Abstract: A cube-corner retroreflector for laser telemetry corrects speed aberration .delta. and has three substantially orthogonal mirror surfaces defining three substantially orthogonal edges converging at an apex. Each edge is associated with the surface substantially orthogonal to it. The shape of each surface is at least approximately that of a portion of a cone whose axis is coincident with the associated edge. The generatrices of this portion of a cone have a non-null average generatrix slope relative to a plane perpendicular to the axis of the portion. The average .alpha..sub.0 of the average slopes of the surfaces at least approximately satisfies the equation:.alpha..sub.0 .about.0.2.delta./kwhere k is a predetermined parameter dependent on the number, the geometry and the refractive index or indices or the media constituting the interior volume of the retroreflector.

Abstract: There is disclosed herein a system for reflecting electromagnetic radiation emanating from a doppler-based radar source toward the source whereby at least a portion of the difference between the emanating and reflected signal is continuously varied between preselected limits by causing the reflector to oscillate along the beam axis. The reflector is moved between approximately 0.001 and 0.250 inches and at a frequency mix ranging between about 2,000 Hz and 15,000 Hz. The reflector is mounted to a reciprocating system which is provided to drive the reflector.

Abstract: A coating composition for the attenuation of the reflection electromagnetic radiation and particularly electromagnetic radiation have a wavelength of greater than 800 nm including the near infrared is described. The composition comprises a chromophore capable of absorbing up to about 95% of the electromagnetic radiation having a wavelength greater than 800 nm. Optionally, the composition may comprise microbeads that serve the purpose of also scattering the electromagnetic radiation.

Abstract: A technique for determining the spin history of kinetic energy penetrator projectiles. The method employs a special dihedral plug fitting in the rear (tracer well) of the penetrator projectile that produces a modulation of the tracking radar's signal. This signal is recorded and analyzed to yield the rotation rate of the projectile as it travels down range.

Abstract: A system (10) for friend-or-foe identification (IFF) comprises an interrogator unit (18) carried on a first platform (T1) for generating and transmitting a laser beam. A control unit (22) selectively directs the transmitted laser beam toward a second platform (T2). A coding/decoding unit (28) encodes an IFF interrogator message with which a portion of the transmitted laser beam is modulated. A laser reflector (30) carried on the second platform receives the coded laser beam. The reflector is a normally passive reflector which is activated by receipt of the transmitted laser beam. The reflector responds to the IFF message contained in the received laser beam by modulating the unmodulated portion of the transmitted laser beam. This newly modulated portion of the laser beam is reflected back toward the first platform. The coding/encoding unit decodes on the first platform receives and the response, and determines if it corresponds to a predetermined response which identifies the second platform as a "friend".

Abstract: An apparatus for use, for example, as a runway radar signal reflector, for reflecting incoming radar signals, which includes a reflector for reflecting the radar signals, a chamber through which the incoming signals pass on the way to the reflector, and a mechanism for periodically creating a plasma in the chamber so as to prevent the incoming radar signals from being reflected.

Abstract: A lens such as a Luneberg lens is used in a retro-reflector having a plurality of reflector elements formed in a mosaic covering a predetermined portion of the lens. Each of the reflector elements may be individually controlled independently of the others; in this way, an interrogation source whose direction can be determined can have its interrogation signals reflected back only to it by having only one or a selected few of the reflector elements act as reflectors. Reflection in other directions may be suppressed by causing the other mosaic elements to act as absorbers. In addition, the reflectors can have their reflective or transmissive properties modulated so as to act as amplitude or phase modulators of the interrogation signal. In this way, information can be imparted to the reflected interrogation signal.

Abstract: This invention is directed to an expendable which includes an electronic circuit for introducing a simulated Doppler frequency shift. When dropped from an aircraft, the expendable is used to confuse hostile radar operations. In the past, the approach has been to use a high frequency electronic switch (PIN diode) and drive oscillator to change the impedance of the expendable antenna. This invention involves a simplification which combines the electronic switch and its drive oscillator into a single semiconductor component. By connecting a feedback circuit from the collector to the base of a high frequency transistor as well as to the two arms of the antenna, the antenna impedance is changed at the transistor oscillating frequency.

Abstract: The attenuation of electromagnetic waves by a transmission medium is detected or measured by directing a continuous periodic electromagnetic wave toward a reflector. The reflector is modulated to modulate the electromagnetic wave as it is reflected. The reflected wave is received and an output signal related monotonically to the power of the modulated reflected wave is detected. The output signal is then compared to the output signal which is or would be obtained under various other transmission conditions.

