Abstract: The present invention relates to a phased array antenna system which transmits a local oscillator signal in a scanable spotbeam from a first array of feed elements (12.sub.l -12.sub.m) via a reflector or lens (16) and a frequency diplexing means (18) to a second array of feed elements (20.sub.l -20.sub.n) disposed on the image plane of the first array of feed elements. A message signal in a second beam also impinging the frequency diplexing means from a separate direction is also received at the second array of feed elements. The message signal and the local oscillator signal concurrently received at each of the feed elements of the second array are mixed in individual mixers and the output of each mixer can be reradiated for transmission to a remote receiver or combined with the outputs of the other mixers for use by a local receiver.

Abstract: The present invention relates to a technique for enabling an antenna system to linearly scan over a wide angle of an orbital arc segment from a terrestrial ground station to access or track satellites within the segment. The wide angle linear scan capability is achieved by orienting the antenna system at the ground station relative to the local terrestrial coordinate system such that the axis normal to the aperture plane of the antenna system is at a predetermined angle and lies in a plane substantially parallel to the plane of the orbital arc segment. Then, by squinting the beam toward the orbital arc segment by applying a fixed linear phase taper to the antenna elements of a planar phased array along one axis of the array, linear scanning of the orbital arc segment is possible by, for example, varying the linear phase taper applied to antenna elements along another axis of the array.

Abstract: The present invention relates to a high speed optical switch and the use of such switches to form a time division demultiplexer. The optical switch comprises a length of linear material (12) including an outer surface on a portion of which is formed a layer of nonlinear material (11) to form a nonlinear interface (10) at the boundary of the two materials. An input data light beam (14) is propagated in the linear material with a predetermined intensity and angle of incidence on the nonlinear interface to, by itself, cause total reflection of the input beam. A control light beam (11) is also selectively energized and directed at the nonlinear interface with an intensity and angle of incidence to cause a portion of the input data beam to be formed into a self-focused channel or beam propagating in the nonlinear material. The self-focused beam can then be detected at an edge of the nonlinear material.

Abstract: The present invention relates to a dual frequency band, dual-mode feedhorn comprising three serially connected waveguide sections (20, 22, 24) and a separate discontinuity (21, 23) at each joint between waveguide sections. More particularly, the feedhorn comprises a first waveguide section (20) for supporting the TE.sub.11 mode in both frequency bands. A first discontinuity (21) symmetrically increases the first waveguide size for converting a portion of the TE.sub.11 mode in both frequency bands into the TM.sub.11 mode. The second waveguide section (22) connected to the first discontinuity comprises an aperture size for supporting the TE.sub.11 mode in both frequency bands but only the TM.sub.11 mode of the higher frequency band. A second discontinuity (23) symmetrically increases the size of the second waveguide for converting another portion of the TE.sub.11 mode in both frequency bands into the TM.sub.11 mode.

Abstract: The present invention relates to a rectangular corrugated waveguide or feedhorn wherein a plurality of adjacent grooves of a predetermined depth and cross-section are formed, preferably by numerical machining, in a major exposed surface of each of four plates of an electrically conductive material. The four plates are then secured together to form a rectangular corrugated passage therebetween where the ends of the line of grooves in one plate substantially meet and are aligned with the ends of corresponding grooves in another plate to form a solid line of electrically conductive material at the corners of the passage.

Abstract: The present invention relates to a feed arrangement for use with compact scanning beam antennas which comprises a linear phased array of small feed elements (10) which form an approximate line source that radiates a wedge-shaped cylindrical beam toward a subreflector (12) which is shaped to focus the wedge-shaped cylindrical beam to a point source which then produces a spherical wavefront. The spherical wavefront can then be focused by a main reflector (14) into linear scanning beams if desired. Multiple linear phased arrays of small feed elements can be disposed parallel to each other to form a multibeam feed arrangement for producing multiple fixed or scanning spot beams.

