Abstract: An antenna excited by a symmetrical strip line (1) including two peripheral conductors (3, 3') positioned respectively above and below a central conductor (2). It comprises, at the end of the symetrical strip line, a first dipolar radiating element (10), including two quarter wave branches (11, 11') formed by extending each of the peripheral conductors (3, 3') in their plane and a quarter wave branch (12) formed by extending the central conductor (2) in its plane, in an opposite direction; a second dipolar radiating element (20), orthogonal to the first one, including two quarter wave branches (21, 22) formed by the folding of the cental conductor (2) and of one (3) of the peripheral conductors; and distributor and phase-shifter means (30) to excite the dipolar radiating elements (10, 20) by similar respective signals, having the same amplitude but being phase-shifted by 90.degree..

Abstract: An antenna system capable of both circular and linear polarization. The antenna structure includes a symmetrical stripline 90.degree. hybrid coupler, having first and second output branches. A first and second dipolar radiating element is provided, each of the radiating elements having two quarter wave branches formed by folding the stripline conductors. In the first dipolar radiating element, the peripheral conductors of the stripline coupler are folded in the same direction, transverse to the axis of the stripline, and another quarter wave branch is formed by extending the center conductor of the first output branch of the hybrid coupler in an opposite direction. The second dipole radiating element is similarly configured to have two quarter wave branches, comprising the peripheral conductors and the center conductor of a second output branch of the 90.degree. coupler. A second 90.degree.

Abstract: The I.F.F. sum and difference channels are obtained by means of the reflector of the radar, illuminated by primary radiating elements associated with the horn of the primary source of the radar. Furthermore, the signals of the I.F.F. sum and difference channels are suitably mixed to obtain a reduction in the level of the cross-polarized signals.

Abstract: Disclosed is a loop type antenna, fed by a coaxial line, comprising:a symmetrical, plane, loop-shaped radiating element enclosed on itself, connected to the core of the coaxial feed line at one point of the loop;a reflector plane extending in parallel to the plane of the loop and at a distance from it; and,a symmetrizer element in the shape of a metallic plate, placed between the loop and the reflector and extending in parallel to the plane of the loop and to that of the reflector plane, with a general shape substantially corresponding to the shape of that portion of the loop which is connected to the core of the coaxial line, this plate being connected to the ground of the coaxial feed line. The disclosure also concerns an array antenna comprising an ordered grouping of several antennas, excited simultaneously, said loop and said plate of each antenna extending over a common reflector plane.

Abstract: A conical sweep array antenna has a flat antenna structure having a plurality of microstrip sources disposed in a plurality of sections. Preferably, each section includes a plurality of sources. The flat antenna also has at least one source disposed outside any of the sections. A phase-shifting device phase-shifts the plurality of sources to cause a conical sweep pattern of the flat antenna. Also, the phase-shifter device provides a constant phase-shift to the one source which is not disposed in any section. The presence of the nonphase-shifted source improves the radiating diagram of the antenna of the invention, particularly by reducing the coma lobe.

Abstract: A microwave reflector having metallic surfaces and nonmetallic surfaces is perfectly reflecting for the waves of a first polarization and partly transparent for the waves of a second polarization orthogonal to the first. The reflector is primarily applicable to radar systems.

Abstract: A microwave primary source with a phase conical scan having a conical horn containing an obstacle which gives rise to a wave that propagates in the TE.sub.21 mode in quadrature with the TE.sub.11 fundamental mode in the opening of the horn; the obstacle is driven in rotation round the axis V of the horn.

Abstract: An antenna having two crossed cylindro-parabolic reflectors in which the generatrices of said reflectors are orthogonal. The source is placed close to the center of the main reflector, which is further provided with polarization rotation means. The auxiliary reflector is placed facing the main reflector and it is such that it is transparent to a wave polarized linearly in one direction and reflecting to the waves polarized in an orthogonal direction.

Abstract: A device for exciting a corrugated ultra-high frequency source of revolution operating in two remote frequency bands, decoupled mechanically from the source. The device includes two excitation devices corresponding to the two operating bands, placed perpendicularly to each other, at respective distances from the mouth of the source such that the waves which they emit remain canalized in the Rayleigh zone of each device and provide optimum coupling between these device and the source.

Abstract: A two-band multimode microwave source for an antenna of a low-elevation-tracking radar comprises a higher-frequency section nested in a lower-frequency section, the two sections having E-planes perpendicular to each other. The lower-frequency section includes two outer pairs of waveguides separated by a block which convergingly projects beyond their output ends and is bisected by the E-plane of that section. The higher-frequency section includes two inner pairs of waveguides disposed within that block and separated by an obstruction lying in the last-mentioned E-plane. The higher-frequency wave emitted by the inner waveguides is made planar by a lens disposed at n output aperture of the structure which is transparent to the lower-frequency wave.

Abstract: A multimode ultrahigh-frequency source with wide passband comprises a rectangular waveguide with a cavity terminating at an exit aperture in a horizontally flared horn, an input end of the cavity remote from the horn being joined at a transverse discontinuity plane to an upper and a lower pair of symmetrically disposed rectangular supply guides that are vertically separated from each other. An obstruction in the form of a block located between the levels of the supply guides extends from the discontinuity plane forward into the cavity and converges toward the horn in the vertical E-plane, e.g. with a trapezoidal cross-section. With the supply guides excited in the basic TE.sub.10 mode, a suitable dimensioning of the block will maintain a cophasal relationship between this basic mode and a hybrid mode EM.sub.12, originating at the discontinuity plane, in the exit aperture of the cavity over a wide frequency band.

Abstract: A radar antenna of the Cassegrain type comprises a paraboloidal principal reflector confronting a hyperboloidal or flat auxiliary reflector of smaller radius directing linearly polarized radiation from a source on their common axis toward the principal reflector along lines passing through the focal point thereof to produce an axially extending outgoing beam whose central part is intercepted by the auxiliary reflector. The latter consists of an array of linear conductors generally parallel to the direction of polarization while the principal reflector is formed by another conductor array generally inclined at 45.degree. to that direction, the latter array being backed by a solid mirror separated therefrom by a distance smaller than a quarter wavelength at the midfrequency of the emitted radiation.

Abstract: An antenna system of the Cassegrain type, used with a tracking radar and adapted to conically scan incoming waves reflected by outlying targets, comprises a paraboloidal main reflector and two hyperboloidal auxiliary reflectors confronting same. One of the auxiliary reflectors is semitransparent and coaxial as well as cofocal with the main reflector whereas the other is solid with an axis inclined to that of the main reflector about which it rotates while keeping its foci in the focal planes of the semitransparent reflector.

Abstract: A mixed E-plane and H-plane multimode monopulse feed is formed by a multimode E-plane horn structure, in the aperture of which metal bars or plates are arranged parallel to the electrical field. The bars or plates form discontinuities at which an odd mode of the H.sub.30 type is generated, the feed as a whole thus becoming a multimode H-plane structure. Such a feed is very useful for the production of multimode monopulse antennas of reduced dimensions.

Abstract: An antenna of the discone type is omnidirectional in bearing and has a diagram whose directivity in elevation can be adjusted. At the apex end of each cone a dielectric disc of predetermined thickness is inserted parallel to the base of the cone concerned. In the central portion of the antenna these two discs create conditions for the propagation of energy which are different from those existing outside the discs, the result being an improvement in the phase pattern in the radiating aperture of the antenna.