rents in the end radiators are in phase opposi
of the present invention by providing an antenna
tion. Of course, any other means for obtaining
array of three coplanar dipole radiators spaced
the end dipoles may be used. The current in the
center unit I2 is arranged to be twice that of
the outer units in magnitude and in phase
so connected to the transmission line that they
are energized in phase opposition. The trans
mission line is energized at the location‘oi the
center dipole. The impedance of the transmission
line is so adjusted that the current in the center
dipole is twice that in the end dipoles thus ob
taining a unidirectional directivity pattern. The
antenna arrangement may include a plurality
of arrays as set forth above arranged inparallel
planes and energized in phase. The spacing be 45
tween the arrays is so arranged as to obtain an
optimum power ratio or power gain with respect
to a single half wave dipole taken as a standard.
By an appropriate arrangement of such an array
with respect to the body and ring structures of
an airplane a resultant directivity is obtained
having a maximum response in a predetermined
direction with respect to the longitudinal axis of
the plane.
quadrature with each of the latter. The proper
amplitude relationships are determined substan—
tially only by the impedance of the various sec
tions of the connecting transmission line I5. In
some circumstances it may be desirable to inter
pose matching circuits between dipole I3 and the
transmission line for adjusting the relative values
of currents in dipole l2 with respect to dipoles
II and [3. It should be noted that the field set
up along dipole l2 by the current in dipole II
is exactly out of phase with that set up by the
current in dipole I3. This, of course, is equivalent
50 to a zero value of mutual impedance between
the center dipole I2 and‘th'e pair of dipoles II
and I3. The connection of transmission line
IE’ to. dipole units I I’, I2’ and I3’ is similarly ar
ranged. The two tiers Ill and ID’ are energized
. The invention will be more fully understood by 55 from a suitable source of high frequency energy
2,413,951
‘
4
3
(not shown) connected to transmission line TL.
and leads the latter currents by 90°. The imped
The manner in which a uni-directional direc
ances of dipoles II and I3 may be different from
each other and di?erellt from the impedance of
IE without affecting their currents either in am
tivity pattern is obtained from each of the tiers
of Figure 1 will be more clearly understood by
reference to Figure 2.
‘
plitude or phase.
Here, an equivalent antenna array is shown in
a side view. Dipole antennas II and I3 are as
before described while the center dipole has been
replaced by a pair of equivalent dipoles 22 and
22'.
Now, if only dipoles II and 22' are con
For this reason this antenna
is relatively insensitive to detuning effects caused
by the presence of water, ice, etc., on the dipole
elements themselves.
The directivity in the vertical plane, of an an
10 tenna constructed in accordance with Figure l.
sidered to be energized in phase quadrature with
is shown in Figure 3, curve 3i being the measured
currents of equal amplitudes a directivepattern
substantially cardioid in shape with the maxi
pattern actually determined by experimentation
mum of the cardioid in the direction of arrow M
tern.
and test, and curve 32 being the calculated pat
It will readily be seen that the measured
is obtained. Similarly, if only dipoles I3 and 22 15 and theoretical values agree very closely and in
are considered another cardioid having its maxi
either case are quite free from secondary lobes or
mum in the same direction is obtained. Now, if
cars. Curve 33 of Figure 3 shows the directivity
the center arrangement of dipoles 22 and 22’
in the horizontal plane, that is, the plane parallel
is replaced by a single dipole carrying a current
to the plane in which tiers It! and I0’ lie. This
equal to the sum of the currents of dipoles 22 20 pattern is also characterized by the substantial
absence of secondary lobes or ears.
and 22' the two separate cardioids combine in
an additive relationship to obtain a resultant
The curve in Figure 4 illustrates the effect of a
maximum along arrow M. It will be apparent
variation in the spacing S between the planes in
from the following analysis that the use of a
which tiers I0 and I0’ lie. When the tier space
quarter wavelength transmission line between the 25 S is a half wavelength the gain over that obtained
point of connection of transmission line TL to
with a half wave dipole is a little over 5 with the
gain increasing somewhat with increasing spac
dipole I2 and each of the dipoles II and I3 re
ing up to a value of about .78 wavelength spacing.
sults in the currents in dipoles II and I3 being
substantially independent of the impedance of
The body and wings of an airplane, with which
antennas II and I3 and depending only upon
the antenna of the present invention is associated,
the value of the characteristic impedance of the
have a considerable effect on the radiation pat
line TL.
