Abstract: The present invention relates to polarization grids for use in offset antenna arrangements, each of the grids comprising a plurality of nonparallel spaced-apart elements which are mounted between an offset curved focusing main reflector and an associated feedhorn in order to obtain linear polarization everywhere in the far field of the reflector. Exemplary types of grids in accordance with the present invention are (1) a family of hyperbolae on an arbitrary plane S, (2) projections of these hyperbolae on an arbitrary surface, and (3) a set of straight lines through a certain point F.sub.o.sup.' on plane S which set approximates the hyperbolae of type (1) by means of a tangent to each of the hyperbolae.

Abstract: The present invention relates to a small digital time-division switching arrangement capable of interfacing with a plurality of PCM communication lines on one side and a separate plurality of transmission channels on the other side. A first processor primarily tracks call progress by scanning signalling bits indicating on/off hook state changes and a second processor controls the action of a time slot interchanger which both assembles and disassembles channel data and telemetry messages and establishes and breaks down calls while connecting appropriate service circuits to the communication lines during the progress of a call. The processors are implemented with separate microprocessor chips and associated memory and the switching arrangement can simultaneously communicate with a variety of call originating circuits employing a wide variety of control signals.

Abstract: A data throttling arrangement is advantageously incorporated in a pulse width modulated (PWM) to pulse code modulated (PCM) signal converter for controlling the output rate of the PCM data stream. PWM data is converted to PCM data and stored in a memory. New PCM data is received and compared with the stored PCM data. The difference between the stored and the new PCM data is compared to a preselected threshold value. If the difference between the new and stored data is greater than the threshold value, the new PCM data is permitted to output; otherwise, the new data is disregarded as redundant or insignificant. Circuitry is provided to adjust the values of incoming PCM data by comparing it to predetermined zero offset values. Additional circuitry is provided to permit adjustment of the preselected threshold values in response to the rate of the PCM output data stream.

Abstract: The polarization properties of the field radiated from a polarization grid have been found to be similar to those in the aperture of an offset curved focusing reflector. Therefore, broadband cancellation of the polarization rotation in a large offset reflector is substantially accomplished in the present invention by the opposite prerotation of the incident feed radiation via a polarization grid. For maximum cancellation the polarization grid, having parallel spaced-apart elements, is disposed at an angle to a plane normal to the feed axis of the offset reflector which approximates one-half of the value of the angle between the feed axis and the offset reflector axis.

Abstract: A high speed apparatus for converting an analog signal to a digital signal is disclosed. The analog-to-digital converter phase modulates a predetermined carrier signal with the analog signal and this phase modulated signal is transmitted along separate parallel paths to a first and a second phase detector where the phase relationship between the phase modulated signal and each of a first and a second sample, respectively, of the carrier signal which differ in phase by substantially 90 degrees from each other is detected. The output signal of each detector is compared with a reference potential to generate a zero or a one dependent on the magnitude of the detector output relative to the reference potential. Subsequent bits of the digital output signal can be generated by frequency doubling both the phase modulated signal and the carrier signal as applied to the previous parallel path for conversion in a separate corresponding parallel path.

Abstract: The present invention relates to a multibeam, digitally modulated, time division switched communication system especially for use with a satellite repeater wherein separate up-link and down-link signals are transmitted between each of a plurality of ground station areas and the repeater using space diversity techniques. The frequency band of each up-link signal is split to include at least two frequency multiplexed channels, each channel being separated at the repeater and independently switched at baseband frequencies through a repeater switching network comprising at least two matrix switches for retransmission on the appropriate down-link signal.

Abstract: The present invention relates to two novel approaches for implementing an approximation of the Viterbi decoding algorithm using analog processing techniques which offer the potential for decoding at higher rates than currently achievable with digital processing decoders. The first approach employs at least one tapped delay means having a plurality of taps to enable the provision of the inverted and noninverted received analog channel waveform while path metric operations are performed by selectively switching between corresponding inverting and noninverting provisions of the at least one delay means according to the contents of a decision-directed digital memory. The second approach employs sample-and-hold circuits to store and update the path metrics based upon previous maximum-likelihood decisions.

Abstract: The present invention relates to a quasi-optical frequency multiplexer which permits the bidirectional conversion of at least two intermediate angularly-distinct planar wavefronts, where each distinct planar wavefront corresponds to the wavelength of a separate radio channel, into a single directional wavefront by the use of a blazed diffraction grating mounted at the aperture of an antenna. More particularly, a single directional planar wavefront, comprising the wavelengths of at least two radio channels, is diffracted out of the blazed diffraction grating into at least two angularly-distinct intermediate planar wavefronts corresponding to the at least two radio channels. By properly placing separate feedhorns at the precise location on the focal plane of the antenna where each angularly-distinct intermediate planar wavefront is focused, the radio channels can be separated, or alternately combined in the reverse manner.