Abstract: A demultiplexer circuit which extracts from an incoming time division multiplexed digital bit stream any combination of PCM encoded words (in separate channels), or data bits irrespective of the rate of the latter or the position of the data bits in a given channel. The demultiplexer circuit includes a random access memory (12) (RAM) for storing information as to the channel(s) to be demultiplexed out of the incoming digital bit stream. A counter (13) operates in synchronism with the received bit stream and the output thereof serves to access the RAM to provide output signals indicative of the channel(s) carrying information for the subscriber station. These output signals are utilized to read the digital signals intended for said station into a shift register (16). A summing circuit (17, 18) is interconnected with the register so that conference calls are summed in real time. Before the next frame of digital signals, the contents of the register are transferred to a second shift register (21).

Abstract: The present invention relates to an antenna arrangement which uses an imaging reflector (10) combined with a small feed or horn (14) which is capable of launching or receiving a spherical wavefront (18) to obtain a nearly frequency independent field distribution over a large antenna aperture. The antenna arrangement comprises a parabolic main reflector (10) disposed confocally with one focal point of a subreflector means (12) and a feed (14) disposed with the apex of the spherical wavefront at the other focal point of the subreflector means and the aperture of the feed centered on the image of the main reflector. If the rim of the feed aperture corresponds to an image of the edge of the main reflector, spill-over is substantially eliminated. Generally, any feed arrangement comprising a feed and subreflector means which transforms a spherical wavefront from the feed into a spherical wavefront emanating from the focal point of the parabolic main reflector can be used.

Abstract: The present invention relates to a small hybrid mode feed for dual frequency band use. In the present feed, a helically wound wire structure (10) is bonded to the inner surface of a hollow conducting waveguide structure (12) by a layer (14) of low-loss dielectric material having a predetermined thickness to permit a first frequency band to propagate. Embedded in the dielectric layer between the helically wound wire structure and the inner wall of the waveguide is a periodic tuned grid structure (16) disposed at a predetermined depth from the helical wire structure to permit a second frequency band to propagate. The periodic tuned grid structure can comprise, for example, a Jerusalem Cross grid arrangement.

Abstract: The present invention relates to a low power, beam switchable, antenna comprising a focusing reflector (14), a plurality of feedhorns (10.sub.1 -10.sub.N) disposed on a surface (.SIGMA.) adjacent the focal surface of the focusing reflector, and an amplifying array (20, 24, 28) disposed in the aperture of the focusing reflector. A spherical wavefront launched by a feedhorn is reflected by the focusing reflector into a first planar wavefront which is intercepted by the amplifying array using a planar array of first feed elements (20.sub.1 -20.sub.X) disposed on a fourier transform surface (.SIGMA.') of the surface on which the feedhorns are disposed. The signal produced by each of the first feed elements associated with a first planar wavefront is separately amplified with an equal relative phase shift to the other associated intercepted signals and reradiated in a second planar wavefront by a planar array of second feed elements (28.sub.1 -28.sub.

Abstract: The present invention relates to phased array antenna arrangements which comprise a linear array of feed elements where the array has an aperture which is out at a bias angle along the minor axis of the array to produce a fixed linear phase taper along the minor axis by all elements. Then by linearly scanning the array along the major axis of the aperture of the array, a beam is scanned along an arc which can be made to correspond to an orbital arc segment around a celestial body and within the field of view of the antenna arrangement when the bias angle is properly chosen. The feed elements can comprise long feedhorns or horn antenna configurations which can be used in a separate array or disposed in an array on a conjugate plane of a main cylindrical reflector when used in multiple reflector phased array antenna arrangements.

Abstract: The present invention relates to an array phasing technique which normally provides directional spotbeams, and in the event of a failure mode of a phase shift controller for providing a wide area coverage beam. In an arrangement for practicing the present technique, each array feed element has disposed at its input a serial arrangement of a fixed value phase shifter (32) and a variable phase shifter (34). Each variable phase shifter has a separate control signal supplied to it by a phase shift controller (36). During normal operation the combined fixed value and variable phase shifters cause the array to radiate a flat wavefront in a predetermined direction, and in a failure mode of the phase shift controller the fixed phase shifters cause the array to radiate a diverging area coverage beam.

Abstract: Many prior art bistable optical devices require resonant optical cavities and are therefore limited in their operation due to the long lifetimes associated with their high-finesse cavities. A bistable optical device that does not use a resonant cavity is disclosed wherein a nonlinear medium whose index of refraction increases with increased light intensity is arranged to have input and output faces into which and out of which a laser beam having a nonuniform spatial profile can be propagated. A mirror having a predetermined area of reflectivity is positioned with respect to the output face of a nonlinear medium so as to reflect only the light energy that propagates in an area at the output face that is approximately equal to the area which the beam presents at this face when the beam is propagating at a critical power level, that is, when the beam is self-trapped.