tern of the antenna. When the antenna is
mounted as shown in Figure 5, at a distance of
If one considers transmission line TL as sup
the order of 0.4 wavelength from a conductive
plying a voltage E1. and the current of Ir. to a
section of transmission line, such as one-half of 35 sheet 50 simulating the side of the body of the
airplane and a distance D from the front edge of
transmission line 95, the section having a char
the sheet, a radiation pattern such as that shown
acteristic impedance Z0 and length 1, the voltage
in Figure 6 is obtained. It will be noted that the
Em and current In at the remote end thereof are
directivity pattern is somewhat sharper as the
given by the following equations:
40 distance D increases, curve 5| of Figure 6 show
ing the case wherein a distance D of the order of
21A; wavelengths is used and curve 52 where a
distance D equal to 1.3 wavelengths is used.
Figure 7 shows the disposition of a single tier
of the antenna structure of the present invention
From these two equations it will be noted that
at a distance equal to a half wavelength from a
if the length I of the line sections is an odd mul
conductive sheet 10 simulating the lower surface
tiple including unity of a quarter wave the ?rst
of the wing of an airplane, while Figure 8 shows
expression to the right of the equality sign in
the effect of a variation in distance X, between
each of the equations drops out. The current at 50 the center of the antenna tier and the center of
each end of line I5, i. e., the current in dipoles
curvature of the front edge of the wing. Curve
H and I3, is therefore equal in magnitude to the
‘II shows the directivity pattern for a distance X
ratio of the voltage E1. on line I5 at dipole I2
equal to one wavelength, while curve 12 indicates
to the characteristic impedance Z0 and lags the
the directivity for a distance X equal to 0.2 wave
voltage Er. by 90° in phase as indicated by the 55 length.
factor (-7'). The value of the impedance of the
For the particular application for which the
dipoles I I and I3 does not enter the relationship
antenna of the present invention was designed,
in any way so long as the length of the line I5
the directivity shown by curve 5| of Figure 6, and
is an odd multiple including unity of a quarter
curve ‘I2 of Figure 8 very closely approximate the
wave length from feed point to load.
60 ideal. For example, it is required that a maxi
The current in dipole I2, which is in effect
mum in the horizontal plane occur at about 18
directly connected across transmission line TL
degrees with a minimum somewhere in the vicin
is equal to the ratio of the voltage E1. to its im
ity of 40 degrees. The spacing of 0.4 wavelength
pedance Z12 which is approximately 71 ohms re
between the center of the antenna and the body
sistive when tuned. By giving the characteristic 65 of the plane ful?lls these requirements quite
impedance of the line a value of 142 ohms the
closely, while doubling the spacing almost exactly
currents I11, I12 and I13 in dipoles I I, I2 and I3
reverses the conditions, that is, there is a‘ mini
respectively are given by the relations:
mum at 20 degrees and a maximum at'about 40
and I12/Z11=I1z/I1s=+7'2, showing that the cur
rent in the center dipole I2 has a magnitude of
twice that for the current in the outer dipoles
degrees. It is also desired that the antenna be‘
70 most efficient at or near the horizon and this con
dition occurs with the antenna placed at about
0.2 wavelength back of the front edge of the wing.
It will be noted that, particularly with respect
75
to the directivity pattern in the vertical-plane, the
results obtained appear to con?ict with assump
2,418,961
5
itions heretofore :commonly made as :to the effect
or aconducting sheet in ‘the ?eld .of the ‘antenna.
It has sometimes ‘been assumed ‘that where :the
radius of the conducting sheet from ‘the center
of the antenna is ‘of ‘the ‘order .of three :wave
‘lengths, the sheet maybe considered as an in
?nite plane. ‘The .pattern actually obtained
shows, however, “that three wavelengths is ‘not
6
‘for coupling ,rhigh .ifrequency transducer means ‘to
‘the ‘center :radiator elements and transmission
line sections ,coupling'ieach of said end elements
to said transducermeansthe characteristic im
pedance ,of¢each.of said‘sections being twice the
radiation resistance :of, said center element.
