Abstract: A two-dimensionally steered antenna system (40) includes a planar lensing system (64, 94) operable to focus signals received from a plurality of ground-based cells (20). A first steering system (66) is operable to steer a beam (32) for each ground-based cell (20) in a first direction by weighing signals associated with the ground-based cell (20) based on a position of the antenna system (40) relative to the ground-based cell (20) in the first direction. A second steering system (96) is operable to steer the beam (32) for each ground-based cell (20) in a second direction by weighing signals associated with the ground-based cell (20) based on a position of the antenna system (40) relative to the ground-based cell (20) in the second direction.

Abstract: A wideband antenna element includes a conductive plate parallel to, and spaced from a ground plane. A tapered dielectric material is positioned between the plate and ground plane. A pair of driving points to the plate are positioned fixed distances on either side of a center interconnect point between the plate and ground plane, to effect staggered tuning of the antenna element.

Abstract: A Rotman lens (12, 13) includes a first insulating layer (26) having a high dielectric constant and a second insulating layer (46) having a low dielectric constant. Metalization provided on the first insulating layer includes a lens portion (28), and metalization provided on the second insulating layer includes a plurality of transmission lines (48) and bootlace lines (52). A plurality of via openings are provided through at least one of the insulating layers, and each contain conductive material (33, 38) which electrically couples the lens portion to a respective one of the transmission lines or bootlace lines. A number of the bootlace lines physically overlap the lens portion, without electrical engagement therewith. A ground plane (63) on a further insulating layer (61) may be provided between the first and second insulating layers, in a manner free of electrical contact with the conductive material in the via openings.

Abstract: An antenna for utilization in a fuse of an artillery shell or the like. The antenna includes a dielectric disk having upper and lower surfaces, a radiator disposed on the upper surface of the dielectric disk, a ground plane disposed on the lower surface of said dielectric disk, and a plurality of spaced apart apertures radially disposed through the dielectric disk for coupling the radiator to the ground plane.

Abstract: A planar antenna that includes a high dielectric constant superstrate lens having a plurality of air holes that vary the actual dielectric constant of the lens to provide an effective dielectric constant superstrate lens. The holes can take on any shape and configuration in accordance with a particular antenna design scheme so as to optimize the effective dielectric constant for a particular application. In one particular design, the holes are formed in a random manner completely through superstrate lens, and the holes have an opening diameter less than 1/20th of the operational wavelength of the antenna. The holes act to vary the dielectric constant of the superstrate lens so that the resonant waves do not form in the lens, thus reducing power loss in the antenna. The holes are formed by a suitable mechanical or laser drilling operation.

Abstract: Varying the azimuth and elevation beam patterns for an antenna. For a horn-type antenna implemented by a parallel-plate waveguide structure, an input port can accept an electromagnetic signal and an output slot can transmit the electromagnetic signal. An azimuth lens can be placed proximate to the output slot for adjusting the antenna beam pattern within the azimuth plane. The azimuth lens comprises two or more lens elements, each typically having a cylindrical shape and comprising a dielectric material, which support the generation of discrete beams in the azimuth plane in response to the electromagnetic signal output by the output slot. These discrete beams can sum in-phase to form a composite beam having a shape or pattern generally defined by the characteristics of the azimuth lens elements. Specifically, this composite beam has a pattern within the azimuth plane defined by the size and shape of the azimuth lens elements and the spacing between these elements.

Abstract: A sectored antenna system has one or more dielectric lenses, each having a surface and two or more antenna feed devices tilted non-parallel to the lens surface and preferably angled in a V pattern. At least one of the feed devices radiate signals into said lens that emerge as separate directional beams, or the lenses receive incoming signals from different directions and focus them onto different antenna feed devices. The feed devices of the sectored antenna system have a dielectric constant of between about 5 and 15 and preferable about 10 and further has a mounting collar to mount the antenna feed devices about the lens to adjust for elevation, azimuth, radial and rotational orientation.

