April 24, 1962 e.

ROBERT-PIERRE MARl 3,031,665

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INVENTOR
GEORGES ROBERT-PIERRE MAR/
April 24, 1962 G. ROBERT-PIERRE MARl 3,031,665
WIDE BAND SLOT ANTENNA
Filed Dec. 15, 1959
2 Sheets-Sheet 2

INVENTOR

GEORGES ROBERT-PIERRE MAR/E

1 2
coaxial cable is obtained, as illustrated in FIG. 2, by
3,031,665 connecting the outer sheathing conductor 13 of said co
WIDE BAND SLGT ANTENNA axial cable with a metal stud 9 connected in its turn
Georges Rohert-Eerre Marie, Paris, France, assignor to through galvanic means 2 with the edge 6 of the slot
Societe dApplications Generales dElectricite et de
Mecanique, Paris, France, a corporation of France 1. The inner conductor 8 of the coaxial cable passes
Filed Dec. 15, 1959, Ser. No. 859,683 through a bore 3 formed in the stud 9 and extends inside
Claims priority, application France Dec. 20, 1958 a bore 4- formed in a similar stud 10 facing the stud 9,
6 Claims. (Cl. 343-470) said inner conductor 8 being connected with said stud
10 at the point 11 located at the bottom of its bore. Said
This invention relates to wide band aerials. 10 stud 10 is not connected directly with the slot edge 5
It is an object of the invention to provide an aerial but only through a polyethylene blade 12, so as to form
adapted to operate correctly on a very wide band of a condenser of a capacity C, whereby the stud 10 and
frequencies, the ratio between the extreme frequencies the edge 5 of the slot are capacitively connected. On
which may be radiated emciently by said aerial reaching the other hand, the portion of the inner conductor of
a ?gure as high and exceptional as 10, without any modi 15 the coaxial cable located inside the bore formed in the
?cation in the mechanical structure of the aerial. This stud 10 acts in association with the latter as an induc
result is obtained in accordance with the invention, chief tion coil having a value L, so that, from an electrical
ly by resorting to different methods of radiation applied standpoint, the coaxial cable 813 is connected with
in succession, without any mechanical change, when op the slot through the agency of an inductance and a ca
eration is shifted from one end of the range of frequen 20 pacity inserted in series. Of course, the inner section
cies to the other end. of the inner conductor of the cable extending between
In order to obtain said result and in accordance with the studs 9 and 16; is not surrounded by the outer con
a main feature of my invention, the improved aerial ductor.
includes primarily two radiating slots coupled in parallel The aerial thus described is generally associated with
relationship, the edges of said slots forming the points 25 a re?ector constituted by a ?at panel 14 (FIG. 2) located
through which the aerial is fed when said aerial operates at a suitable distance behind the panel 7, the size of said
as a transmitting aerial or energizing points when it 0p re?ector being larger than that of the ?rst-mentioned
erates as a receiving aerial. Furthermore, the two slots panel 7; the horizontally shaded portions shown in FIG.
are formed on the same conductive panel, including in 1 correspond to the outer section of the re?ector 114 ex
its middle a central opening which cooperates for low 30 tending beyond the edges of the panel '7 and to the section
frequencies with the system of two slots, with a view to of the reflector 14 appearing through the slot. Such a
obtaining at said lower end of the frequency range an reflecting panel may be executed in the usual manner
efficient radiation. by means or" a grid or of a system of rods.
Furthermore, and in accordance with another feature The ?eld radiated by said aerial is subjected to a lin
of my invention, there are provided, in a modi?cation, 35 ear polarization, the direction of polarization registering
two pairs of slots formed on the same panel and coop with the line connecting transversely the edges 5 and 6
erating with a central cross-shaped opening, so as to form of the slots.
