Abstract: A distortion generator uses the source-to-drain conductive path of a FET as the nonlinear element, in either a reflective or transmissive mode. In the reflective mode, the signal is applied across the source-to-drain conductive path, and in the transmissive mode the source-to-drain conductive path is in series with the transmission path. The FET may be biased, and the gate impedance to reference potential aids in selecting the nonlinearity characteristic. Reflective embodiments of a predistortion equalizer include a circulator version and a 3 dB hybrid splitter version. Transmissive embodiments include a direct series embodiment, and another with a 3 dB splitter and a separator combiner. Limiter and log-amp uses are described.

Abstract: A high efficiency, regulated DC supply combines the rectifying and a series regulating elements into one device such as a MOS FET which is gated "on" or "off" by the polarity of an AC voltage from a transformer winding. During the "on" state of the MOS FET a feedback network varies the MOS FET gate voltage as necessary to provide regulation of the DC output voltage during the "on" period.

Abstract: A pipeline Fast Fourier Transform arrangement includes a cascade of four Butterfly Arithmetic Units (BAU). Weighting and control signals are coupled to each BAU in the cascade. A multiplexed memory arrangement operated in a "ping-pong" manner stores four-stage partial FFT signal as it is generated, and returns it to the first BAU in the cascade for subsequent passes to generate multiple-stage FFT signals. Each BAU includes local memories cyclically fed and addressed to generate temporal offsets, which differ among the processors of the cascade.

Abstract: An attitude control loop for a spacecraft uses a proportional-integral-derivative (PID) controller for control about an axis. The spacecraft body has at least a primary mechanical resonance. The attitude sensors are collocated, or both on the rigid portion of the spacecraft. The flexure attributable to the resonance may result in instability of the system. A compensator for the control loop has an amplitude response which includes a component which rolls off beginning at frequencies below the resonance, and which also includes a component having a notch at a notch frequency somewhat below the resonant frequency. The phase response of the compensator tends toward zero at low frequencies, and tends toward -180.degree. as frequency increases toward the notch frequency. At frequencies above the notch frequency, the phase decreases from +180.degree., becoming more negative, and tending toward -90.degree. at frequencies far above the resonance frequency.

Abstract: A satellite communication system includes first, second and third electromagnetic radiators, the first and second of which are a contiguous pair, and the second and third of which are also contiguous. Two channels of information are each modulated onto carriers at the same frequency by means of mutually independent modulations. The modulations may be by orthogonal pseudorandom codes. The first channel is applied to the first and second radiators, and the second channel is applied to the second and third radiators. The first and second radiators form a beam which if decoded for the first modulation is independent to that formed by the second and third radiators. Consequently, the feed apertures overlap in a manner which provides a more constant field intensity in each beam, and which saves size and weight by comparison with a single radiator of corresponding aperture for each channel.

Abstract: A satellite communication system particularly suited for trans-Atlantic communications is provided wherein a communications satellite is placed in geosynchronous orbit somewhere between Western European continent and Eastern American continent. The satellite includes an antenna adapted for orthogonal linear polarization and the antenna elements oriented at an acute angle with respect to orbit normal to result in polarization arrival angles as close to local vertical and horizontal as possible at the earth stations in the high rain rate regions of southeastern United States and Mediterranian region in Europe.

Abstract: A method for making a transition between a spin-stabilized spacecraft operating mode and a 3-axis stabilized mode includes the step of determining the orientation of the spin axis. A reference object detector such as a sun sensor produces a pulse as it crosses the reference, thereby completely specifying the attitude of the spinning spacecraft at that instant. Angular rate information is used to update the attitude information while a feedback system controls torques for slowing the spin and for assuming the desired attitude.

Abstract: A reaction-wheel stabilized spacecraft reduces attitude errors at wheel reversals by application of a dither component to the wheel torque command signal.

Abstract: A monopulse antenna array arrangement includes a transmit-receive processor (TR Proc) associated with each antenna element. Each TR Proc has a port associated with the radiating element and at least two further ports, one for a sum beamformer and another for a difference beamformer. Within each TR Proc, a switching arrangement allows transmitter signal to flow through a phase shifter and transmit amp during transmission, and allows received signal to flow through a low-noise amp and the same phase shifter on reception. Each TR Proc includes a coupling arrangement with a second phase shifter and a second output port, adapted to be coupled to a difference beamformer during reception.

Abstract: A predistortion equalizer for a power amplifier includes a linear channel and a nonlinear channel. A phase shifter is associated with the linear channel and an attenuator is associated with the nonlinear channel. A resistive power divider divides the received signal which is to be predistorted and divides it into two parts, each of which is applied to one of the channels. The two parts may be equal in magnitude. The linear and nonlinear signals at the outputs of the linear and nonlinear channels, respectively, are combined out-of-phase in a resistive combiner to produce a predistorted signal for appication to a power amplifier. The resistive combiner and divider maximize bandwidth.

Abstract: A beam steering arrangement includes at least one lens array in which the lenses of the array are spaced at the source spacing, and the array is translated perpendicular to the beams to achieve scanning. Beam-to-beam piston phase differences result in grating lobes, with the result that the steered beam occurs as grating lobes only at discrete angles. An array of phase shifters registered with the lens array is controlled to correct the piston phase difference, thereby providing continuous scanning. In a particular embodiment of the invention the sources of the source array produce collimated beams, and a second lens array is interposed in the beam path. The efficiency of the array is improved by translating both lens arrays rather than one.