Abstract: An antenna lens, in particular for a motor vehicle radar system, has in a plane perpendicular to the optical axis of the antenna lens at least a first and a second lens region, the lens regions being configured such that electromagnetic waves are concentrated or scattered in a first manner upon passage through the first lens region and in a second manner upon passage through the second lens region. The lens regions have different polarization-dependent permeabilities for electromagnetic waves. A motor vehicle radar system having an antenna lens of this kind is also described.

Abstract: In a device for directional transmission and/or receiving of electromagnetic waves, including at least one antenna element and a dielectric lens, there is arranged between them a prefocusing dielectric body for avoiding overradiation of the lens. In order to simplify adjustment, the lens has an extended surface, is preferably pot-shaped, and forms, in conjunction with a baseplate, a hermetically sealed housing for unencapsulated ICs.

Abstract: A lens is fabricated of an array of parallel rod-shaped dielectric waveguides extending from a generally planar front surface of the array, this front surface constituting a front surface of the lens, to a concave back surface of the array, this back surface constituting a back surface of the lens. The wavguides vary in length, from a maximum length at an outer region of the lens to a minimum length at a central region of the array, to provide the concave back surface. The back lens surface envelops a receptor of radiant energy located at a focus of the lens. This configuration of lens provides an increased spherical angle of impingement of the incident radiation upon the receptor.

Abstract: An electromagnetic lens comprises two conductive sides between which there is arranged a cavity provided in its lateral portion with electromagnetic input/output coupling transitions to authorize a set of propagation laws between pairs of such inputs/outputs. Moreover, it comprises, substantially centered in the cavity, a substrate comprising a printed conductive patch of predetermined dimensions, so that the two conductive sides and the patch thus create a suspended three-plate strip line structure. The content of the cavity and the respective geometries of the cavity and of the conductive patch are chosen to comply with the propagation laws.

Abstract: A lens antenna is disclosed which comprises a conical horn and a lens attached to an aperture of the horn. The lens has a first planar surface at a first side which faces free space and a hyperboloid of revolution at a second side opposite the first side and is made of a dielectric material with relative permittivity ranging from 2 to 4. The lens is provided with a cylindrical portion which has a second planar surface parallel to the first planar surface and displaced from the first planar surface by a predetermined distance. The cylindrical portion being concentric with the lens.

Abstract: A wideband lens antenna lens of reduced thickness includes a lens antenna constructed of a flat inhomogeneous dielectric plate. A radiation source is located on one side of the dielectric plate and a reflector is located on another side of the dielectric plate opposite the radiation source. In operation, signals generated by the radiation source of arbitrary polarization pass through the dielectric plate, are reflected by the reflector, and pass back through the dielectric plate a second time before being emitted from the lens antenna. In such a case, the provision of the reflector allows the thickness of the dielectric plate to be cut in half as compared with conventional lens antennas. If the signals supplied by the radiation source are linearly polarized, a polarization transformer is provided on the same surface of the dielectric plate as the radiation source.

Abstract: The invention relates to an antenna system which is capable of producing multiple, high-gain, independently steerable antenna beams from a single antenna aperture. The system accomplishes this, in part, by utilizing a separate phased array antenna as the feed element of a spherical lens for each desired beam. In this fashion, the beam(s) produced by the antenna system can each be electronically steered (independently of the other beams, if any) and physical movement of the feed element(s) is not required. The invention may also use multiple spherical lenses, wherein each lens includes at least one phased array feed.

Abstract: An array of hemispherical dielectric lenses antenna on a ground plane for focusing radiation from an array of point sources, each point source being located adjacent to its respective hemispherical lens. Dual polarization point sources provide dual orthogonally polarized radiation patterns, including right and left hand circularly polarized radiation patterns. The entire antenna and ground plane may be rotated and the array of point sources may be moved relative to the hemispherical lenses so as to scan the antenna beam over a hemisphere.