the equivalent of two systems radiating each, independent Assuming the characteristic properties of the different
ly of each other, waves which are subjected to a recti elements and, chiefly, the capacity C and the inductance
linear polaiisation, the directions of polarisation for the L are suitably selected, taking into account the size of
two systems being perpendicular to each other. the slot, it is possible to obtain a satisfactory operation
My invention will be readily understood upon read of the aerial within a comparatively wide range of fre
ing of the following description of various embodiments quencies extending, for instance, between a frequency f
I. incorporating further features of interest. In said draw and a frequency 3], i.e. in a ratio as between 1 and 3.
ings: 45 For this range of operation, the matching is satisfac
FIGS. 1 and 2 illustrate a slotted aerial of a conven tory and the rate of the stationary waves does not ex
tional type, wherein the connections have been however tend beyond a value of about 2, this being ascribable,
improved, with a view to widening the pass-band, said in particular, to the parts played by the capacity and the
FIGS. 1 and 2 being respectively a plan view and a sec induction coil L.
tional view of the aerial. 60 It is a known fact that it is possible to give the sys
FIGS. 3 and 4 are a plan view and a lateral sectional tem including the slot and the feeding means a size such
view of a system of two slotted aerials fed in parallel that the aerial provides an impedance of the order of 100
and positioned on a panel including a central opening ohms across the coaxial cable. However, if it is neces
of a suitable shape, with a view to increasing the Width sary to reduce the impedance to the order of 50 ohms,
of the frequency pass-band in accordance with one of which value is preferable for obtaining an ef?cient opera
the features of my invention. tion of the feeders, a number of di?iculties arise, which
FIG. 5 is a perspective view of an aerial associating cannot readily be cut out.
two radiating systems executed in accordance with my These di?iculties may be removed by resorting to a
invention. radiating system including two slotted aerials of the type
In said drawings, the same reference numbers desig 60 disclosed and by feeding said aerials in parallel, the two
nate the same members on the different ?gures. coaxial cables of an impedance of 100 ohms being con
I have illustrated in FIGS. 1 and 2 an aerial with a nected in parallel with a common feeder of a matching
conventional slot constituted mainly by a generally rec impedance of 50 ohms, as provided by a conventional
tangular opening 1 with a constricted section, the edges T-shaped connection.
of which 5 and 6 are located in the central area of the 65 It is thus particularly easy to provide an impedance
aerial, so as to receive or to collect between them the of 50 ohms for the actual feeder, whereas the impedance
high frequency voltage which is fed to or tapped off formed by each slot considered alone is equal to 100
them by a suitable coaxial cable. Said opening or slot 1 ohms. Furthermore, the gain of such radiating systems
is formed in a metal panel 7, say of a rectangular shape, executed is substantially twice that of a single slot.
as illustrated. '
70 It is apparent that, for high frequencies, the currents
The connection between the edges of the slot 1 and the induced at the surface of the conductive panel 7 are
 3 4
localised in areas adjacent the edges of the slot; said cur opening 27 playing the same part as the slot 21 in the
rents extend gradually their operative area further and embodiment illustrated in FIG. 3.
further away from the center of the slot when the fre-> The panel 16 is in the shape of a square, the apices
quency of the voltage applied across said edges decreases of which are located at the points 50, 51, 52, 53, said
and the disturbances due to the fact that the size of the square including projecting'parts along its sides, in which
panel 7 is limited in all directions modify to a gradually projections are cut the ends of the cross-shaped slot 27
increasing extent the value of the impedance formed by extending beyond said sides.
the radiating means across the coaxial cable. The stats 17 and 18 are fed by coaxial cables 40 and
When the same metal panel is provided with two identi 41 connected with a common feeder 42, while the slots
cal slots of the type disclosed, and of which the longi 10 28 and 29 are fed similarly by the coaxial cables 46 and
tudinal axes are parallel, the longest wavelength for which 47 connected in their turn with a second feeder 48.
the system thus executed radiates in a satisfactory manner The slot 27, of which the outline is formed chie?y,
is substantially equal to twice the distance separating the as described, by two rectangles having the same center
longitudinal axes of the slots. As a matter of fact, for and shifted with reference to each other by 90, retains
the lower frequencies, the, portion of the panel extending the same shape when it is shifted angular'lyby one quarter
between the two slots radiates in the same manner as a of a revolution. It plays thus the same function with
half wave aerial energized through both ends, while the reference to the slots 28 and 29 and with reference to
impedance applied to the coaxial cable becomes then the slots 17 and 18. The re?ector associated with the
much higher than the matching impedance of said coaxial panel alsocarries the reference number 45, as precedingly.
