Abstract: A non-contacting waveguide "T" switch (10) is provided including a stator (12), a rotor (14) mounted for rotation relative to the stator, and a coaxial conductor (64) located at the axis of the rotor for carrying a coaxial transmission. The stator (12) has at least one waveguide port (32). The rotor (14) includes a through-waveguide (48) and an impedance matching transformer (52) disposed in the through-waveguide (48) for converting the coaxial transmission into a waveguide transmission. The transformer (52) has a bore which forms a non-contacting sleeve about the coaxial conductor (64). The through-waveguide (48) carries the waveguide transmission radiated from the transformer to the at least one waveguide port (32).

Abstract: A cellular system uses dynamic repartitioning and channel packing to improve capacity without impacting quality. Dynamic repartitioning is employed to convert a carrier which operates, at one time, as an analog carrier to operate, at a later time, as a digital carrier in response to changes in offered traffic. Alternatively, a carrier which, at one time, operates as a digital carrier is converted to operate, at a later time, as an analog carrier in response to changes in offered traffic. Channel packing is used to allocate as many digital channels as possible to as few digital carriers as possible. In a preferred embodiment, both repartitioning and channel packing are implemented in response to call origination or call termination.

Abstract: An address filter for a transparent bridge interconnecting two local area networks (LANs) is disclosed. The address filter is capable of determining from an address contained in a frame issued on one network if it should be transferred to a second network. The address is verified by determining a most likely address from a search tree. The search tree has a path which is defined by pairs of address bits. At the end of each path within the search tree defined by the address bit pairs is a term node. The term node identifies a location within a compare table which contains the most likely address matching the frame address. The two addresses are compared to make a copy decision. Node addresses which are added to a network can be learned by the filter. The search tree and compare table are reconfigurable by a host processor to accommodate learned addresses.

Abstract: A personal assistance system and method for use with a cellular communication system operating over a cellular communication band and having a plurality of cell-sites. A transceiver transmits to the cell-sites a spread spectrum burst of pulses including a service request codeword indicating a request for service from a service provider. A proxy cell-phone, coupled to a preferred one of the cell-sites, originates a cellular call on the cellular communication system to a destination number of the service provider and on behalf of the transceiver to thereby create a cellular communication link between the transceiver and the service provider. A transceiver location feature provides the service provider with the geographic location of the transceiver.

Abstract: This invention discloses a method for determining when an orbiting satellite (10) is eclipsed from the sun in order to remove control torques to the satellite (10) which compensate for the disturbance of solar pressure on the satellite (10). A current measuring device (46) measures the current traveling through a particular circuit associated with the satellite (10) which is indicative of the satellite batteries being discharged, as would occur during an eclipse. The measured current is applied to a threshold logic circuit (48) which sends a signal to a control compensator (36) if the measured current exceeds a predetermined threshold level. Consequently, the compensation provided by the control compensator (36) removes the compensation for compensating for solar pressure when the satellite (10) is in an eclipse. In a second implementation, the threshold logic circuit (48) is replaced with a proportionality logic circuit to compensate for the effects of partial eclipses.

Abstract: An active phased array is provided that includes a plurality of subarrays (20) having an upper RF radiating panel assembly (22) including a plurality of radiating waveguides (26) and a feed waveguide (24) all formed of aluminum. RF radiating slots (28) are cut into one wall of each of the radiating waveguides and a silver-quartz mirror (42), with corresponding slots (44), is bonded to the outside surface. The array further includes a non-RF radiating lower aluminum support panel assembly (34) with a silver-quartz mirror (46) bonded to the outside face. The mirrors efficiently radiate thermal energy in the presence of sunlight. An active electronics module (30) is mounted in an aluminum housing, and includes an RF probe (56). The module 30 is supplied with RF signals, control signals and DC bias voltage over transmission lines contained in a multilayered circuit board (32). RF energy emitted by the probe is coupled from the feed waveguide to the radiating waveguides.

Abstract: System for providing self-selection arbitration among a plurality of slave processors connected to a VME back plane. The slave processors are connected to a common ID bus, interrupt line, and acknowledge bus. Slave processors contend for access to the VME back plane by asserting an interrupt level unique to a group of slave processors on the interrupt line. Simultaneously, the contending slave processors apply their respective addresses to the ID bus. When a contending slave processor receives an acknowledge over the acknowledge bus from a master processor, and senses its own address on the ID bus, it has successfully won the right to transmit data over the data bus.

Abstract: A diversity combiner for use with the maximum likelihood sequence estimator is disclosed. First and second receive channels produce demodulated replicas Z.sub.1 (k) and Z.sub.2 (k) of the transmitted symbol data I(k). The two signals are processed in a Viterbi equalizer to obtain a single branch metric calculation based on the two signals Z.sub.1 (k) and Z.sub.2 (k) . The Viterbi equalizer provides an estimated value of I(k) based on this single branch metric calculation, which is used for channel estimator for both antennas.

Abstract: TDMA timing is maintained by the use of visibility information transmitted among the stations in a conference. Each station monitors the identity of stations from which bursts are received. A station also receives visibility information from other stations. The station combines the information to maintain a two-dimensional Visibility Designator Byte matrix or array. A station participates in the process by periodically transmitting its own VDB array to other stations. The stations then, independently, identify a prime station by using the collected and processed information. Using the same information, a station also identifies the manner in which it will lock to the timing of the prime station.