Abstract: A semi-cylindrical dielectric lens antenna on a ground plane for focusing radiation from a line source adjacent to the semi-cylinder. Grooves in the surface of the ground plane modify the polarization of the electromagnetic radiation reflected by the ground plane thus allowing conversion of radiation from linear to circular polarization and vice versa. Selectable line sources may be used to provide both right and left hand circularly polarized radiation. The entire antenna and ground plane may be rotated and the line source may be moved relative to the dielectric lens so as to scan the antenna beam over a hemisphere.

Abstract: A radiation sensor (10) for the microwave and millimeter-wave regions incorporates a lens (12) having two parallel focal planes (26a, 36), these being defined by a polarization-selective reflecting PIN diode array (18) within the lens (12). One focal plane (26a) is occupied by a receive array of crossed dipole antennas which mixes receive signals and a local osicllator signal to produce intermediate frequency signals for subsequent processing. The second focal plane (36) is occupied by a transmit antenna array of separately activatable polarization switching antennas arranged to define a range of transmit beam directions. A second PIN diode array (20) protects the receive antenna array from the transmit beam.

Abstract: An improved spherical gradient lens and a method of fabricating same. A uniform sphere of a material such as high density irradiated polystyrene or a methylpentene copolymer in the polyolefin family having a uniform relative dielectric constant is provided. A plurality of radially extending holes are formed therein, for example by drilling, the holes having a predetermined cross sectional geometry along axes extending radially from the center of the sphere. The geometry of holes is selected to control the resultant local density of material, and thus the relative dielectric constant as a function of distance from the center of the sphere. Hole diameters are chosen so as to be small compared to the shortest wavelength of interest with which the lens will be used.

Abstract: A radar lens 14 is made from a conventional Fresnel lens 10, but replaces the conventional curved surface 32 with a stepped approximation thereto 22, 24, 26, preferably of three steps. The thickness of the stepped lens 14, at each step, is a half-wavelength or a multiple half-wavelength of the radar operating frequency in the medium of the lens 14. The half-wavelength or multiple half-wavelength separation of the steps 22, 24, 26 causes reflections from the front 16 and rear 18 surfaces to cancel, thereby minimizing the (undesirable) standing wave between the lens 14 and the feed horn or feed horns 46, 48, 50. This avoids the necessity of reducing the standing wave by presenting the curved or stepped side 18 forward. The planar side 16 of the lens 14 (unlike the stepped side 18) doesn't need to be protected from road debris. The lens 14 can therefore be molded as an integral unit of a radome, desirable in the automotive setting.

Abstract: The spherical dielectric lens with variable refractive index contains modules (1, 4, 7, 9, 12) connected with one another and made from homogeneous dielectric materials with various .di-elect cons. values, which are arranged in accordance with the given principle of change in dielectric permittivity .di-elect cons. from the radius value (r) of the lens, uniquely corresponding to the rule of variation of its refractive index (n). The modules (1, 4, 7, 9, 12) of the interior layers, which form the central cubic core, are inscribed in a sphere, are of cubic form and are equal in size, while the exterior modules (1, 4, 7, 9, 12) have an outer surface of spherical form, where the latter interior layer modules (1, 4, 7, 9, 12) fill out the central core up to the sphere.

Abstract: A scanning array antenna employs a solid rotating core having an anisotropic refractive index within an apertured waveguide that emits radiation in response to an input beam propagating through the waveguide. Rotating the core changes its refractive index relative to the input beam, causing the radiated beams to undergo an angular scanning. The solid rotating waveguide core can be formed from a dispersion of aligned elongate conductive members in an isotropic dielectric, from a liquid crystal medium, or from a dispersion of aligned elongate conductive members in a liquid crystal medium. The antenna is operable in reciprocal transmission and reception modes.