Abstract: Apparatus for detecting the position of a vessel in a broadcast image of the radar scan in a radar monitored area includes a television monitor for displaying a broadcast image of a radar scan of the area, and a controllable reflector for varying reflection of the radar waves impinging thereon from the monitoring radar to produce identifiable signal components in the broadcast image of the radar scan received on the television monitor. This controllable reflector may be actuated by the vessel operator to vary the reflection of the radar waves and produce variations in the broadcast image to enable the operator to identify the position of the vessel in the radar scan image appearing on the monitor. The monitoring installation includes a monitoring radar transmitter/receiver, and a television transmitter televising an image of the radar scan. Desirably, it includes a scan converter which receives the signals in polar coordinate form and provides rectangular raster signals with X and Y coordinates.

Abstract: A tunable high-frequency device using a superconductive thin layer with a thickness smaller than the thickness of penetration of a magnetic field is positioned on a dielectric layer. Also included is a means for varying the density of the Cooper pairs of the superconductive thin layer.

Abstract: An identification friend-or-foe system for vehicles wherein each vehicle is provided with a radiation transmitter and a receiver with a detector for detecting radiation transmitted by other vehicles. Each transmitter can transmit a first coded signal which can be detected by the receivers in other vehicles, the receivers providing an unblocking signal after the first coded signal is correctly identified. The unblocking signal clears a radiation transmission path in the vehicle, the path containing a reflector which reflects the received signal back to the source of the transmission. The reflector adds a further predetermined code to the signal reflected from the reflector with each vehicle having another detector for detecting a reflected signal and a device to identify the further predetermined code.

Abstract: An improved passive IFF system operating as a supplement to a conventional adar system including a coded variable delay system to produce like time-coded variable phase delayed identifying signal components indicative of cooperating or friendly objects and which overlap signals of other reflecting echo signals from the objects. The IFF system is provided with a retro-directive type antenna. The overlapping cooperating or friendly signal components and the corresponding other echo reflecting object signals are simultaneously detected at the radar system which is provided with a compensating or complementary phase delay means time coded in the same manner as the identifying IFF signal components. The identifying IFF signal components are thus produced in uniform phase and are summed up to provide a signal at the radar system whose magnitude is relatively large as compared to the combined corresponding echo reflecting signals which are in random-phase relationship.

Abstract: A radar reflecting target comprises a plurality of reflecting elements spread along at least one linear physical dimension of the target, the elements being differingly spaced in the direction normal to said dimension so that respective retro-reflections by the elements of radio frequency energy from a remote soucre on a line of sight at an angle to said dimension, have differing phases and tend to cancel each other out. The invetion may be applied to single or two dimensional surfaces on such vehicles as ships or aeroplanes.

Abstract: An adjustable focal length reflector for operation in space includes a membrane having a reflective surface. The membrane is subjected to incident radiation pressure. An assembly is located at the perimeter of the membrane to exert force on the membrane to counteract the incident radiation pressure in order to vary the focal length of the reflective surface. In a preferred embodiment the assembly includes an inflatable torus whose internal pressure is varied to vary the amount of force exerted on the membrane.

Abstract: An active radar stealth device mounted on a host platform for minimizing radar cross-section of the host platform. A coating which is essentially microwave transparent is attached to the surface of a host platform and is exposed to an incident microwave field. A plurality of detector/emitter pairs contained within the coating detect and actively cancel, respectively, the microwave field at each respective detector/emitter pair.

Abstract: A mechanical Doppler shifting device for a high frequency radiated beam comprises a rotating helical reflector having its axis of rotation parallel to the beam and a plane stationary mirror mounted parallel to the axis. The helix has a smooth reflective surface which is at a 45 degree slope with respect to the axis so that the distance to the surface from the source of the beam varies with the rotation of the helix. The beam is reflected from the helix to the plane stationary reflector and back upon itself to the source at a Doppler shifted frequency. Also disclosed is a system using 2 helical reflectors, the second being a mirror image of the first and being oppositely rotated synchronously therewith for reflecting the beam to a receiver spaced from the source of the beam.

Abstract: A reflector of an antenna in a radar system subject to jamming carries a multiplicity of localized phase shifters which are sequentially controlled by a processor to introduce certain phase modifications into incoming signals reflected toward an associated radiator. The processor, operating on branched-off portions of the incoming signals, compares the magnitudes of the signals received in the several operational states of each phase shifter and maintains that operational state for which the signal level is at a minimum. The comparisons may be carried out on signals received at the end of a signal-transmission cycle, lacking a useful component.

