Abstract: Electromagnetic and optical shields, controllers, and reflectors comprising chiral materials. Electromagnetic and optical controllers and layers provided in accordance with this invention comprise chiral materials wherein reflection, scattering, absorption and shielding properties can be tailored over specified frequency regime. Layered structures have a variety of potential applications in radar cross section management, radar absorbers for low observables and other applications, radomes, antennae, and radio wave, microwave and millimeter wave chambers. Likewise, these structures have many applications to electronic devices, integrated optics, and optical components and systems, as well as in their radio wave, microwave, and millimeter wave counterparts.

Abstract: The invention is a pylon for supporting a model above a ground plane for radar cross-section testing using a radar providing a specific frequency range and power distribution above the ground plane. In detail, the pylon comprises a column made of a low dielectric constant foam material having a base end for mounting on the ground plane, a model mounting top end and a generally circular cross-section. The column has an abrupt change in diameter at a point between the ends forming a step and dividing the column into upper and lower tapered portions with each of the portions having a specific diameter range. The step is located at a point on the column such that the power is evenly split between the upper and lower portions and the specific diameter ranges of the portions are selected to maintain a 180-degree phase change in the return signal from each of the portions reducing the RCS of the pylon.

Abstract: An electromagnetic absorbing element is comprised of an elongated rectangular body of dielectric material having a bottom portion attachable to an inner wall of an electromagnetically dark room, and peripheral elongated faces extending vertically from the bottom portion such that a set of the absorbing elements can be arranged in rows-and-columns on the wall. An electroconductive ink film is formed on the peripheral faces of body and has a gradually changing surface resistivity decreasing exponentially lengthwise of the peripheral face toward the bottom portion. The incident electromagnetic wave normal to the wall provided with the rows-and-columns of absorbing elements is absorbed by a lattice of the electroconductive films during the travel along the electroconductive films.

Abstract: An electromagnetic radiation absorber is formed by dispersing into a dielectric binder acicular magnetic metallic filaments with an average length of about 10 micron or less, diameters of 0.1 micron or more, and aspect (length/diameter) ratios between 10:1 and 50:1. Preferably the average length is about 5 micron, the aspect ratios are between 10:1 and 25:1, and the dielectric binder is polymeric. The volume fraction of the filaments may be lower than 35% of the total and still provide satisfactory absorption. An absorbing paint is formed by dissolving the absorber in a base liquid. The absorber or absorbing paint may be applied to a conductive surface, such as a metallic wire, plate or foil. Impedance matching materials are preferred but not required.

Abstract: For reduction in occupation space without sacrifice of the responsible broad bandwidth, an electromagnetic wave absorber for electromagnetic waves is provided with an absorbing sheet formed of a non-woven fabric containing conductive fibers mixed with insulative fibers, and each of the conductive fibers is selected from the group consisting of a metal fiber or a resin fiber coated with a conductive material.

Abstract: The present disclosure describes a protective tarpaulin which protects military targets from detection and destruction by multiple weapon systems. The tarpaulin comprises a thermal protective sheet situated at its bottom surface in contact with the target it covers. A multi-cell honeycomb structure is disposed above and separated from the thermal protective sheet by a plurality of stiffeners. The tarpaulin also includes a temperature control means, in communication with an air gap defined by the space between the multi-cell honeycomb structure and the thermal protective sheet.

Abstract: A canopy screening an object, especially its thermally emitted waves and/or against hf electromagnetic waves in the microwave range, especially radar waves, has external textile sheets (1, 2) connected by a support fabric (13), i.e., a spacer, which forms a center space (10). At least one external surface, i.e. its filaments are provided with a coating (6, 7) which in part or in whole is reflecting in the thermal range and/or absorbing in the microwave range.

Abstract: An aircraft structure for the minimization of microwave energy reflection from the aircraft back to a receiver. The provision of structural configurations and materials operate to reduce microwave energy reflection toward its source or another receiver located at a level below the aircraft and laterally or forward thereof.

Abstract: In order to decrease the interfering reflection of radar radiation from building walls during radar surveillance on the ground, the outer walls are formed on their surfaces so that the reflected radar waves are subjected in part to a phase shift of one half wavelength with respect to each other. This results in a partial obliteration of the reflected waves. The reflecting surface of the outer wall comprises for that purpose of individual elements whose superficial extent is smaller than the surface irradiated by a radar impulse, and which are staggered in depth in such manner that adjoining surface elements are located at a distance from each other which is equal, for perpendicular incidence of the radar radiation, to one quarter wavelength of the radar radiation used.