Abstract: The disclosure relates to ferroelectric and superconducting thin films used in combination to produce low-loss passive microwave and millimeter wave devices which are frequency tuneable. Various metal oxide superconducting and ferroelectric thin films can be deposited in numerous multilayer geometries via a variety of deposition techniques to produce devices which can manipulate microwave and millimeter wave signals through the application of voltage bias signals across the ferroelectric films. Numerous superconducting microwave and millimeter wave devices, including delay lines, phase shifters, resonators, oscillators, filters, electrically-small antennas, half-loop antennas, directional couplers, patch antennas, and various radiative gratings, are made frequency-tuneable by utilizing voltage-tuneable capacitor structures fabricated from voltage-biased ferroelectric thin films.

Abstract: A stepped beam transmit antenna that comprises a feed array that includes a dielectric substrate and a plurality of radiating elements disposed on the substrate. The radiating elements each comprise two coplanar and coextensive fins that are separated by a narrow gap and that are tapered at their radiating end to form a linear tapered slot feed aperture. Beam position inputs are disposed at respective input ends of each of the radiating elements. A backshort is disposed adjacent the tapered slot feed aperture of each of the radiating elements. A low pass filter is disposed adjacent the backshort of each of the radiating elements. A switching diode is disposed between the backshort and the tapered slot feed aperture of each of the radiating elements. The antenna includes a power distribution network comprising a suspended printed line. A lens is disposed adjacent the feed array for projecting energy beams produced by the antenna.

Abstract: A zone plate focusing radiation comprises a plurality of surface portions (20a, 20b, 20c, 20d, 30) corresponding to zones of the zone plate. The surface portions are positioned in a plurality P of parallel planes such that each surface portion diffracts radiation out of phase with respect to adjacent surface portions such that radiation diffracted by the surface portion constructively interferes at a focus of the zone plate. The p.sup.th plane is dielectrically spaced from the first plane by n.lambda., where .lambda. is the wavelength of the radiation and n is an integer.

Abstract: An antenna system capable of receiving electromagnetic radiation having either right or left helical polarization, and either vertical or horizontal linear polarization includes an energy concentrator which concentrates energy at a focal point. A helical antenna is arranged in the proximity of the focal point. A first switch switches the helical antenna to a backfire mode of operation and a second switch switches the helical antenna to an end fire mode of operation. A control mechanism controls the switches to select the nature of the polarization.

Abstract: A method for making a material with an artificial dielectric constant is carried out by choosing the desired dielectric constant for a particular electromagnetic field, selecting a substantially non-electrically conductive sheet material (2) from which the cellular core material (26) is to be made, applying an electrically conductive material (8) to selected areas on the sheet material and thereafter forming a cellular core material from layers of the sheet material having the conductive material already applied thereto.

Abstract: An improved bandpass frequency selective surface is disclosed which provides a wide pass band and reflection band with low loss at varying angles of incidence, low cost, low volume and light weight. The improved bandpass frequency selective surface of the present invention includes a mesh-patch array 10 disposed on at least a portion of a surface wherein the mesh-patch array 10 includes a square grid 12 surrounding numerous squares 20, 21, 22 and 23. A specific teaching of the invention concerns the design of the elements of a mesh-patch array 10 such that the frequency selective surface transmits or reflects the desired microwave signals.

Abstract: A millimeter wave antenna capable of electronic scanning for automobile collision avoidance radar. The antenna includes a linear ferrite loaded slot array which illuminates a dielectric lens. The antenna system has no moving parts. Beam scanning is achieved by controlling the bias magnetic field along the ferrite rod of the slot array.

Abstract: A hybrid structure comprising a lens 10, an antenna array 8 and a semiconductor microcircuit 2. The antenna array 8 is formed on a surface of the lens 10 or on a surface of a substrate 14 having substantially the same refractive index as the material of the lens 10. Metal bump bonds 6, 12 provide connections between the antenna array 8 and the semiconductor microcircuit 2.

