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NOV» l2, 1946
T. M. GLuYAs, JR., ET AL
Filed Feb. 24, 1943
(Ittorneg '
Patented Nov. 12, 1946
Thomas M. Gluyas, Jr.,`CollingsWood, and Lester
J. Wolf, Audubon, N. J., assignors to Radio Cor
poration of America, a corporation of Delaware
Application February 24, 1943, Serial No. 476,888
5 Claims. ( Cl. 250-11 )
This invention relates to directive antennas
and more particularly to an antenna system for
matic diagram of an antenna array and its as
providing alternately overlapping directive lobes.
sociated circuits arranged according to the pres
In some applications it is desirable to radiate or
pick up energy alternately in two relatively nar
ent invention, Fig. la is a side view of a radiating
element mounted in front of a screen, Figs. 2
row overlapping lobes.
This may be accom
plished by an array of spaced dipoles energized
or coupled together in such phase relationships
that the resultant directive pattern comprises a
beam whose axis may be shifted by suitable vari
ation of the phase relationships between the sev
eral elements. In such applications as require
two discrete lobes, without any intermediate di
rectivity, the changes in phasing may be provided
by a switching mechanism of some sort. The
arrays used for this purpose generally comprise
at least one central group of radiating elements,
- and one or more groups of side elements disposed
symmetrically with respect to said central group
and phased in opposite senses with respect to said
accompanying drawing, of which Fig. 1 is a sche
and 2A are schematic diagrams of antenna ar
rays explanatory of the operation of the system
of Fig. 1, Fig. 3 is a group of curves representing
the components of a radiation ñeld produced by
the eiïect of the -in-phase currents in the system
cf Fig. 1, and Fig. 4 is a group of curves illustrat
ing the production vof the directive iield by all
of the currents in the system of Fig. 1.
Referring to Fig. 1,-the antenna array to be
¿ described comprises a central group I of radi
ator elements and two side groups 3 and 5,
symmetrically located with respect to the central
A concentric line 'l is connected to a
ractive effect on the other side. The problem
of switching radio frequency energy, particu
larly when relatively large peak power is in
radio device, not shown,l which 'may be a re
ceiver, a'transmitter, or both. The line 1 is con
nected directly by a concentric line 9 to the cen
tral >group I. .In'order to convert from the elec
trically unsymmetri'cal concentric line to a cir
cuit which is symmetrical with respect to the
ground, suitable for connection to dipole anten
volved, has been met to some extent by the em
na elements, a concentric line transformer II is
central group so as to provide an additive effect
on one side of the axis of the array and a sub
provided. This device comprises a relatively
large cylindrical conductive section 1A Wave
ing movable make-and-break contacts. Another
problem which arises in the design and opera
length long, connected at its base to the outer
tion of directive arrays of the above described 30 conductor of the line 9. The central group com
prises two parallel dipoles spaced apart IÁQ Wave
type is the elimination of undesired secondary
lobes in the radiation pattern. In order to
length and connected in parallel as shown. Each
or" the side groups comprises a similarly arranged
achieve the desired sharpness of directivity
While avoiding secondary lobes it is usually neces
pair of dipoles. The center line of each side
sary to use an array comprising a large number
group is 5A; wave length from that of the central
ployment of capacitor type switches, thus avoid
of elements, and on ship board and in other Ino
bile installations there is usually a definite limit
through concentric line transformers I3 and I5
and lines I'l and I9 respectively to the switching
circuit at the junction points 2I and 23. The
to the size of the array which can be tolerated.
It is the principal object of the present inven
tion to provide an improved method of and
means for providing alternately overlapping ra
diation directive patterns..
Another object is to provide a directive antenna
array for the above- purpose which is relatively
simpleand compact in construction.
A further" object is to provide an improved
method of and means for changing the ener
gization of the various elements of an antenna
Aarray for the purpose of controlling the directive
pattern thereof.
A further object is to provide an improved
capacitor type switch.
The side groups 3 and 5 are coupled
points 2I and 23 are connected together by a line
25 of a length‘equivalent to 50 electrical degrees.