Abstract: An inflatable target support system having a minimum radar cross section, a high mechanical strength, an ultra-high rigidity and a high load bearing capacity. The system comprises a thin, inflatable, stressed-skin membrane in the shape of a right cone which is sealed at its narrow end by a extremely rigid, plug and sealed at its wide end by a chamfer shaped base so as to provide exceptional rigidity to the system.

Abstract: An aircraft structure for the minimization of microwave energy reflection from the aircraft back to a receiver. The provision of structural configurations and materials operate to reduce microwave energy reflection toward its source or another receiver located at a level below the aircraft and laterally or forward thereof.

Abstract: An aircraft structure for the minimization of microwave energy reflection from the aircraft back to a receiver. The provision of structural configurations and materials operate to reduce microwave energy reflection toward its source or another receiver located at a level below the aircraft and laterally or forward thereof.

Abstract: The fiber composite for bearing structures for absorption of electromagnetic waves consists in its structure of at least three layers (2, 3, 4, 5, 6, 7, 8, 9) to be different in their electromagnetic material constants, whereby one or more fiber layers (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 24) are used for the layers (2 to 9). The fiber layers demonstrate alternately by layers a high or low electrical conductivity such that the electromagnetic material constants of the layers (2 to 9) composed of the fiber layers (13 to 21 and 23, 24) and binder and the layer thicknesses are matched to one another such that the reflection attenuation is integrally maximized in a given frequency range.

Abstract: A pylon for supporting a test target in an anechoic chamber during a radar cross section measurement. The pylon includes an elongated support extending upwardly from a base to a tip on which the test target is mounted. The support inclines and curves in the direction of an interrogating radar signal, and its tip is smoothly faired to the test target. The tip is formed from a resilient, radar-absorbing material, and it is bent by internal actuating means to vary the angular orientation of the test target.

Abstract: A plurality of waveguide elements are arranged to form an electromagnetic wave absorbing lattice in opposed relation to the advancing wave surface of the incident electromagnetic wave. Each waveguide element has a front opening on the lattice receptive of a part of the incident electromagnetic wave, a rear end portion spaced rearwardly from the front opening, and an inner peripheral surface portion extending between the front opening and the rear end portion to define a cavity effective to wave-guide the received electromagnetic wave. The inner peripheral surface portion has a given electric resistivity to effect absorption of the received electromagnetic wave during the wave-guiding thereof without substantial reflection thereof.

Abstract: A radiowave absorber comprises a porous ceramic matrix combined with carbon, where the carbon is combined on its surface and interior particularly in an amount not exceeding 2.7% by weight. A process for manufacturing a radiowave absorber is also disclosed. At least one kind of ceramic material selected from natural minerals or clay minerals, and artificial ceramic materials, is fired with a pore- or skeleton-forming material which can be burned away, whereby a sintered porous ceramic matrix is prepared. The matrix is fired in a furnace containing a reducing atmosphere and having a uniform temperature, while a gas or mist of hydrocarbon compound is introduced into the furnace.

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: An improved radar range comprising a ground plane (22), support means (28) for supporting a target (26) a selected height above the ground plane, transmitting means (24) for directing for a selected period of time an electromagnetic wave at the target, means (30, 32) for increasing the time required for the portion of the electromagnetic wave reflected off the target toward the ground plane to return to the target, and receiving means (24) for receiving for a selected period of time the portion of the electromagnetic wave that is backscattered by the target. In a particular embodiment, the means for increasing the return time includes means for recessing the support means a selected distance below the ground plane by providing a diffraction ridge (30) a selected distance from the support means toward the transmitting means with the ridge sloping down to the selected distance below the ground plane.

Abstract: An absorber for radiation of frequency of the order of 1 THz is formed of a body of cured silicone-based elastomer containing an inert, powdered siliceous filler. Both the elastomer and the filler are electrically insulating and the surface of the absorber that is exposed to the radiation is preferably profiled to enhance absorption of the radiation. The profiling preferably takes the form of an array of sharp-pointed pyramids having rectangular or triangular bases. A method of moulding such absorbers is also disclosed.

Abstract: For effectively suppressing echo of an electromagnetic wave emitted from an electromagnetic device (24) disposed in a closed space (13) which is defined by a shielding wall (10), an electromagnetic anechoic chamber comprises an absorption member (28) disposed in the space. The wall has an inner surface which reflects the electromagnetic wave into the space as a reflected wave. The reflected wave is directed to a particular position in the space. The absorption member is located at the particular position. Preferably, the inner space is formed along a substantially ellipsoidal shape having a first and a second focus point (14, 16). The electromagnetic device and the absorption member are locsated at the first and the second focus points, respectively.