Abstract: A lightweight radar reflector comprising two converging lenses (21 and 22) with a reflecting surface (26) applied to the outer convex surface of one of the lenses. The lenses are preferably meniscus lenses provided with peripheral mating flanges (24 and 25) for assembly. In one form the lenses are moulded from a mixture of silica powder and polyester resin to give a dielectric constant of 3.414 for each lens. In one arrangement there may be provided means to allow the lenses to be set to a predetermined separation so that the radar reflectance of the combination can be adjusted. In a further form the lenses may comprise thin shells of polycarbonate filled with silica powder to produce the desired dielectric constant.

Abstract: The EHF omnidirectional antenna system (10) includes a shaped lens (12) that is illuminated by a corrugated horn (14). The lens is disposed in the far-field of the horn and has two shaped surfaces (20 and 30) which together disperse the beam from the horn, such that a nearly uniform coverage over hemispherical coverage area is achieved at a frequency of approximately 44 GHz. The method of making the lens utilizes a surface shaping analysis to develop the shaped surfaces of the lens. A surface matching layer (44) is applied to all surfaces of the lens to reduce surface reflection.

Abstract: Absorber elements for reducing electromagnetic leakage radiation, in particular in the vicinity of horn antennas, are in the form of ribs with a roof- or wedge-shaped cross section arranged such that the angle enclosed by lateral surfaces of the absorber elements is less than 90.degree., so that at least the leakage radiation impinging in general parallel to the center plane of the absorber elements arrives at a large angle of incidence, i.e. glancingly. In particular, if the angle of incidence approximately corresponds to the Brewster angle, the result is an almost complete absorption of the corresponding polarization components of the leakage radiation. The absorption effect can be further optimized by proper selection of the configuration of the roof- or wedge-shaped absorber elements.

Abstract: Dielectric composites are produced by incorporating metallized particles having a high aspect ratio, such as metallized phospholipid tubules, in a polymeric and/or ceramic matrix and curing or sintering in an electric, magnetic, or flow field to align the particles. The resulting composites have extremely anisotropic properties and high dielectric constants. These composites can be used, for example, in EMI shielding and microwave applications.

Abstract: Receiver apparatus for receiving electromagnetic target radiation polarized in a first direction includes a dielectric lens having forward and rearward surfaces. The received target radiation is refracted at the forward surface and reflected by the rearward surface. An antenna array is disposed adjacent one of the forward and rearward surfaces for receiving (a) the target radiation reflected from the rearward surface, and (b) a local oscillator beam haivng a polarization direction which is orthogonal to the polarization direction of the target radiation received at the antenna array.

Abstract: A transition includes a sheet of dielectric material having two parallel surfaces. A tapered recess in one surface converges towards the other surface with the axis of the recess orthogonal to said surface. The dielectric material has a critical angle of reflection with respect to the axis.A RF horn is located in proximity to the surface with the recess and has an axis in common with the axis of the tapered recess. A RF lens is located between the horn and the tapered recess. The optical properties of the RF horn, RF lens, tapered recess, and dielectric material are such that all rays traced from the horn through the lens and dielectric material to the second surface have an angle with respect to said normal of the second surface greater than said critical angle. RF energy on the second surface from the center of the horn is in phase with RF energy on said second surface from the edge of said horn allowing a surface wave to be launched on the second surface.

Abstract: A radiation sensor for centimeter, millimeter or sub-millimeter waveband receiption, comprising a metal antenna located close to a supporting dielectric body of intermediate to high dielectric constant value and having a mixer located in between and connected to the limbs of the antenna. The supporting body may itself be of semiconductor material, or if of insulating dielectric material, semiconductor material may be incorporated adjacent the antenna; and the mixer components, diodes, integrated in the semiconductor material. Antennae, as above, may be arranged in close-packed array, and the supporting body configured as, or as part of, a lens.

Abstract: An electromagnetic radiation sensor for use at microwave frequencies compes a sheet substrate bearing an array of dipolar antennas. The antennas have respective mixer diodes connected between adjacent dipole limbs, and the antenna array is located in the focal plane of a dielectric lens. Individual antenna center positions correspond to different beam directions for radiation incident on the lens, and the antenna center positions are in accordance with the Rayleigh resolved spot criterion. The dimensions, dielectric properties and relative positioning of the lens and substrate are such as to provide for the antennas to couple predominantly to radiation passing through the lens. The substrate thickness may lie between the lens and antenna array, or alternatively the array may lie between the substrtate and lens. In the latter case, the lens is of higher dielectric constant material than the substrate, at least in the lens region adjacent the array.