The point 2I is connected through a, line 21, 1A;
wave length long, to a, junction point 29. The
point 29 is connected through a line 3l to a
stationary capacitor plate 33 and through a 1A;
wave line 35 to a junction point 37. The junc
tion point 23 is similarly connected through a
1A; wave line 39 and lines 4I and 43 to a stator
plate 4G' and to the junction 3l. YA stub line 45
60 is connected to thejunction point between the
lines 39, 4I and 43 and a similar stub Ill is con
nécted to the opposite junction point 29. The
These and other objects will become apparent
vcapacitor switch @9 includes the stator plates 33
to those skilled in the art upon consideration of
and Lida pair of stator plates 5I and 53, and a
the following description with reference to the 55 single rotor plate 55. The stator plates 5I and
53 are connected to stub lines 51 and 59 respec
tively. The rotor plate 55 is mechanically con
nected to a motor 6I provided with a suitable
power supply, not shown.
operation is the solid line curve 11, which rep
resents the resultant ñeld produced by the corn
plete array with one position of the switch 49.
When the switch lis is in its opposite position,
Referring to Fig. 2, the radiation from pairs of
the quadrature current component represented
radiators along a line symmetrically disposed
with respect to the midpoint of the line is of
by the curve "il is reversed, providing a resultant
similar in shape to the resultant 11 but inverted
with respect to the bearing axis. With the de
the form:
sign illustrated in Fig. 1 the ñeld pattern is 30°
10 wide at the half energy point and the lobe dis
placement is 6° from the center line. -It should
be noted that the curves 1l and 13 are approxi
Where K is a constant, I1, Iz . . . are the radiator
currents, of phase angles ai, «x2 . . ., and B1 B2
. . are the radiator spacings in radians.
For an add number of radiators (Fig. 2A) :
mately tangent at their point of nearest ap
proach, which occurs at an angle of about 45°.
15 If the currents and phases of the radiator ele
ments are so arranged that these curves do not
cross, no spurious radiation lobes are produced.
The rotating capacitor ¿l5 is part of a series
resonant circuit which alternately grounds the
The actual field pattern may be determined by
junction points 29 and lill. A short circuit at
multiplying the above expression by the direc 20 the
junction point 29 reflects an open circuit at
tivity pattern of the radiator element, including
junction points 2l and 31 as a result of well
the effect of the reflecting screen. This factor
lrnown impedance inversion characteristics of
may be determined experimentally with a single
quarter wave transmission lines. Similarly a
radiator element. In the array of Fig. l the
short circuit at the junction point ¿lll reilects open
dipole elements are supported 1/8 wave length in 25
circuits at points 23 and 31. The inductance
iront of a screen ‘53, as illustrated in Fig. 1A.
of the stub line ¿il together with the capacitance
When the array is used for transmitting, the
between the condenser plates ¿l5 and 55 is series
current in the central group is maintained con
resonant at the frequency of antenna operation.
stant. The current in each element of the side
The rotor plate 55 is effectively grounded by
group is 1/2' that of each element of the central
means of the stub 51 which, together with the
group, and inA one position of the switch 49, the
capacitance of the plates 5l and 55 is series
current in the side group 3 leads the current
The residual capacitances at the un
in the center group l by 25°. The current in
grounded points 29 and ¿lo are brought to par
the side group 5 lags that in the central group
by the same amount. For the opposite position 35 allel resonance by the stub lines 41 >and ¿i5 re
spectively so that these capacitances have no
of the switch ¿l5 these conditions are reversed,
net eñect on the normal transmission path
and the current in the side group 5 leads while
through the ungrounded junction point. When
that of the side group 3 lags.
the point ‘29 is grounded, current flows over the
Referring to Fig. 3, the field components re
sulting from the in-phase components of the 40 line sections ¿i3 and 39, so that the side group 5
leads the side group 3 in phase by an angle pro
antenna currents are illustrated. This ñgure
portional to the length of the line section 25.
neglects the individual directivity of the radiators
When the point 44 is grounded current flows
and the effect of the screen which will be taken
over the path including sections 2.1 and 35
into account in Fig. 4. The field component
caused by the central antenna is represented by 45 and the side group 3 leads. Thus the beam is
displaced from left to right as the rotor of the
the dotted line 55. rl‘his is seen to be independent
capacitor ¿i9 is turned. The rotor of the capaci
of the bearing angle 0. The field component
tor 49 is grounded through series resonance with
produced by the currents in the side groups 3
and 5 is indicated by the dash line 61. This is 50 the stub lines to avoid necessity for rotating
ground connections which are diiilcult to achieve
a function of the angle 9 as described above.
