Abstract: A DC—DC voltage converter has a controller, two switches, a transformer and two rectifying diodes. The transformer has a first winding, a second winding and a center tap. Input voltage is connected between the center tap and ground. An anode of each diode is connected to the outer ends of the two windings and the cathodes of the two diodes are connected together to provide a positive output with respect to ground. Each switch is connected between an outer end of one winding and ground. The controller generates control signals to turn the switches on and off for limited periods of time in phase opposition to alternately connect the outer ends of the first and second winding to ground to cause current to flow alternatively in one of the windings and induce a voltage in the other winding that is additive to the input voltage, thereby providing an output voltage greater than the input voltage.

Abstract: A DC-DC voltage converter comprises a controller, two switches, a transformer and two rectifying diodes. The transformer has a first winding, a second winding and a center tap. Input voltage in connected between the center tap and ground. An anode of each diode is connected to the outer ends of the two windings and the cathodes of the two diodes are connected together to provide a positive output with respect to ground. Each switch is connected between an outer end of one windings and ground. The controller generates control signals to turn the switches on and off for limited periods of time in phase opposition to alternately connect the outer ends of the first and second winding to ground to cause current to flow alternatively in one of the windings and induce a voltage in the other winding that is additive to the input voltage, thereby providing an output voltage greater than the input voltage.

Abstract: A dual-reflector antenna system (40) is provided for generating a shaped main beam radiation pattern (20) and at least one additional secondary spot beam radiation pattern (30,32). The antenna system (40) includes a main shaped reflector (10) having a shaped reflective surface (11) operatively coupled to a subreflector (12) for communicating therewith. A main feed horn (14) communicates directly with the subreflector (12) so as to reflect first energy to and from the main reflector (10) within a shaped beam radiation pattern (20). In a preferred embodiment, the subreflector (12) has an ellipsoidal reflective surface (13) which communicates directly with the main reflector (10) via an inverted reflective path (17) which has a converging focal point (18). One or more auxiliary feed horns (24,26) are operatively coupled directly to the main reflector so as to directly communicate therewith and reflect second energy within one or more additional radiation patterns (30,32).

Abstract: A magnetic torquing system for a spacecraft using conducting coils is disclosed. In one embodiment, the conductors (44, 46) on a spacecraft's (10) solar wing (28, 30) which connect the solar cell strings (38) to the voltage controller (48) are wired to produce a magnetic torque which can be regulated by shunting individual strings to ground (52) or by opening a string circuit. This embodiment does not require the extra weight of a coil because the panel's solar string produces the torque normally produced by an additional coil. In another embodiment, a coil (44, 46)is wired between a shunting switch (54) in the spacecraft voltage controller (48) and a ground (32) so that shunting a string to ground (52) supplies current first to the coil to generate a magnetic torque in the desired direction.

Abstract: The estimation and compensation of fixed, but unknown uncertainties of a thruster (22) for improving satellite attitude estimation and control as well as eliminating the need for nutation damping devices is disclosed. A thruster (22) is fired and an attitude state is estimated using an estimator (116). A commanded rate change (122) is calculated, which is modified using a compensating feedforward command (126) as updated by a fixed uncertainty estimator (124) unless an estimated rate is less than an absolute value of a threshold rate. The modified commanded rate change (130) is used to incrementally adjust thruster fire on-time (104) until a predetermined satellite trajectory is reached.

Abstract: Equalized offset fed east and west shaped reflectors (12) and (14) and technique for producing the same are provided herein. A first shaped reflector (12) has a first shaped reflective surface (3) formed to provide a first shaped beam radiation pattern (22). Dimensional deviations such as deviations (X) and (Y) are measured between the first shaped reflective surface (13) and a parent surface (30). A second shaped reflector (14) is formed with a shaped reflective surface (15) which has dimensional deviations superimposed on the other side of the parent surface (30). The second shaped reflector (12) is rotated 180 degrees relative to the first shaped reflector (14). The first and second shaped reflectors (12) and (14) are then placed in a configuration opposite one another and have shaped beam radiation patterns (22) and (24) which are substantially equal to one another. In addition, feed horns (18) and (20) are operatively coupled to the first and second shaped reflective surfaces (13) and (15) respectively.