Abstract: A multi-layered structure utilizes two impedance matching layers 4 and 6 and a base member 2 to provide an optimal transmission characteristic for double impedance matching layer structure. The multi-layered structure provides for optimal transmission of an electromagnetic signal for wide angles of incidence, and displays minimal sensitivity to the polarization of the signal.

Abstract: An antenna includes a sheet of dielectric material having two parallel surfaces. A tapered recess in one surface converges towards the other surface with the axis of the recess orthogonal to said surface. The dielectric material has a critical angle of reflection with respect to the axis. A RF horn is located in proximity to the surface with the recess and has an axis in common with the axis of the tapered recess. A RF lens is located between the horn and the tapered recess. The optical properties of the RF horn, RF lens, tapered recess, and dielectric material are such that all rays traced from the horn through the lens and dielectric material to the second surface have an angle with respect to said normal of the second surface greater than said critical angle. RF energy on the second surface from the center of the horn is in phase with RF energy on said second surface from the edge of said horn allowing a surface wave to be launched on the second surface.

Abstract: An antenna system and technique for laminating a dielectric substrate 14 to an antenna housing 12 which prevents separation of the dielectric substrate 14 from the housing 12. This is accomplished by confining an antenna assembly 10 inside a laminating fixture 24. Heat is then applied to the fixture 12. This causes the dielectric substrate 14 to become somwhat plastic and also to expand. This expansion results in great pressure being exerted between the dielectric 14 and the housing 12. When the assembly is allowed to cool the dielectric 14 adheres to the housing 12. This prevents separation of the housing 12 from the dielectric 14. The result is an antenna assembly 10 which can withstand large temperature extremes without causing an air gap between the dielectric 14 and the housing 12 which would distort the electrical signal transmitted or received by the antenna.

Abstract: A passive radar target comprises a sond lens (50) of substantially uniform dielectric constant, having a reflecting surface (51) integrally formed therewith, the lens being constructed of particulate material having a dielectric constant selected such that radar waves striking the surface of the surface of the lens are focussed on the reflecting surface. In one form the particulate material comprise silica flour (91, 101) contained within a thin radar transparent polycarbonate shell. The shell is formed of two similar halves (102, 103) with a pressed aluminum reflective lining (92, 106) in one half. By making the lens axially symmetrical such that the forward and rearward surfaces have a radius of curvature that decreases with distance from the axis of symmetry (102, 103) the lens-reflector can be made to operate over a wide solid angle.

Abstract: A new and improved fused silica radome is discussed. The radome has a density equal to or greater than 95 percent of theoretical density, an average bend strength equal to or greater than 10 Kpsi, a thermal expansion of about 0.3.times.10.sup.-6 .degree. C., a dielectric constant of about 3.8 at X-Band frequencies, a loss tangent of about 0.002 at X-Band frequencies, an average modulus of rupture greater than 10 Kpsi from room temperature to 1000.degree. C., and no crystalline phase present. The radome is made by an arc fusion process in which a quartz powder is placed within a graphite mold, then shaped by centrifugal force as the mold is rotated. An arc is then struck between electrodes within the mold cavity. The quartz powder fuses to form a dense silica radome which is removed from the mold after the fusion occurs.

Abstract: The invention relates to matching asymmetrical discontinuites in transmission lines to give low reflection coefficients (less than five percent) over a wide frequency band (corresponding to at least an octave in wavelength). A group of asymmetrical discontinuites, such as impedance steps in a waveguide, are matched by considering a reference plane whose position varies with frequency at which the reflection coefficient for waves transmitted in one direction is equal to that for waves transmitted in the opposite direction. Matching elements are then provided which have a reflection coefficient at the reference plane which is equal and opposite to the reflection coefficient of the discontinuities. Matching is less difficult if the distance between the steps is less than a quarter of a guide wavelength at all frequencies in the wide band mentioned above and such an arrangement is a "reduced quarterwave transformer".