' cable, which leads to a re?ection of the energy and to a 20 in order to make it appear more clearly, the sections of
poor efficiency. said re?ector apparent to view !are shown horizontally
It may be attempted to increase said upper limit wave shaded in FIG. 5. The apparent shifting between the
length by increasing the spacing between the two slots, front panel and the re?ector is provided by the perspec
in which case the aerial becomes too bulky and, further tive showing of the two parts.
more, the radiating diagram for the high frequencies of 25 The re?ector is obviously constituted by a metal plate
the range shows a series of lateral lobes which are much or a grid and the panel 16 is secured thereto through
too large. metal tubes or uprights perpendicular to the plane of the
In accordance with my invention, I remove both these panel and located in proximity with the edges of the radiat
drawbacks by resorting to a radiating system constituted ing slots which face away from the center of the panel.
by a single metal panel or plate 16, as illustrated in FIG. These uprights carry the reference numbers 3233 for
3 and provided with two identical slots 17 and 18, the the slot 17, 3435 for the slot 18, 36-37 for the slot
longitudinal axes of which are parallel and the spacing 28 and 38-'39 for the slot 29. They are also shown in
between which is comparatively small, while a third slot perspective view.
21 is formed in the panel 16 in its central area between As illustrated, the upright 33 is arranged symmetri
the two slots 17 and 18, the length of said slot 21 being cally of the upright 32 with reference to the transverse
substantially equal to twice the length of the slots 17 axis of the slot -17 which is perpendicular to its longitu
and 18. dinal axis, and the same is the case for the other pairs of
Experience shows that the presence of this slot 21 ex uprights. It is preferable, Without this being essential,
tends remarkably on the low frequency side the range for the distance between the axes of two adjacent up
for which the aerial thus executed is correctly matched rights, to be substantially equal to the common length
and radiates e?iciently. FIG. 3 is a plan view of such of said uprights, i.e., to the distance separating the planes
an arrangement, FIG. 4 being a sectional view thereof. of the panels -16 and 45. As a matter of fact, when the
The coaxial cables having a matching impedance equal metal tubes forming said uprights vibrate at half wave
to 100 ohms and which are connected with the slots 17 frequency and produce an electric short-circuit between
and 13 are shown in dot-and-dash lines in FIGS. 3 and 4 the panel 16 and the re?ecting panel 45,'they are located
with the reference numbers 40 and 41. Of course, the at a distance of one quarter wave from the point at which
connections between the coaxial cables and the slots are the coaxial cable energizes the cooperating slot and, con
of the type illustrated in FIG. '2. The cables are inter sequently, the presence of said uprights does not modify
connected by a conventional T-shaped connection 43 With the value of the impedance across the coaxial cable.
the feeder 42 having a characteristic impedance equal to EXperience shows that the fact of locating the uprights
50 ohms. in the manner disclosed allows cutting out the parasitic
The horizontally shaded portion of FIG. 3 illustrates the vibrations which would otherwise appear between the
sections of the re?ecting panel 45 extending beyond the panel 16 and the re?ector 45.
panel 16 or appearing through the slots. Said re?ecting On the other hand, a number of uprights serves for
panel is shown in cross-section in FIG. 4. the passage therethrough of the coaxial cables con
It is also possible, without widening the scope of the nected with the slots.
invention, as de?ned in the accompanying claims, to The distance separating the planes of the panel 16 and
modify the outline of the panel 16, as described herein of the re?ector 45 is selected, so as to obtain a correct
after with reference to FIG. 5. matching and a proper radiating diagram for the high
It is also possible to modify the outline of the central frequency section of the radiated range.
