Abstract: A hydraulic pump (16) is driven by an induction motor (14) from a source of multiphase alternating current (10) of either fixed or variable frequency. The pressure is applied to a hydraulic load, which may vary, and change the pressure. A pressure sensor coupled to the pump produces pressure signals. The motor includes plural windings, typically three, associated with a number of poles. Each motor winding is driven by a different phase of controlled alternating current. A rectifier (46) coupled to the multiphase AC source generates direct current, which is filtered to minimize DC ripple voltage. A controllable multiphase inverter (54) is coupled to the rectifier and to the motor windings, for converting the direct voltage into multiphase alternating motor drive voltages of controllable amplitude and frequency.

Abstract: An array antenna especially adapted for spacecraft use includes a support frame made up of intersecting beams which form an "eggcrate" of square openings. A plurality of subarrays or radiating tiles are dimensioned to fit within the openings. Distortion of the support frame due to external forces, or due to expansion and contraction of the radiating tiles, is accommodated andor resisted by a four-point mounting arrangement for each tile. Each mounting is located on the center of the sides of the radiating tile, and the corresponding center of the side of the opening in which it fits. Each mounting consists of a thin, flexible mounting beam, extending parallel to the associated support beam, and fastened to the support beam at the ends of the mounting beam. The center of the side of the tile is fastened to the center of the flexible support beam, so expansion and contraction of the tile are compensated by bending of the flexible beam.

Abstract: A speech signal has its characteristics extracted and encoded (16), transmitted over a limited-data-rate path (18) and is decoded (20) and synthesized (22) at the receiving end. The characteristics include line spectral frequencies (LSF), pitch and jitter. The LSF are extracted by autoregression, and split-vector quantized (SVQ) in a single frame, and, in parallel, in blocks of two, three and four frames. The SVQ codes have equal length and are evaluated for distortion in conjunction with a threshold. The threshold is varied in such a manner as tend to select for transmission those codewords which maintain a constant data rate into a transmit buffer. A single-bit jitter bit, and encoded pitch value, are product coded with the selected LSF codeword, and all are transmitted over the data path (18) to the receiver. The receiver decodes the characteristics, and controls a pitch generated (1226) in response to the pitch value and a random pitch jitter in response to the jitter bit.

Abstract: A three-axis stabilized spacecraft includes a plurality of primary attitude control thrusters, the torque vectors of which lie in, or parallel to a primary plane. It also includes at least two more secondary attitude control thrusters, the torque vectors of which lie in a secondary plane which is not parallel to the primary plane. The control system produces attitude error signals, which are processed with a PID characteristic to produce impulse demand signals, all in known fashion. The impulse demand signals are transformed into an auxiliary coordinate system, in which two of the three auxiliary axes lie in the primary plane, and the third is orthogonal thereto. One of the secondary thrusters is selected, which has, along the third auxiliary axis, the largest torque magnitude and the same sign as the transformed impulse demand.

Abstract: An optical fiber cable includes one or more optical fibers surrounded by a dielectric longitudinal strength member such as an aramid braid. The cable penetrates a bulkhead at a connector which couples tensile forces acting on the strength member to the bulkhead, to prevent breakage of the fiber(s). The connector includes two mating annular conical members which surround the optical fibers, with the strength braid flared and extending between the mating conical surfaces. The two cones are forced together by a bulkhead connector with a first thread and a second connector with a mating thread, thereby captivating the strength member to the bulkhead to resist tension. Concentric or annular grooves are formed in at least one of the mating conical surfaces to aid in gripping the slippery strength member.

Abstract: A system for extracting a three-dimensional model of an object viewed in a selected scene, includes at least one camera for acquiring scene information, each from a different spatial-temporal aspect of the total scene. A digitizer converts the scene video and directional information to digital data, for at least temporary storage in a mass memory associated with a computer for data processing. An interactive display provides a means by which a human operator can view the stored scene information and select at least one scene object for which the computer will extract a 3D model, for subsequent use by a designated output device.

Abstract: A digital signal processor (24) includes a plurality of vector processors (212x), each of which is made up of a group of, for example, six signal processors (214x). Each signal processor includes Local 1 and Local 2 ports (201, 203), and the Local 1 port of one processor of a group is coupled by a path (218) to the Local 2 port of another processor, so the group forms a ring. Each signal processor (214) also includes a memory (234), an arithmetic processor (232), and a switcher (230) for making internal interconnections among the ports, and also includes a switcher control (364, 366). At least one of the signal processors (214) of each group is of a type including a further external port (206), by which data can be coupled by a path (105) to and from the group. The signal processors of each group can be interconnected for serial or parallel processing, all under the control of a group controller (216) associated with each vector processor.