Abstract: A spacecraft power bus regulation method and apparatus for a spacecraft. The spacecraft has solar arrays (10) and a battery (30) coupled to the spacecraft power bus (32) to drive electrical loads (34). A bus voltage limiter (38) controls the flow of current from the solar arrays while a bidirectional battery controller (36) controls power flow into and out of the battery. A processor (46) monitors current flow and battery condition using sensors (40, 42, 44, 48) and controls the bus voltage limiter accordingly. Auxiliary control is provided by the solar array drive (24) which controls the orientation of the solar arrays with respect to the sun.

Abstract: An improved bandpass frequency selective surface is disclosed which provides a wide pass band and reflection band with low loss at varying angles of incidence, low cost, low volume and light weight. The improved bandpass frequency selective surface of the present invention includes a mesh-patch array 10 disposed on at least a portion of a surface wherein the mesh-patch array 10 includes a square grid 12 surrounding numerous squares 20, 21, 22 and 23. A specific teaching of the invention concerns the design of the elements of a mesh-patch array 10 such that the frequency selective surface transmits or reflects the desired microwave signals.

Abstract: A method and apparatus of determining the fill fraction of a liquid in a spacecraft in weightless space is disclosed. A small motion is introduced about the center of mass of the spacecraft undergoing steady spin and/or thrust, and resulting spacecraft oscillations are sensed. The measured frequency, amplitude and phase of the spacecraft oscillations are compared with counterpart values predicted for possible liquid quantities by a nonempirically computed model of spacecraft dynamics.

Abstract: A direct-sequence multiple-access code division (DS-CDMA) communication system accommodates a multiplicity of separate transmitters (12) and at least one base-station receiver (14). Each transmitter generates a transmitted signal (16) at a common carrier frequency. Each transmitter has an assigned spreading code. Each bit time within the transmitted signal includes a unique signature waveform (21) generated from the spreading code that identifies the source of the transmitted signal. For a given transmitter, the transmitted signals from the other transmitters represent "multi-access noise" that may adversely degrade the signal-to-noise ratio (SNR) of that transmitter's signal at the receiver. Each transmitter operates using a spectrally inefficient power spectrum, i.e., a non-flat power spectrum, that simplifies the transmitter circuits.

Abstract: A plural cavity structure (10), suitable for use as a microwave filter (34, 34A, 34B) , has plural cavities (24, 26, 28, 30) disposed within a cylindrical aluminum housing (12) and having a central planar transverse wall (18) including an iris (38) for coupling of electromagnetic power between two successive ones of the cavities (28, 26). The transverse walls are bowed, and peripheral regions of the walls are clamped by metallic rings (66, 68, 70, 72) differing in their coefficients of thermal expansion. Thus, the rings (68, 70) of the inboard transverse walls (16, 20) are formed of titanium having a relatively high coefficient of thermal expansion, while the rings (66, 72) of the outboard transverse walls (14, 22) are formed of INVAR having a relatively low coefficient of thermal expansion.

Abstract: A method and apparatus incorporating a single self-compensating diode power detector in the feedback loop of a pulsed amplifier for exploiting the discontinuous nature of the pulsed amplifier to extract any thermally induced error voltage by a single power detector between the transmission bursts and use it to correct the power detector voltage during the bursts to obtain a true power indicative voltage, independent of temperature variation.

Abstract: A digital cellular system (10) employs a decoder that decodes control messages encoded by a convolutional tail-biting encoding procedure. The control messages (57) contain 65 bits that are encoded in a 260 bit data frame (59). The decoder reads (112) the first x quadruple bits and writes them also at the end of the data frame bit stream. A Viterbi decoding algorithm (114) is applied to the modified bit stream for x plus 65 steps. A bit stream of (65+x) bits is selected (116) from a best value path and y first bits are discarded from the selected stream. The output decoded message (118) includes bits (y+1) through (y+65).