Abstract: In its most general form, the present invention may be employed to simultaneously transmit information, either digital or analog, from two separate and distinct sources, denoted A and B, where the information from at least one of the sources, for example, A, possesses some known statistical properties of coherence. The less coherent information from, for example, source B, is used to generate a set of scrambling key sequences, where each separate scrambling key sequence is associated with a unique segment of information from source B. The key sequences are used to scramble the information from source A, and the scrambled information is produced as the output of the transmitter. In one form, the information from source A could be an analog signal (x(t)) and the information from source B could be a digital data sequence ({d.sub.k }) which is capable of transmitting n data bits per every N samples of the analog signal from source A.

Abstract: An auto-ionization pumped anti-Stokes Raman laser is disclosed which is capable of creating a population inversion between the ground state and a metastable state of an ionic lasing material. The lasing material is first pumped above a metastable energy level, where it subsequently falls via auto-ionization back to the metastable level. A second laser pump is employed to move the population from the metastable state to a region near an intermediate state of the lasing material. The population subsequently falls back to the initial ground ionic state, thereby creating the anti-Stokes Raman emission.

Abstract: Tunable laser radiation is obtained by pumping a wedge-shaped ultra-short laser cavity with picosecond excitation pulses. Continuous tuning of the laser is achieved by translating either the wedge-shaped laser cavity or the excitation pulses so that different volumes of the laser material are exposed to the excitation pulses. In one embodiment utilizing picosecond laser excitation pulses the wedge-shaped laser cavity is a slightly wedged film of GaAs coated on both sides with dielectric mirrors.

Abstract: The present invention relates to a secure communication system for analog signals which preserves the bandwidth of the original message signal by employing scrambling, or masking, techniques in the frequency domain instead of the time domain. At the transmitting end, the message signal x.sub.a (t) is sequentially passed through a Fourier transform processor (12) and a scrambling arrangement (14) before being masked to form a secure Fourier transform sequence X.sub.s (n). The secure message signal x.sub.s (t) is formed by passing the secure sequence X.sub.s (n) through an inverse Fourier transform processor (16) which produces a secure signal x.sub.s (t) comprising the same bandwidth as the original message signal x.sub.a (t). At the receiving end, the secure signal x.sub.

Abstract: The present invention relates to a decoder for use in a spread spectrum radio receiver which is capable of directly demodulating an L-length frequency-hopped, Q-level frequency shift keyed radio-frequency received signal into a baseband signal wherein a desired user's message signal is decoded into a sequence of tone bursts at a fixed frequency over each L-length sequence. Spectral analysis is performed on the resultant baseband signal either during each chip interval or once at the end of each L-length sequence to permit subsequent detection of a desired user's correct received message signal.

Abstract: The present invention comprises an apparatus which provides a combination of excitation pulses or a signle shaped excitation pulse to a plasma-recombination laser which both creates the plasma and controls the electron-ion collisional recombination rate therein. The application of the single shaped excitation pulse or combination of excitation pulses keeps the electron temperature of the plasma at a temperature unfavorable to recombination until the electron density has fallen into the optimum range for laser action. The termination of the excitation pulse or pulses results in immediate laser action having power at least several orders of magnitude over that achieved in the prior art.

Abstract: The present invention relates to a phased array antenna system which, in the transmission mode, forms a directional planar wavefront (20) including a signal at a first frequency at a first array (18.sub.1 -18.sub.m) which is a sub-multiple of the frequency to be ultimately transmitted. By sending the wavefront through a lens or reflector, an image of the first array is formed on an image plane. A second array (26.sub.1 -26.sub.n) disposed at the image plane intercepts the wavefront and the received signal's frequency and phase is then harmonically multiplied by a predetermined number to permit reradiation of the resultant signal by a third array (32.sub.1 -32.sub.n) in the same direction as the original wavefront. The second and third arrays include corresponding elements and configurations with more elements than the first array. In the receive mode, the sequence is complementary to the transmit mode.