Abstract: An image comparison arrangement uses an electronic computer to compare digitized fingerprint minutia maps of fingerprints of an unknown fingerprint set with corresponding maps of reference fingerprint sets which are stored in memory, in order to identify unknown fingerprints or to match fingerprints. The matching is performed by converting all the fingerprints to attributed relation graphs (ARGs) including nodes and branches, to which attributes are appended. For each fingerprint pair being compared, a distance matrix is generated, the elements of which are the similarities of stars. The highest-ranking star pair is selected as the starting point of a comparison tree, by which attempts are made to fill a match core with elements representing the matching stars. The comparison is of the various attributes of the nodes and branches of each star.

Abstract: Two opaque sheets made from the same electrically conductive polymer material have adjoining edges. Each sheet is carbon loaded, electrically conductive, opaque black polymer on a first broad side thereof. The sheets are joined along a seam region by means of an opaque, electrically conductive adhesive tape. The electrically conductive adhesive tape includes an elongated opaque sheet of electrically conductive polymer material of the same kind as that of the two opaque sheets which the tape joins. The opaque, electrically conductive adhesive tape also includes a layer of electrically conductive adhesive, which is connected to the electrically conductive polymer material. In a particular embodiment of the invention, the polymer material is polyimide. In a preferred embodiment, the two opaque sheets are thermal coverings for a spacecraft, and each includes a sheet of opaque polyimide, carbon loaded which is electrically conductive, on the exterior of the thermal coverings.

Abstract: A zero-momentum spacecraft's attitude is controlled by determining the torque required about a control axis to maintain the desired attitude, and, during each of recurrent control cycles, enabling a magnetic torquer if the torque demand exceeds a threshold. During each of the control cycles, thruster(s) are enabled to make up the difference between the torque demand and the estimated torque produced by the magnetic torquer. In determining the torque demand, the attitude rate signal is low-pass filtered to reduce noise, and the control loop bandwidth is maintained by totalling the estimated torque applied by the magnetic torquer and thrusters, integrating and high-pass filtering the estimated torque signals, and adding the filtered estimated torque with the filtered attitude rate signals to generate low-noise attitude rate signals. A three-axis system is described.

Abstract: A sigma-delta analog-to-digital converter (10) provides high loop gain for suppression of noise components by use of a regenerative feedback loop or resonator (50), which produces a comb resonance response 212), embedded in the main degenerative feedback loop (48). The main loop includes an ADC (32) which samples at a clock frequency, which in turn defines a Nyquist frequency. The main loop also includes a DAC (38) which has a transfer function (42), which is equalized by a filter (44). The resonator (50) includes a low-pass filter (52) which matches the equalized main loop transfer function, a DC block (56), and a null filter (54) which nulls the resonator gain at the comb peak which lies above the Nyquist frequency. The open-loop transfer function of the regenerative loop (50) is set to unity gain and 0.degree..+-.N 360.degree. phase at the frequency of the analog input signal. A multipole embodiment (510) has multiple regenerative loops (55o) which produce multipole noise rejection (642).

Abstract: A spacecraft is controlled by a composite attitude signal including two components with different passbands. In one embodiment, a spacecraft attitude control system includes an attitude sensor and a controller which provides a time derivative function. High frequency noise components of the sensed attitude signal are enhanced by the derivative, and tend to cause attitude jitter or excess power consumption. The jitter is reduced by low pass filtration of the sensor signal, but this undesirably reduces the high frequency response of the attitude sensor. The high frequency response is restored by high pass filter coupled to a reaction or momentum wheel tachometer, which produces a signal representative of the high frequency components of the body rate. A summing circuit couples together the filtered attitude sensor signals with the high frequency components of the wheel speed signal to produce a relatively noise free broadband body rate signal.

Abstract: An antenna array for use in space includes an optical solar reflector (OSR)-like structure (310, 510), with sheet of transparent dielectric material (320, 520) and a metallic mirror (322, 522) formed on the sheet. In order to allow the individual antenna elements to radiate electromagnetic energy, the metallic mirror contains apertures (330, 530) which, in one embodiment, define the antenna elements, and which, in another embodiment, are registered with the antenna elements of the array. Where the mirror exists, insolation is reflected, and the heat gain from insolation is minimized. At the locations of the apertures in the mirror, insolation passes through the OSR-like structure, which may tend to increase the temperature of the structure. According to the invention, the apertures are covered with a thin layer (370, 570) of semiconductor material such as germanium or silicon, which does not affect the electromagnetic energy flow.