Abstract: A radome-lens comprises a shell of dielectric material having an outer surface in the form of a small circle defined by a sphere and a plane intersecting the sphere, an opening at one end of the shell for reception of an antenna therein, the surface having a central axis which is normal to the plane and extends through the center of the sphere, and an inner surface having a spherical portion centered at a second center disposed along the axis adjacent the first mentioned center but spaced toward the outer surface. When so constructed, the invention functions as a radome in the sense that it houses and protects an antenna in the usual manner and also functions as a lens in the sense that it amplifies the scan angle of the antenna from an angle of less than 90.degree. to 90.degree. or more.

Abstract: A frequency independent constant beamwidth lens antenna concept is descri utilizing a point source to point focus nonspherical lens. The essential feature is that a twisted planar or hyperbolic paraboloidal phase or wave front is formed by the antenna which then in turn produces a frequency indepenent constant beamwidth beam in the far field of the antenna for radiation or reception of planar or nearly planar spherical waves. Moreover, the frequency independent constant beamwidth beam may be steered or scanned in azimuth without moving the lens antenna or a plurality of fixed beams in different directions may be formed simultaneously by the lens antenna.

Abstract: A dielectric antenna lens for planar wavefront/focal point conversion is configured of a series of concentric rings, each of which is contoured from a rear face to inclined termination edges that are delimited by the functional performance of the lens and which assist in the manufacture of the lens. In addition, the bottom edge of each ring, rather than terminate at a cylindrical side wall of an adjacent ring, terminates at a flattened region between itself and the adjacent ring. This flattened region effectively eliminates the acute angle wedge between rings and, together with the inclined termination edges of the rings, serves to enable the lens to be easily manufactured, as by injection molding, with the flattened land portions and inclined termination edges making possible removal of the lens from the injection mold.As a further aspect of the present invention there is provided a multiple wavelength conversion arrangement employing the dielectric lens in combination with a wavelength selective (e.g.

Abstract: In a multimode or multispectral electromagnetic detection system (11), a pair of rotatable scanning prisms (13' and 13"), each of said prisms comprising at least a pair of cooperative subprisms (13'a, 13'b, 13"a and 13"b), and the cooperative materials of the subprism being selected so as to ensure that electromagnetic radiation passing through the pair of rotatable prisms is equally deviated in a transverse direction.

Abstract: It is sometimes necessary to reduce the power of microwave transmissions, e.g. to avoid overloading a receiver or to reduce a transmitter's potential to cause interference. The invention reduces the power by inserting radiation absorbent material into the aperture of the antenna. In the preferred embodiment a membrane of absorbent plastics is stretched across the aperture of the dish reflector.

Abstract: A radar antenna arrangement with at least a pair of feeds, said arrangement including a corresponding at least a pair of lens elements, the element closest to said feeds effective for collimating the output beam of each of said feed, and the remaining ones of said elements each being associated with a different one of said feeds, whereby at least a pair of separate antenna beams are capble of projection toward a target region.

Abstract: An antenna assembly is provided for use in locating buried objects, particularly long thin objects such as pipes can be located, determining the position, and ascertaining the pipe direction by taking measurements from a single point, without mechanical movement of the antenna, and allowing a better suppression of spurious signals and reduction in false indications; which assembly has a plurality of antenna arms adapted and arranged to transmit and receive radiation into the ground and is characterized in that the arms have, on at least the surface nearest the ground, a cladding of a substantially lossless dielectric material, the relative permitivity of said dielectric being at least 3.5 and the thickness of said coating being at least .lambda..sub.d /20 where .lambda..sub.d is the wavelength of lowest frequency of the radiation to be transmitted from the antenna.