Abstract: A finely detailed defraction grating is applied to an object as an identifier or tag which is unambiguous, difficult to duplicate, or remove and transfer to another item, and can be read and compared with prior readings with relative ease. The exact pattern of the defraction grating is mapped by diffraction moire techniques and recorded for comparison with future readings of the same grating.

Abstract: An arrangement for modifying impressed radars signals with an internally generated signal to establish a misrepresentative return signal which is confusing as to actual range, size and position.

Abstract: A constant amplitude Doppler producing radar reflector for simulating a moving target. A plurality of dihedral reflectors having equal radar cross sections are rotated axially at equal rotational speeds. The dihedral reflectors are separated laterally and in the direction towards the illuminating radar by a distance which keeps the radar returns from the two reflectors in phase quadrature. With the radar cross sections of the reflectors being equal, the return signals to a linearly polarized radar maintains constant amplitude as the dihedral reflectors rotate.

Abstract: An airport landing system includes an airborne transmitter and receiver for transmitting RF energy at a first frequency and receiving RF energy at a second frequency. A stationary RF energy focusing means for focusing received RF energy. At least four receive/transmit modules and at least one RF source module. The RF source module for amplitude modulating and amplifying the received RF energy for retransmission by the receive/transmit modules. The receive/transmit modules having RF energy collector horns physically arranged with at least two vertically disposed horns and two horizontally disposed horns for transmitting at least four relatively high gain powered beams whose patterns cross over at their half power points with the crossover point defining the approach path.

Abstract: High magnetic permeability composites are obtained by incorporating ferrite fibers in the composites. The ferrite fibers consist of a polymer and particulate ferrite fill at a concentration above the percolation threshold for the ferrite fill in the polymer (typically greater than 30 volume percent). The aspect ratio and ferrite concentration of the fibers are selected to minimize demagnetization fields in the fibers. The fibers can be dispersed in low concentration in an unoriented fashion in the composites to impart high magnetic permeability to the composite. In other embodiments, the fibers are oriented in the composites to impart high magnetic permeability to the composite for incident radiation of a particular linear polarization.

Abstract: A radar system comprising an RF transmitter and receiver means for mounting in a moving carrier for transmitting RF energy and receiving RF energy returns and a non-rotating modulating radar reflector which has a lens means for focusing incident impinging RF energy onto a spot opposite the incident side and a plurality of solid state modulating radar reflectors positioned at the spot locations for selectively reflecting the RF energy and dissipating the RF energy for providing RF energy returns modulated with a lens identification code and frequencies for determining true ground speed, range, glide slope, and azimuth position.

Abstract: A ground speed determining radar system for take off roll and landings and roll out maneuvers has a ground based modulating radar reflector and a carrier based radar. The radar transmits microwave energy to the reflector where it is modulated by rotating spaced reflectors and returned to the radar receiver. The receiver is a heterodyne receiver having a log IF stage and a fast time control (FTC) circuit for attenuating clutter and an acquisition loop circuit, lock-on circuit and tracking loop circuit. The acquisition loop circuit includes a center, gate, modulation bandpass filter, switch, acquisition sweep generator and gate generator; the lock-on circuit adds a delay line and a good data indicator to the loop acquisition circuit, and the track loop circuit includes early/late gates, early/late gate low pass filters, subtractor, integrator, the switch and gate generator.

Abstract: The conventional way of achieving an identification, friend or foe (IFF) function for a moveable subject requires the subject to carry a transponder that emits a coded return when a radar pulse is received by its receiver. In the present invention, an IFF system is disclosed which departs from the conventional transponder method and employs no radio-frequency power source. Instead, it uses the scattering or reflecting properties of an antenna to modulate, in a distinctive manner, the radar return from a moveable subject. A binary sequence code generator modulates the impedance of a receiver antenna, with the reflected signal being detected and correlated with a synchronized code sequence at the radar.

Abstract: A radar target simulator apparatus and method especially useful with a pulse compression radar located in a remote, unattended, and unpowered, terrain. Provision for generating signals which will pass through moving target indication (MTI) and minimum velocity threshold circuits are included. Transmission of the detected simulated target data through narrow-band communications lines, such as telephone lines, is contemplated. The capability for minimum discernible signal and radar power output evaluations are also provided.

Abstract: A flat plate reflector at one station, responsive to ambient vibrations, is illuminated by a narrow beam of radio frequency waves transmitted from a second location, the transmitted waves being modulated in direct proportion to the ambient vibrations and reflected back to the second station for analysis.

Abstract: The invention concerns beacons associated to radars.It consists in modulating the re-emitted signal, in phase by the frequency of a vocal signal, and in amplitude by the envelope of this signal.It allows vocal transmission between such a signal and a Doppler radar.