Abstract: A launching and/or receiving network is disclosed capable of coupling radio signals in a first frequency band, e.g., 2 GHz into and/or out of an existing antenna system without perturbing the signals being transmitted in other frequency bands, e.g., 4, 6 and/or 11 GHz. The first frequency band signal is launched through an evanescent mode waveguide filter which is both coupled to the flared sidewall of a feedhorn through an H-plane, T-junction, and provides a very broad stopband for the signals in the other frequency bands being launched in the feedhorn. To minimize mode conversion for the signals in the other frequency bands, a dummy evanescent mode waveguide filter is connected at one end thereof to the feedhorn facing the first frequency band launching network and at the other end thereof to a matched load through a waveguide section.

Abstract: A directional optical waveguide coupler and power tap is disclosed for use with optical fibers or planar-form optical waveguides. Abutted to the end of a cladded optical transmission waveguide is a section of a second optical waveguide comprising a core surrounded by a cladding layer, the core having a smaller cross-sectional area than the core of the transmission waveguide. In the present arrangement, light energy propagating in the core of the second waveguide towards the transmission waveguide is coupled into the core of the transmission waveguide at the point of abuttment, whereas light energy propagating in the core of the transmission waveguide towards the second waveguide is coupled into both the core and cladding layer of the second waveguide at the point of abuttment.

Abstract: The present invention relates to thinned linear, planar and three-dimensional phased antenna array configurations which have the antenna or sensor elements positioned in a pseudorandom manner as prescribed by the equation based on difference sets. The present antenna array permit thinning factors well below one-half while retaining the sidelobe level characteristics of arrays with much higher thinning factors.

Abstract: The present invention relates to a method and apparatus for breaking optical fibers. The present method comprises the steps of: clamping an optical fiber at two spaced-apart peripheral areas on opposite sides of the area of intended break; heating the area of the intended break to at least the annealing temperature of the fiber; scoring the fiber along the line of intended break; and either bending and pulling or pulling the fiber apart to produce a break with a flat end surface. The heating step may also be advantageously employed to melt or evaporate a jacket surrounding the optical fiber adjacent to the area of intended break.

Abstract: The present invention relates to method and apparatus for fabricating multimode optical fiber waveguides having reduced modal dispersion as a result of deliberate enhancement of mode coupling in the waveguide. The axial alignment and/or the diameter of an optical fiber waveguide is varied by means of one or more modulated heat sources, such as, for example, a microflame jet or CO.sub.2 laser, directed against the fiber waveguide. By controlling the modulation of the heat source, the spatial distribution of the geometrical perturbation pattern can be controlled, thereby producing controlled mode coupling in the fiber waveguide.

Abstract: The present invention relates to the joining of a first glass member, such as an optical fiber, to a second member by means of solderable splices and terminations which additionally can form hermetic seals. To form the splice, termination or seal, the peripheral surface of the glass member is coated in the area of the intended joint between members with a thin adhering metallic layer. The coated glass member is properly positioned adjacent the second member and solder is flowed around the joint between the members. Where the second member is also formed of glass, a thin adhering metallic coating layer is similarly formed on the peripheral surface thereof in the area of the intended joint prior to solder being applied.

Abstract: The present invention relates to a linear phase modulator comprising two known Armstrong modulators connected in a balanced configuration to eliminate even-order nonlinearities in the output phase modulated signal. In addition, a preselected amount of in-phase carrier is added to the quadrature carrier normally added to the output of the suppressed-carrier modulator forming a part of each Armstrong modulator, the carriers being added to each modulator output, however, differing in phase from quadrature by equal and opposite amounts. By properly preselecting the amount of phase difference from quadrature of the added carriers, third-order nonlinearities can also be substantially eliminated after combining the outputs of the Armstrong modulators in a multiplier circuit.

Abstract: A receiver especially for use as a diversity combining receiver is adapted to recover a single signal from among a plurality of cochannel signals transmitted from a plurality of sources. When recovering signals from a plurality of sources, the various sources transmit signals having PSK modulation and having, in addition, pilot tag modulation uniquely associated with each source. The output from each of the diversity branches is combined and the combined output is mixed with the output signal generated by a free-running oscillator to produce a loop signal uniquely identified by one selected tag. The processing is arranged so that when this loop signal is mixed with each branch input, the resulting sideband product of the loop signal and the one received signal having the selected tag contains a distinctive cophasing phase angle but is stripped of its PSK information and tagging modulation.

Abstract: Directional optical waveguide couplers for use with planar-form optical waveguides or optical fiber waveguides are disclosed. In the coupler arrangements, light energy propagating in a direction of interest in the core of a cladded optical waveguide is first coupled into a selected region of the cladding by a mode coupling means and then coupled out of the selected cladding region by a branching optical waveguide or power tap for subsequent conversion to a representative electrical signal. The selected region of the cladding is isolated from spurious cladding modes by a pair of stripper-absorber means to ensure that the coupled out light energy is derived only from the core-guided modes propagating in the direction of interest.

Abstract: Method and apparatus are disclosed to permit an advantageous reduction in the cost and size of a compensating conventional or parallel feedforward amplifier. By adjusting the main power amplifier to generate a distortion component which is greater than normally generated by the main power amplifier in prior art conventional or parallel feedforward amplifiers, the amplification factor of the auxiliary power amplifier in the conventional feedforward amplifier or the amplification factor of the auxiliary power amplifier and the attenuation factor in the interstage coupler in the parallel feedforward amplifier can be relaxed.