Abstract: An aircraft structure for the minimization of microwave energy reflection from the aircraft back to a receiver. The provision of structural configurations and materials operate to reduce microwave energy reflection toward its source or another receiver located at a level below the aircraft and laterally or forward thereof.

Abstract: A radio-frequency unechoic chamber (electric wave nonreflecting room) is disclosed. The radio-frequency unechoic chamber comprises radiowave reflectors which are provided on all inside of peripheral walls whose upper portion is open and a screen to cut off reflected waves which is arranged between an antenna and the mounting table of a test apparatus and which has a gap for allowing only direct waves from said antenna to pass.

Abstract: A test subject is mounted in front of a radar antenna for measurement of a radar cross-sectional signature of the test subject. The test subject is mounted on an electrically conductive rotator mounted coplanar with an electrically conductive shield, there being a clearance space between the rotator and the shield to allow for rotation of the rotator. An electrically conductive seal is disposed in a shelf of the front surface of the shield in the manner of a fairing to provide a smooth surface of the shield which covers the clearance space for minimizing reflections of radiation, and for deflecting any reflections of radiation from the antenna away from the antenna. A rotator rotates the platform, and a tilt mechanism tilts the shield for variation in elevation angle. The foregoing apparatus is mounted within an anechoic chamber.

Abstract: Device to shield against an electromagnetic field, consisting of a shielding film made of metal, in particular aluminum or metallized plastic which is provided with openings, the shielding film having an essentially hexagonal outline and being subdivided into six triangular fields by ridges connecting the corners to the center of the film and the openings consisting of slits which are parallel to the hexagon side of each triangular field and to each other and extend over the entire triangular field (FIG. 1).

Abstract: The present invention relates to a method for assembling a dummy aeroplane in which a latticework carcass is constructed from the components of an assembly kit and covered with a weatherproof drape. The inventive method is characterized by the sequence of steps in which the upper parts of the carcass, or shell, are assembled at a first level, whereafter the assembled upper part is raised to a second level with the aid of lifting devices and held at this level by the lifting devices while lower parts of the carcass are assembled. These steps are then repeated until the undercarriage of the dummy aeroplane has been fitted, whereafter the lifting devices are withdrawn so that the dummy rests on its wheels, all of this assembly work being carried out at a level suitable for the assembly personnel concerned.The invention also relates to an assembly kit for carrying out the method.

Abstract: This invention is a device for absorbing microwave-type radio signals from a radar sending unit. The above is accomplished by providing a transformer effect with a conductive material which is connected to a signal neutralizing gas such as that found in fluorescent light tubes.

Abstract: A microwave absorbing ablating material is used as the ablative covering between the transmitting and receiving antennas while a standard ablating material, allowing the transmission of signals, is placed about the antennas. This allows signals to be transmitted from and received by the object covered by RF absorbing ablating material while preventing the transmission of signals transversely through the material. The RF absorbing, ablating material is made by combining an RF absorbing material with an ablating material in sufficient quantities to absorb and dissipate any signals that may be exposed to the ablative material.

Abstract: A shield for a satellite earth station located in a dense radio frequency environment. The shield includes a satellite earth station antenna position in a pit. Surrounding the pit is a tear-shaped earthen berm. Positioned on top of the berm is a wall made of a series of modular precast concrete panels specially designed to reduce the diffraction of radio frequency interference over the top of the panels and to minimize the internal reflection of radio frequency interference. The panels each include an inner face of two sets of horizontal slats set at alternating angles. The two sets of slats are designed to attenuate and disperse radio frequency interference in the range of the satellite communication downlink and uplink frequencies. In addition, the present invention includes specially shaped grooves cast into the top face of the panels which attenuate radio frequency interference passing over the top of the wall.

Abstract: An aircraft decoy is made by assembling metal or plastic pipe or tubing into tubing fittings to form the shape of an actual aircraft. The tubing is marked with location identification markings. The decoy thus constructed is easily disassembled, stored, transported, or reassembled. The aircraft decoy is covered with an open weave fabric to minimize air resistance so that high winds will not move the decoy on the ground. The fabric is coated with paint to mimic not only the optical characteristics or signature of the actual aircraft, but also the infrared and radar signature of the actual aircraft. Metal particles can be added to paint to increase the infrared and radar signatures.