Abstract: Cellular handoff is improved by tailing or adapting the measurement time based on the characteristics of the received signal intensity or power. More particularly, base stations typically measure mobile signal power in order to determine the necessity for handoff and the identity of a new cell. The measurement time must be of a duration which is sufficient to characterize the environment of the mobile. In accordance with the invention, the duration of the measurement time is determined from the received signal itself. Once the duration of the measurement time is determined, that data may be passed to a target cell along with other handoff data.

Abstract: A cellular radio-telephone system has a plurality of cells each of which has S sectors. The cells are grouped into a plurality of clusters each of which has N adjoining cells. Each cell has a set of assigned system frequencies with respective frequency subsets assigned to its sectors so that N groups of co-channel cells exist with each co-channel cell group including one cell from each cluster having channel frequencies corresponding to those for its co-channel cell group. Respective base station antennas are located in the respective sectors of the respective cells, and each of the cell sectors has a plurality of subscriber station directional antennas disposed at predetermined locations within the sector for communication linkage with the associated base station antenna. The cells are generally formed in rows and columns and further are formed to provide a predetermined relative orientation pattern for co-channel cell sectors.

Abstract: A connector assembly for interconnecting microwave integrated circuit modules where each module has at least one microwave interconnection pin and one DC power pin. A groundplane (28) supports the mounting surfaces (32) of the modules (10) and has a plurality of holes (38, 40) for receiving the interconnection pins (18) and the DC power pins (22) of the modules. A conducting layer (78) opposite the mounting surface of the groundplane receives microwave signals from the interconnection pins extending down through it and communicates these signals between different modules. Resilient bellows and stripline are used to ensure matched impedances and secure microwave connections. The DC power pins extend through the conducting layer (78) and isolating groundplane (28) and a DC power grid board (88) where an electrical connection is made with each DC power pin.

Abstract: A waveform classification system uses a detector 10 for detecting an analog input x(t), as well as sampler 14 and quantizer 16 to convert this analog input into a series of digital values {J.sub.k-1, J.sub.k, J.sub.k+1 }. This series of digital values {J.sub.k-1, J.sub.k, J.sub.k+1 } is represented by a fixed number of quantized digital values. A collection of predetermined feasible values is held in a feasible set table 20. A waveform classifier 18 compares the digital series from the quantizer 16 to the predetermined series held in the feasible set table 20. The waveform classifier 18 has an output, f(Z.sub.k), that marks the data in the digital series as either high or low interest. Low interest data can either be eliminated or reduced in priority to improve the overall system performance.

Abstract: A modulator capable of providing a fractional sample or symbol 995486 time employs a decimation counter (23) responsive to a clock having a frequency equal to M/N.times.(data symbol clock), where M is an interpolation factor and N is a decimation factor, for generating a data symbol clock to select FSK symbols from a sampled data array (21). A multiplier (26) receives the FSK symbols and multiplies the symbols by a weighting factor determined by the decimation counter. When the decimation counter wraps around due to a modulo M operation, a fractional weight is calculated for the current FSK symbol, then a new FSK symbol is selected, and then a fractional weight is calculated for the new FSK symbol. When the decimation counter has not wrapped, the full weighting, N, is output for the current FSK symbol.

Abstract: A mobile telephone system multiplexes plural voice traffic channels on a single carrier using a TDMA protocol. The capacity of the mobile telephone system is increased by assigning voice traffic capacity, not on a conversation basis, but on a speech spurt basis. Accordingly, delays of undetermined duration may occur between subsequent information bursts which correspond to the transmission of speech spurts. An adjustment request regarding the power with which the information bursts are transmitted from a transmitting station to a receiving station is generated by detecting an information burst transmission at the receiving station, measuring the time which elapses following the transmission, and comparing the elapsed time with a predetermined threshold value. If the elapsed time exceeds the threshold, a further transmission is requested from the transmitting station notwithstanding the availability of any information to transmit.