slot 21 without disturbing the operation of the system. Experience shows that towards the lower end of said
'It is possible, in particular, to give said central slot 21 range, the size of the re?ector 45 is not su?icient for
the shape of a cross. Said latter arrangement is of par obtaining a suitable directional effect for the radiating
system. .
ticular interest, since it allows using the same panel 16
for obtaining two different directions of polarisation Now, according to a further feature of the invention
through mere incorporation of two further operative slots the directional effect for the lower frequencies is improved
by locating to the rear of the re?ector 45 a second re
fed independently of the two former and extending per
?ector, the action of which is limited, in practice, to the
pendicularly to the ?rst-mentioned operative slots, as pro lower frequencies. Said second re?ector may be con
vided in accordance with a further feature of the inven 70 stituted very simply by rods such as 26 for the polarisa
tion. tion of the waves radiating by the slots 17 and 18 and
Said arrangement is illustrated in FIG. 5 showing a by rods perpendicular to the former and which are not
panel 16 of the type illustrated in FIG. 3 and provided illustrated for the waves radiated by the slots 28 and 29.
with two pairs of operative slots, respectively at 17-18 From a mechanical standpoint, and for sake of an
and 2829 in association with a central cross-shaped 75 easier transportation, it is of advantage that, except for
 3,031,665
5 6
the rods such as 24- and 25, referred to hereinafter, and erence to two perpendicular axes drawn on said plate,
as 25, which may be readily of a removable type, the the slots of each pair being fed by the coaxial cables of
mechanical system including the radiating panel 16 and the corresponding pair and the plate being further pr -
the re?ector does not project outside a geometrical paral vided with a central cross-shaped slot, the arms of which
lelopipedon having for its base the square, the apices of are equal and symmetrical and extend along the bisecting
which are designated by 50, 51, 52, 53. To reach this lines of said perpendicular axes.
result and in accordance with a still further feature of 3. An aerial adapted to radiate satisfactorily through
the invention corresponding to a modi?ed embodiment, out a very Wide range of frequencies, comprising two
the sections of the panel 16 extending beyond said square feeders, a pair of coaxial cables fed by each feeder and
are advantageously folded back by 90 rearwardly in 10 a plate provided with two pairs of symmetrical slots,
planes perpendicular to the plane of the front panel. Con the slots of said pairs being arranged symmetrically with
sequently, a fraction of the two rectangles forming the reference to two perpendicular axes drawn on said plate,
central slot 27 is also folded back. the slots of each pair [being fed by the coaxial cables
Under such conditions, and if the size of the re?ector of the corresponding pair and the plate being provided
45 is the same as that of the square having its apices at 15 with a central cross-shaped slot, the arms of which are
50, 51, 52, 53, it is found that there is a mismatching for equal and symmetrical and extend along the bisecting
frequencies such that the length of the diagonal of the lines of said perpendicular axes, a re?ector plate paral
square 56, 51, 52, 53 approximates an integral number lel with the slotted plate and lying at a small distance be
of half Wavelengths of the radiated waves. hind the latter and a pair of tubular members intercon
In order to cut out this drawback, and in accordance 20 necting the two plates near the outer edge of each of
with a last feature of my invention, the re?ector is asso the ?rst-mentioned slots. arranged pairwise and into which
ciated with rods extending along said diagonal beyond its members the corresponding coaxial cables extend to feed
apices. Said rods, illustrated at 24-25 and 39-31, have the cooperating slot, the spacing of the tubular members
lengths which are substantially equal to one half that of of each pair being substantially equal to the spacing of
the diagonal of said square. Their presence clamps the 25 the plates.
