Radiating source formed by a dipole excited by a waveguide and an electronically scanning antenna comprising such sources

Disclosed is a radiating source formed by a dipole excited by a flat waveguide which is rectangular in section and is formed by a dielectric sheet having the shape of a rectangular prism whose major and minor faces are each covered with a metal layer of lesser length. The two major faces parallel to the longitudinal midplane are each extended toward the end of the dielectric sheet by means of a metal tongue terminating in one of the stems of the dipole. These stems may be parallel or perpendicular to the direction of polarization of the electric wave radiated by the guide.

FIELD AND BACKGROUND OF THE INVENTION 
Our present invention relates to a radiating source formed by a dipole 
excited by a waveguide of rectangular section which can be used in an 
electronically scanning antenna. 
The radiating part of such an antenna requires a large number of repetitive 
elements called modules, each formed from an elementary source and an 
associated phase shifter constituting a phase-shifting network. 
In an earlier construction, such an elementary source is formed by a dipole 
supported by a metal plate inserted into the nipped end of a waveguide by 
which it is excited. This construction has the drawback of being 
cumbersome on account of the size of the waveguide and the arrangement of 
the dipole on a metal plate. Another drawback comes from the need for 
machining and mounting operations resulting in difficulties for industrial 
production, in uncertain reproducibility and in a relatively high cost. 
OBJECT AND SUMMARY OF THE INVENTION 
With the object of remedying these drawbacks, our invention provides a 
radiating source formed by a dipole excited by an extra-flat waveguide. 
Such a construction satisfies the requirement for easy reproducibility of 
the radiating part of an electronic-sweep antenna. 
According to one feature of the invention, the waveguide exciting the 
dipole is formed from a dielectric sheet having the form of a rectangular 
prism with a longitudinal axis or centerline whose two pairs of faces 
paralleling the axis are each covered by a metal layer of shorter length. 
The two major faces parallel to that axis are each extended towards the 
end of the dielectric sheet by a metal tongue terminating in the stems of 
the dipole. 
We may, however, replace the dielectric sheet by a body of air in which 
case the waveguide will be simply a prismatic metal shell of rectangular 
cross-section. 
One of the advantages of the radiator structure according to our invention 
is the compactness of the assembly dipole and the wave guide whose size is 
not increased by the addition of a phase shifter which is associated 
therewith to form a module usable in an electronically scanning antenna. 
Another advantage is the reduction in the cost of equipment and 
technology. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description given solely 
by way of a nonlimiting illustration in conjunction with the accompanying 
drawing.