521A directive antenna system including three
radiator‘lelements arranged along a desired line
even an approximation of an in?nite plane.
cifldiitectivity, said elements being spaced apart
There is over e30 degree ‘variation .between‘the 10 ‘a distance vequal to a quarter wavelength, means
maximum values obtained with a. sheet of v3 wave
for ‘coupling high frequency transducer means
lengths radius ‘and those which wouldbe expected
to the center radiator elements and quarter wave
if the sheet were actually in?nite. ‘If the sheet,
transmission line section's coupling each of said
actually acted asianin?nite-‘plane-fthe maximum
end elements to said transducer means, the char
directivity would, .of ‘course, the parallel ‘to ‘the 15 acteristic impedance of each of said sections be
‘planeof the sheet.
ing twice the vradiation resistance of said center
While I ‘ have ‘particularly, shown and described
‘element.
several‘modi?cations ,of my invention, it is to be
8. A directive antenna system including three
distinctly understood that my invention is :not
radiator elements arranged along ‘a desired line
limited thereto ‘but that improvements within the 20 of directivity, said elements being spaced apart
scope of the invention may be made.
distance equal to a quarter wavelength, means
Iclaim:
for coupling “high frequency transducer means
l. A directive antenna‘system‘including three
to the center radiator elements and quarter wave
radiator elements arranged alongadesired line
transmission line sections coupling each of‘said
of directivity, a transmission line carrying high
end elements to said transducer scans, the char
frequency currents coupled to said'radiator ele
acteristic impedance ‘of each of said sections be
ments, the characteristic impedance of the ‘per
mg "twice the radiation resistance of said center
tions or said transmission line between ‘each end
element {and the center element being twice ‘the
radiation resistance of saidcenter element.
' .2; A .directivexantenna system including three
radiator elements .arranged- along a desired
line of directivity, said elements being spaced
apart a distance equal to a quarter wave
length, a transmission ‘line carrying high fre
quency currents coupled to said ‘radiator ‘ele
ments, thecharacteristic impedance of ' he per;
tions of said'transmission line between each .end
element and the center element being twice the
radiation resistance of said ‘center element.
directive antenna. system including ‘three
radiator elements arrangedalong a desired line
of directivity, a transmission line carrying 'high
element, zone of said end elements being ener
glued in phase opposition to the other.
An antenna system including a plurality of
radiator elements and a source of high frequency
energy coupled ‘thereto characterized in that the
‘cur-rent ‘in one of ‘said elements is equal to the
sum of the currents in the remainder, said re
mainder being coupled ‘to said one element
through "transmission line sections, each having
a’length equal to a quarter wavelength and hav
ing a characteristic impedance equal to'N times
‘the radiation resistance ‘of said one element
where N is the number of remaining radiator
elements.
~
'
10. A. radiant energy system including three
radiator elements, two of said elements being
" ‘equeucy currents ‘coupled to said radiator ele
ts, the characteristic impedance of the por 45 coupled ‘to transducer means by quarter wave
‘transmission line sections and the third directly
tions of said transmission line between each end
coupled thereto, the characteristic impedance of
element and the “center element being twice the
each of ‘said sections ‘being twice the radiation
radiation resistance of said center *element'said
resistance of said third radiator element.
transmission line being energized at the point
11. A radiant energy system including three
of coupling of the center radiator element.
radiator elements, two of said elements being
4.. A directive-antenna ‘system including three
coupled to transducer means by quarter Wave
radiator elements arranged along a desired line
transmission ‘line sections and. the third directly
of directivity, said elements being spaced apart
coupled thereto, the characteristic impedance of
distance equal to a quarter wavelength, a trans
each of said sections being twice the radiation
mission line carrying high ‘frequency currents
resistance of said third radiator element, one of
coupled to said radiator elements, the character-é
said two elements being coupled to said means
istic impedance of the portions of said transmis- ‘
in an opposite phase'relationship to the other.
sion line between each end element and ‘the cen
12. An antenna system including a plurality
ter element being twice the radiation resistance
of‘tiers of directive antenna structures, each tier
of said center ‘element, said transmission line be
being constituted in accordance with claim 7,
ing energized at the point of coupling of the cen-_
ter radiator element.
said tiers being arranged in parallel planes.
13. An antenna system including a plurality of
tiers of directive antenna structures, each tier
being constituted in accordance with claim '7,
transducer means to the center radiator elements 05 said tiers being arranged in parallel planes, the
spacing between said planes being of the order of
and quarter wave transmission line sections cou-
5. A directive antenna system including three
radiator elements arranged along a desired line
of directivity, means for coupling high frequency
.‘7 of a wavelength.
pling each of said end elements to said trans
14. An antenna system including a plurality
ducer means, the characteristic impedance of
, of tiers of directive antenna structures, each tier
each of said sections being twice the radiation
being constituted in accordance with claim 7,
resistance ‘of said center element.