at high frequencies. This arrangement also pre
It is to be understood that the curve 61 repre
vents radio frequency currents from flowing
sents only that portion of the field which is
down the motor shaft and through the motor`
produced by the in-phase components of the
currents in the antennas. The resultant field
is merely the sum of the fields produced by the 55 Thus the invention has been described as an
antenna system for providing alternately over
side and center groups and is thus represented
lapping directive radiation lobes. A relatively
simple array is employed, comprising a central
Referring to Fig. 4, the resultant due to the
radiator group and two symmetrically disposed
quadrature phase components of the side antenna
groups. The central group is excited con
currents is represented by the dotted line 1|.
tinuously and the side groups are excited out
The resultant field caused by the in-phase com
of phase with the central group, one side leading
ponents, represented by the curve 69 in Fig. 3,
and the other side lagging by the same angle.
is shown by the dash line curve 13 in Fig. 4. This
The phase angles of the side groups are inter
curve is equivalent to the curve 69 but is repre
65 changed periodically to displace the radiation lobe
sented on a different scale and is extended to
from left to right. An improved switch is pro
both sides of the zero bearing axis. The direc
vided for this purpose, comprising a rotating
tivity factor produced by the use of a screen
capacitor provided with a single rotor and a plu
and the directivity of the individual radiators is
rality of stator plates. The rotor is grounded
represented by the alternate dot and dash curve
15. I. e. a single radiator, with a screen, has 70 through a series resonant circuit including the
by the solid line curve 69.
a directivity pattern like the curve 15.
To de
termine the resultant field, the quadrature and
in-phase component curves 1I and 13 are added
together graphically and multiplied by the di
rectivity factor curve 15.
capacitance to one of said stators.
We claim as our invention:
l. An antenna system for providing alternately
overlapping directive pattern lobes, lcomprising
The result of this 75 a central radiator group and two side radiator
groups symmetrically disposed with respect there
one leading, and one lagging, with currents in
each side group radiator equal to one half the
to, each of said radiator groups comprising a
pair of horizontal dipoles spaced 1/2‘ wave length
current in each center group radiator, and means
apart vertically and electrically` connected in
for periodically reversing the phase relations of
parallel, said side groups being separated hori 5 the energization of said side groups with respect
zontally from said central group by 5/8 wave
to that of said central group.
length, a main transmission line adapted to be
3. The invention as set forth in claim 1, in
connected to a utilization circuit, said trans
cluding a screen of conductive material disposed
mission line being connected directly to said
in a plane parallel to all of said radiator elements
central radiator group and through branch cir 10 and spaced substantially 1/8 wave length there
cuits to said side radiator groups, a section of
transmission line of a length equivalent to 50
4. A radio frequency distribution circuit in
electrical degrees and switching means arranged
cluding a main supply line, two branch lines,
to alternately include said line section in the
two transmission line sections 1/5 wave length
paths to said side radiator groups, said switching
long, each connecting one of said branch lines
means comprising quarter wave length trans 15
respectively to said main line, and a transmission
mission line sections connected in series between
line section of predetermined length connecting
said main line and each of said branch circuits,
said half wave transmission line sections to each
stub lines, and motor driven capacitor means
other, switching means arranged to alternately
connected to said quarter wave sections and to
short circuit said half wave length sections at
said stub lines, whereby said quarter wave sec
their midpoints, said switching means compris
tions are alternately short-l circuited through series
ing cyclically variable capacitor means connected
resonant circuits including said capacitor means
to said midpoints and stub lines connecting said
and said stub lines.
variable capacitor means to ground, said stub
2. An antenna system for providing alternately
overlapping directive pattern lobes, comprising 25 lines being of such lengths that said stub lines,
a central radiator group and two side radiator
groups symmetrically disposed with respect there
together with the maximum capacitance of said
variable capacitor, comprise series resonant cir
to, each of said radiator groups comprising a pair
of horizontal dipoles spaced 1/2' wave length apart
5. The invention as set forth in claim 4 in
from said central group by 5A; wave length, means
cuits which are parallel resonant with the mini
mum capacitance of said variable capacitor at
vertically and electrically connected in parallel, 30 cluding inductive elements connected to said
midpoints and so proportioned as to form cir
said side groups being separated horizontally
for constantly energizing _said central group.
means for energizing each of said side groups 25
degrees out of phase with said central group,
the frequency of operation of said system.
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