Abstract: A radar system which uses an active phased-array antenna achieves improved clutter improvement factor (CIF) by powering the various transmit-receive (TR) modules of the antenna with direct voltage (DC) derived from a plurality of phases of the power-line alternating current (AC). Each TR module receives power which originates with one phase of the source AC. The phases are selected so that the modulation of the radio-frequency (RF) signals by each TR module tends to cancel in the summed signal from the array antenna.

Abstract: A bidirectional power converter array has overall voltage feedback, an error signal generator, and plural bidirectional power converter modules. Each module of the array includes a series inductor and local feedback based upon the inductor current. Each module also has a resistive current sensor, providing wideband local feedback. A low-pass filter is coupled to the current sensing resistor to reduce switching noise. The low-pass filter also reduces the bandwidth of the local feedback signal, so interactions with the overall feedback occur, which may result in instability. A winding transformer-coupled to the series inductor generates AC signal representing high-frequency components of the inductor current, relatively free of switching noise. The AC current sample is added to the low-frequency components derived from the resistor and low-pass filter, to form a low-noise local feedback signal, with sufficient bandwidth to reduce unwanted interactions with the overall system feedback.

Abstract: Monopulse radar operation is improved by nulling a single mainlobe jammer and multiple sidelobe jammers while maintaining the angle measurement accuracy of the monopulse ratio. A sidelobe jammer cancelling adaptive array is cascaded with a mainlobe jammer canceller, imposing a mainlobe maintenance technique or constrained adaptation during the sidelobe jammer cancellation process so that results of the sidelobe jammer cancellation process do not distort the subsequent mainlobe jammer cancellation process. The sidelobe jammers and the mainlobe jammer are thus cancelled sequentially in separate processes.

Abstract: A transducer array according to the invention includes forty-two acoustic transducers for use in a fluid medium, with each of the transducers having maximum lateral dimensions of less than one acoustic wavelength in the medium, whereby the transducers themselves tend to radiate isotropically. The elements of the array are located at the vertices of an regular geodesic two-frequency icosahedron. The transducer array also includes a driver or a receiver, or both, and arrangements for coupling them to the array elements. A switching circuit can couple the array elements alternately to the driver or receiver, depending upon the operating mode. A conventional delay controller is coupled to the acoustic transducers, for controlling an acoustic beam formed by the array. In a particular embodiment of the invention, the array is operated at frequencies selected so that the inter-transducer spacing of any two mutually adjacent transducers does not exceed 2.lambda./3, and is not less than .lambda./3.

Abstract: A phased-array antenna (18) for use with a frequency-hopping transmitter (16) includes a plurality of elemental antennas (210), each associated with a phase-shifter (212) which is controlled (20) to form a beam (216) in the desired direction at a base frequency. The antenna elements (210, 212) are formed into subarrays (408t, 408b) each of which is fed from a common port (310). A further phase-shifter (312) is associated with each subarray, for imposing a phase shift on a group of elements of the overall array. The further phase-shifters are controlled when the frequency of the transmitter is away from the base frequency, to cause a stepwise-continuous correction phase across the array, which maintains the desired beam direction.

Abstract: A spacecraft (10) includes and attitude sensor (16) for generating sensed attitude signals. A controllable drive arrangement (238) is coupled to a reaction wheel (46), for driving it in response to speed error signals. The drive results in changes in reaction wheel speed. The spacecraft has a digital speed sensor (248) coupled to the reaction wheel, for generating quantized speed signals. A reaction wheel speed error signal generator (234) produces speed error signals in response to the difference between the attitude command and the sensed attitude signals, corrected by signals responsive to the speed of the reaction wheel, whereby at low reaction wheel speeds, the quantization causes attitude errors.

Abstract: A monopulse signal processor provides target monopulse ratios and thus target angles having an improved accuracy in those situations where a low signal-to-noise ratio subsists and the monopulse ratio is derived from a sequence of pulses. The monopulse ratio value is determined by: ##EQU1## and .SIGMA..sub.Ii is the in-phase component of the sum signal for the i.sup.th pulse, .SIGMA..sub.Qi is the quadrature component of the sum signal for the i.sup.th pulse, .DELTA..sub.Ii is the in-phase component of the difference signal for the i.sup.th pulse, and .DELTA..sub..OMEGA.i is the quadrature component of the difference signal for the i.sup.th pulse.