Abstract: A translucent support, which may be the support surface of an article conveyor, supports objects, locations or dimensions of which are to be determined. A point light source or light sources severally illuminate the surface and object thereupon. An imaging apparatus located below the translucent surface generates signals representing the images of the illuminated translucent surface and the shadows generated by the object thereon. The signals for two or more illumination conditions are processed to determine the locations of at least portions of the object. A particular avatar of the invention uses a conveyor with translucent web.

Abstract: A compact, liquid cooled, ferrite phase shifter is capable of handling high power microwave signals without thermally stressing the ferrite core. The ferrite core is mounted on spacers inside of a hermetically sealed wave guide filled with a thermally conducting fluid. Heat transfer from the core to the housing is symmetrical thereby eliminating or minimizing thermal bending stresses on the phase shifter. Heat from the core is also coupled through the fluid to the phase shifter window for deicing the window.

Abstract: A Leadless Chip Carrier (LCC) is mounted on a circuit board on elongated solder posts to provide clearance between the LCC and the board. The process for producing solder posts involves the deposition of a temporary stencil surrounding the conductive pads on the board. The removable stencil around the pads provides support for molten solder during reflow and prevents the chip carrier from compressing the molten solder thereby insuring desirable spacing between the chip carrier and the board.

Abstract: A hollow waveguide includes a conductive peripheral wall arrangement centered on a longitudinal axis. The waveguide is short-circuited at a first transverse plane. A center conductor is connected to the short-circuit and extends along the longitudinal axis to an abrupt open circuit termination at a second transverse plane. The arrangement is fed at a location between the first and second transverse planes to produce both a fundamental waveguide mode and a center-conductor coupled mode. The fundamental mode has an amplitude taper in the horizontal direction but not in the vertical direction. At the abrupt termination, a higher-order waveguide mode is generated which, when phase-shifted by 180.degree., provides an amplitude taper in a vertical direction. A radiating aperture located near the 180.degree. phase shift point produces a radiation pattern which is similar in both the verticla and horizontal planes.

Abstract: A fuel or fluid level measurement arrangement for a spacecraft includes one or more electromagnetic transmission lines extending into the reservoir. The presence of fuel adjacent the transmission line changes the dielectric constant or loss characteristics of the transmission line(s) in a measurable manner. In one embodiment, strip transmission lines extend parallel to the fluid surface at various degrees of ullage, and the fuel level can be established to within the spacing between the transmission lines.

Abstract: A compound imager consists of two or more individual chips, each with at least one line array of sensors thereupon. Each chip has a glass support plate attached to the side from which light reaches the line arrays. The chips are butted together end-to-end to make large line arrays of sensors. Because of imperfections in cutting, the butted surfaces define a gap. Light entering in the region of the gap is either lost or falls on an individual imager other than the one for which it is intended. This results in vignetting and/or crosstalk near the butted region. The gap is filled with an epoxy resin or other similar material which, when hardened, has an index of referaction near that of the glass support plate.

Abstract: A feedforward predistortion equalizer includes a first loop with a signal divider for dividing signals into first and second portions, and a distortion generator for distorting the second signal. The first loop is completed by a signal combiner which combines the undistorted first signal and the distorted second signal. The phase and amplitude of the signals in the loop are controlled so that the linear or carrier signal component is cancelled, leaving at the output of the first combiner only the distortion component of the distorted signal. A second loop includes phase and amplitude controls for combining the pure distortion and undistorted signals to produce the desired predistorted signals. In a particular embodiment, the phase and amplitude controls of the first loop are automatically adjusted for a null.

Abstract: A display changes the color of reflected light in response to the value of electrical potential applied to individual pixels of the display. Each pixel includes an array of light reflectors mounted on a corresponding array of electrostrictive elements. In the absence of energization, all the light reflector lie on a common plane and reflect light of all colors. The electrostrictive elements of each pixel in one embodiment are connected to be driven in common by a single potential. Each electrostrictive element of the array of each pixel has an effective length which differs from that of the adjoining elements so that the common voltage results in a differential expansion or contraction. The differential movement results in a separation between adjacent reflectors. When the separation is .lambda./4 at the wavelength of a color of light, destructive interference cancels that color, whereby physiological effects change the apparent color of the reflected light.

Abstract: A deployable crossed log periodic dipole array is made up of a plurality of bays spaced along a feed transmission line arrangement. Each bay includes a support centered on the array axis. Each bay also includes as antenna elements four long, straight, flat or slightly bowed springs or spring-like tape elements, each fastened at one end to a transmission line conductor. A retainer associated with each bay is rotatable about the cylindrical support and engages the spring elements, so that rotation of the retainer winds the spring elements against the spring resistance and stores energy therein. A locking arrangement simultaneously engages or disengages all the retainers. Simultaneous unlocking of the retainers allows the springs of all the bays to rotate the retainers and to unwind. As the springs unwind, they deploy. The transmission line arrangement includes two open two-wire transmission lines on a common axis. To reduce torques during deployment, each bay contrarotates relative to an adjacent bay.