SPECIFIC DESCRIPTION 
Elements having the same reference characters in the several drawing 
Figures perform the same functions and are only described once. 
It is much simpler to feed a dipole by means of a rectangular waveguide 
than by means of a coaxial line, the electric field produced in a coaxial 
line being radial in contrast to that produced in a rectangular guide. 
FIG. 1 shows a conventional radiating source formed by a dipole 1 excited 
by a waveguide 2. The dipole is mounted on a metal plate 3 which fits into 
the opening 6 of guide 2 along the longitudinal midplane thereof. The 
stems 4 of the dipole are parallel to the direction of polarization of the 
electric field E propagated in guide 2 in mode TE.sub.01, for example. 
Since the metal plate 3 is inserted along the longitudinal plane of 
symmetry of guide 2, the two stems 4 of dipole 1 are excited in the same 
manner. The impedance matching between dipole 1 and waveguide 2 is 
achieved by nipping the end 5 of the guide and by adjusting the extent to 
which dipole 1 is inserted into the opening 6 of the guide. 
FIG. 2 shows a radiating source in accordance with the invention. It 
comprises a dielectric sheet 7 in the form of a rectangular prism of 
length L.sub.1, width L.sub.2 and height L.sub.3, having a longitudinal 
midplane .pi. and a longitudinal median axis or centerline .DELTA.. 
The waveguide 8 is formed by a portion of sheet 7 of lesser length 
(L&lt;L.sub.1) whose opposite major faces parallel to plane .pi. and opposite 
minor faces perpendicular thereto and parallel to axis .DELTA. are each 
covered with a metal plate of length L. The two metal plates 9 and 10 
parallel to plane .pi., which form the major sides of a prismatic shell 
also including a pair of minor-side metal plates perpendicular thereto, 
are each extended by a respective metal tongue 11 and 12 terminating in 
stems 13 and 14 of the dipole. The width of tongues 11 and 12 decreases 
from waveguide 8 towards stems 13 and 14 for providing proper impedance 
matching between the guide and the dipole. In this Figure, stems 13 and 14 
of the dipole are positioned flat against the end of dielectric sheet 7 
and perpendicular to the direction of polarization of electric field E 
(cf. FIG. 1) in guide 8. These stems 13 and 14 are each formed by a metal 
strip perpendicular to the matching tongues 11, 12 and integral with the 
ends thereof. The width of these metal strips is chosen with due regard to 
the need for impedance matching between the dipole and the waveguide. The 
fact that the direction of stems 13 and 14 is perpendicular to the 
direction of polarization of the electric wave emitted by guide 8 causes 
the appearance of a crossed polarization wave. In some antennae, the 
residue of crossed polarization may serve for improving detection. 
Waveguide 8, tapering tongues 11 and dipole 12 and stems 13 and 14 may be 
layers formed by metallization (e.g. cadmium plating) or photo-etching. 
FIG. 3 shows another primary radiating source embodying our invention. 
Here, stems 15 and 16 of the dipole are parallel to the direction of 
polarization of the electric field E radiated by the waveguide. As before, 
guide 8 and tongues 11 and 12 may be formed by metal plating or by 
photo-etching, but the stems 15 and 16 are metal tongues ensuring a 
certain mechanical strength. 
This radiating source may serve as an elementary radiator for an 
electronically scanning antenna. In this case the waveguide is connected 
to the output of one or more diodes forming part of the phase-shifting 
network of the antenna. In FIG. 3, phase shifters 17, 18 and 19 displacing 
the phase respectively by 3.lambda./4, .lambda./2 and .lambda./4 are each 
formed by a diode 20 placed in a hole 21 provided in the full thickness L3 
of dielectric sheet 7. This diode 20 is connected on one side directly to 
the metal plate covering one of the two major guide faces parallel to the 
longitudinal midplane and on the other side to a strip-line trap disposed 
on the opposite major face parallel to that plane so that the diode is 
grounded on both sides for ultrahigh frequency. 
A printed circuit 22 is connected to the phase shifters 17-19 for feeding 
and controlling them. The height L.sub.3 of dielectric sheet 7 is equal to 
the thickness of the diodes 20 of the phase shifters. 
FIG. 4 shows another embodiment of a radiating source in accordance with 
the invention in which the stems of the dipole have a better mechanical 
strength than in the preceding Figure. There is disposed on the matching 
tongue 11 or 12 a small dielectric substrate plate 23 in the form of a 
rectangular prism and having the same width as the corresponding tongue 11 
or 12, so that its large sides 24 and 25 are perpendicular to the 
longitudinal midplane .pi.; the small side perpendicular to plane .pi. and 
situated at the end of dielectric sheet 7 is metallized to form the stems 
26 and 27 of the dipole. 
Another embodiment of the dipole stems is shown in FIG. 5 where stems 28 
and 29 are formed by metal strip machined to a T profile; in FIG. 6 on the 
other hand, stems 30 and 31 are U-shaped. 
FIG. 7 shows an electronically scanning antenna whose elementary sources 
are constructed in accordance with the invention. All the dipoles 32 are 
oriented in the same direction which is that of the polarization of the 
antenna. At a distance equal to a quarter of the operating wavelength, 
i.e. .lambda./4, are placed reflecting members 33, 34, e.g. of aluminum 
forming the reflector of the antenna. For reasons of mechanical strength 
and ease of assembly, each row of radiators with longitudinal axes 
perpendicular to the direction of the stems of the dipoles is flanked on 
one side by a metal plate 33 whose length is equal to the height of the 
row and on the other side by metal plates 34 whose length is equal to the 
distance separating two dipoles. The antenna may have a variety of forms, 
e.g. flat or parabolic. 
Thus we have described several possible embodiments of a radiating source 
formed by a dipole fed by means of an extra-flat waveguide, of very 
reduced dimensions in relation to those of the prior art. Since no very 
expensive equipment is required and since the technical difficulties are 
not too great, the overall cost of such a source is relatively low.