said tiers being arranged in parallel planes and
6. A directive antenna system including three ;energized in a similar phase relationship.
radiator elements arranged along a desired line
15. An antenna system including a plurality of
of directivity, said elements being spaced apart
‘tiers of directive antenna structures, each tier
a distance equal to a quarter wavelength, means 75 being constituted in accordance with claim 5, said
2,413,951
26; A directive antenna structure comprising
three radiator elements arranged along a straight
line and each spaced from its adjacent one by an
odd multiple including unity of a quarter wave
in a similar phase relationship.
length at the operating frequency, two-conductor
16. An antenna system including three co
transmission line sections connecting the center
planar radiator elements arranged perpendicular
radiator element to the other two radiator ele
to a common axis, said elements being spaced
ments, said line sections having such impedances
along said axis a distance equal to one-quarter
that the current in the center radiator element
of the operating wavelength, the end elements of
said antenna being energized in phase opposition ' ’ is substantially twice the current in either of
the other two ‘radiator elements, one of said line
and the center element in a quarter phase re
sections having its conductors transposed, a simi
lationship with respect to each of said end ele
lar directive antenna structure arranged parallel
ments, the plane of said antenna being arranged
to said ?rst antenna structure and spaced there
normal to a conductive sheet and at such dis
from in such manner that corresponding radiator
tance therefrom, and said sheet extending in a
elements and transmission line sections are simi
direction parallel to the longitudinal axis of said
larly positioned, a transmission line section join
antenna at such distance that the line of maxi,
ing the two center radiator elements of both
mum directivity of said antenna forms an angle
structures, and a feeder line connected to said
of the order of 20 degrees with said axis.
17. A directive antenna structure including 20 lastline section at a location substantially mid
way relative to bothcenter radiator elements.
three radiator elements arranged along a de
21. A directive antenna system comprising
sired line of directivity, said elements being spaced
three
dipole radiator elements having their cen
apart a distance equal to one-quarter of the
ters arranged along a straight line and each
operating wavelength, the end elements of said
spaced from the adjacent one by a distance sub
system being energized in phase opposition and
stantially equal to an odd multiple including
the center element in a quarter phase relation
unity
of one quarter wavelength at the operat
ship with respect to each of said end elements,
ing frequency, said dipole elements being parallel
another similar directive antenna structure ar
to each other and arranged substantially at right
ranged parallel to said ?rst structure and spaced
tiers being arranged in parallel planes, the spac
ing between said planes being of the; order of .7
of a wavelength and said tiers being energized
therefrom by a distance of the order of .7 wave
length at the operating frequency.
18. A directive antenna structure including
three radiator elements arranged along a desired
line of directivity, said elements being spaced
apart a distance equal to one-quarter of the op
erating wavelength, the end elements of said
system being energized in phase opposition and
3 (l
angles to said straight line, a feeder line con
nected directly to the center radiator element,
two-conductor transmission line sections con
meeting said center radiator element to the other
two radiator elements, said line sections having
‘such impedances that the current in the center
radiator element is substantially twice the cur
rent in either of the other two radiator elements,
one of said linesections having its conductors
transposed whereby the currents in the outer
ship with respect to each of said end elements,
radiator elements are in phase opposition to each
another similar directive antenna structure ar 40 other and in a quarter phase relation with respect
ranged parallel to said ?rst structure and ener
to the center radiator element.
gized in a similar phase relationship.
22. An antenna system including three co
19. A directive antenna system comprising
planar radiator elements spaced from one an
three radiator elements arranged along a straight
other by a distance equal to an odd multiple in
line and each spaced from the adjacent one by a
cluding unity of a quarter wavelength and ar
distance substantially equal to an odd multiple
ranged in a straight line, a_ two-conductor feeder
including unity of one quarter wavelength at the
energizing the center one of said elements, trans
operating frequency, a feeder line connected di
mission line sections connecting the center radi
rectly to the center radiator element, two-con
ator element to the other two radiator elements,
ductor transmission line sections connecting said 51) one
of said transmission line sections having its
center radiator element to the other two radiator
conductors
transposed, the lengths of each of
elements, said line sections having such imped
said
transmission
line sections being an odd mul
ances that the current in the center radiator ele
tiple including unity of a quarter wavelength
ment is substantially twice the current in either
from the feed point to the element being fed, said
of the other two radiator elements, one of said
line sections having such impedances that the
line sections having its conductors transposed
current
in the center radiator element is substan
whereby the currents in the outer radiator ele
tially twice the current in either of the other two
ments are in phase opposition to each other and
radiator elements.
in a quarter phase relation with respect to the
PHILIP S. CARTER.
center radiator element.
the center element in a quarter phase relation
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