vibrations of the re?ector 45 for wavelengths correspond 4. An aerial adapted to radiate satisfactorily through
ing to a mismatching. As a matter of fact, for such out a very wide range of frequencies, comprising two
waves, the re?ector vibrates at half-wave frequency and feeders, a pair of coaxial cables fed by each feeder, a
shows an impedance, which is in?nite, at the apices of plate provided with two pairs of symmetrical slots, the
the square. The rods such as 24--25 vibrate thus at 30 slots of said pairs being arranged symmetrically with
quarter Wave frequency and show at said apices their own reference to two perpendicular axes drawn on said plate,
radiating impedance which is of the order of 72 ohms, the slots of each pair being fed by the coaxial cables
which cuts out the resonance leading to such a mismatch of the corresponding pair and the plate being provided
ing of the system. with a central cross-shaped slot, the arms of which are
It should ?nally be remarked that the radiating system 35 equal and symmetrical and extend along the bisecting
thus constituted is generally carried by a metal mast, lines of said perpendicular axes, a re?ector plate lying in
through the agency of securing means ?tted on the re parallelism and at a small distance to the rear of the
?ector panel 45, said securing means being preferably latter, and a mast carrying the two plates horizontally
located in an area adjacent the center of said re?ector above ground.
panel. 5. An aerial adapted to radiate satisfactorily through
When a metal mast is resorted to for carrying the out a very wide range of frequencies, comprising two
aerial, it is possible to cut out the vertical rods such as feeders, a pair of coaxial cables fed by each feeder, a
26, since the metal mast forms an advantageous substitute plate provided with two pairs of symmetrical slots, the
therefor. slots of said pairs being arranged symmetrically with
Experience has shown that an aerial of the type con 45 reference to two perpendicular axes drawn on said plate,
sidered, the sides of which measure 1.28 meter, provides the slots of each pair being fed by the coaxial cables of
at satisfactory radiation of the waves, the frequencies the corresponding pair and the plate being provided with
nerv of which range between 90 megacycles and 950 mega
cycles, the rate of the stationary waves lying for all the
a central cross-shaped slot, the arms of which are equal
and symmetrical and extend along the bisecting lines of
frequencies inside said range underneath a value equal 50 said perpendicular axes, a re?ector plate lying in paral
to 2.3. lelism and at a small distance to the rear of the latter,
Obviously, many details may be modi?ed in the em and auxiliary re?ector rods extending perpendicularly to
bodiments disclosed, chie?y as concerns the auxiliary each of the perpendicular axes.
mechanical supports of insulating material which may be 6. An aerial adapted to radiate satisfactorily throug
incorporated for increasing the mechanical resistance of 55 out a very wide range of frequencies, comprising two
the system, without unduly widening thereby the scope feeders, a pair of coaxial cables fed by each feeder and
of the invention as de?ned in the accompanying claims. a square plate provided with two pairs of symmetrical
In FIG. 5, the arrows drawn inside the cross-shaped slots, the slots of said pairs being arranged symmetrically
central slot 27 de?ne the structure of the electrical ?eld with reference to'two perpendicular axes drawn on said
inside said slot. 60 plate, the slots of each pair being fed by the coaxial
What I claim is: cables of the corresponding pair and the plate being
1. An aerial adapted to radiate satisfactorily through provided with a central cross-shaped slot, the arms of
out a very Wide range of frequencies, comprising at least which are equal and symmetrical and extend along the
one feeder, a pair of coaxial cables fed by said feeder bisecting lines of said perpendicular axes, said slotted
and a plate provided with at least one pair of symmetri 65 plate being folded back across the ends of the arms of
cal slots fed by the coaxial cables of the corresponding the slot, a square re?ector plate lying in parallelism with
pair and with a central slot extending symmetrically be the slotted plate and at a small distance behind the folded
tween the slots of each pair and substantially longer than parts of the latter and the sides of which are equal to
the latter, and a re?ector plate parallel with the slotted those of the slotted plate, and rods carried by each apex
plate and lying at a small distance behind the latter. 70 of the re?ector plate and the lengths of which are equal
2. An aerial adapted to radiate satisfactorily through to one half the diagonal length of the latter.
out a very wide range of frequencies, comprising two References Cited in the ?le of this patent
feeders, a pair of coaxial cables fed by each feeder and
UNITED STATES PATENTS
a plate provided with two pairs of symmetrical slots, the
slots of said pairs being arranged symmetrically with ref 75 2,660,674 Brown _____________ _.. Nov. 24, 1953