Abstract: A lower order Viterbi system for estimating symbols being transmitted over a digital cellular channel. The received signal is oversampled at a rate at least twice the frequency of the symbol duration. The energy contained in the main and interference symbol signal is thus sampled and permits a superior BER to be obtained. The branch metric for the lower order Viterbi algorithm is calculated using both signal samples. Channel status information is individually estimated for both samples, further improving system BER. The channel status is obtained for both frequency offset errors, amplitude fading and phase occurring within the channel.

Abstract: A receiver designed for use in a mobile environment, which includes an adaptive equalizer driven by phase estimation and rotation circuitry, and which is operable in multipath fading channels. The present invention uses an AFC loop and a phase rotation circuit in front of the adaptive equalizer to improve equalizer performance in the fading channel. The present invention uses .pi./4 phase rotation circuitry before a phase quantization decision is made. This .pi./4 phase rotation circuitry allows for decisions to be made on a QPSK constellation, rather than on an input 8PSK constellation, thus improving detection performance.

Abstract: A method and apparatus for balancing environmental disturbance torques acting upon a satellite (10) by tilting the satellite solar panels (14,16) toward or away from the sun to change the solar pressure acting upon the satellite (10) as well as the gravity gradient torque generated by different panel (14,16) tilt angles. By balancing the disturbance torque acting upon the satellite (10), satellite disturbances are minimized so that the satellite stabilization system can be made smaller and fuel used for satellite attitude control is minimized. Torque balancing is accomplished at the beginning of the mission through a linear actuator (37) at the mounting location of each solar panel (14,16) to the satellite main body (12) and, once set, is passive and does not require continuous active satellite control.

Abstract: A method of attitude control for spacecraft with flexible structures utilizes an estimator/state controller pair with on-board time-varying gain scheduling. The control method includes an attitude estimator (100) for each axis, which uses rate input from inertial reference sensors (4, 5, 6) to produce estimates (37, 38, 39) of each of the state variables. The estimator employs a predictor-corrector structure which computes initial rate and position estimates for each sample interval and corrects these values by weighing them with iteratively-calculated time-varying gains according to equations 35 and 36. The state controller (40) for each axis operates on these inputs, combining them with position and rate commands (41, 42) and weighing the results with time-varying gains calculated iteratively for each sample period according to equations 46, 47, and 48. The final result is a commanded control acceleration (50) which is forwarded to a thruster modulation logic.

Abstract: The three axes thruster modulation (8) of the present invention accepts three axes of input torque commands or angular acceleration commands and generates thruster selection and thruster timing (40) information which is used to fire thrusters (48) for the purpose of spacecraft attitude control and velocity change maneuvers. The modulation logic (8) works in all three axes simultaneously and is suitable for use with an arbitrary thruster configuration, including a configuration in which individual thrusters or thruster groups do not produce torques about mutually orthogonal axes. After thruster selection and on-times have been determined, the modulation logic (8) uses this information to compute a best estimate of the actual rate change (42) which is then compared to the commanded rate change (44) to develop a residual unfired rate change.

Abstract: A Ku band frequency signal transmitter using a minimum of Ku band signal processing components is shown. Inexpensive generation of Ku band signals is provided by frequency multiplying high power, lower frequency signals to a final Ku band signal frequency. The transmitter generates an intermediate frequency signal from a baseband modulated signal and a high frequency local oscillator signal. The baseband signal is FSK modulated and has a constant envelope. A dividing stage reduces the baseband frequency signal to improve the spectral purity of the final Ku band output signal.

Abstract: A control system and method for causing a spacecraft (10) initially spinning about a principal axis of inertia (H) to transition to spin about an arbitrary command axis (3) is presented in which the capture maneuver is performed in a way to preserve spacecraft attitude knowledge without sensor or attitude propagation by using a simple rate feedback loop. The capture is accomplished by applying a step torque about axes (1) and (2) transverse to the desired spin axis (3) creating an initial nutation. The nutation is subsequently damped actively by closing a rate feedback loop with a low pass filter and applying transverse torques proportional to the transverse nutational rate.

Abstract: A new basis vector search process that directly results in an optimal linear weighting for a VSELP (Vector Sum Excited Linear Prediction) coder, thus avoiding the need to perform an extensive search. In the present invention, the conventional search process is replaced by a direct formula, thus avoiding the time consuming searching procedure. Using a simple mathematical relationship, the process of filtering the basis signals with an impulse response filter h(n) every subframe is avoided. A simple theorem has been developed to reduce the computation involved in carrying out the filtering of the basis signals with h(n), and is referred to as the switching convolution theorem. As a result, the computation time necessary to produce the optimal weighting is reduced by a factor of from 3 to 4, while maintaining the output quality of the coder. The new apparatus and method are based upon a set of equations that includes several experimentally justified assumptions.

Abstract: A transformer driver having an unlimited duty cycle capability is disclosed herein. The transformer driver 10 of the present invention is coupled to an output circuit 20 and includes a transformer 32 having primary winding and secondary windings 30 and 34. The inventive driver 10 further includes a generator 26 for applying a plurality of charging pulses P1, P2 to the primary transformer winding 30 to keep the transformer from being saturated. A transistor buffer network 36 selectively electrically isolates the output circuit 20 from the transformer. In a particular embodiment the charging pulses P1, P2 serve to maintain the voltage at the control terminal 38 of a power transistor included within the output circuit.

Abstract: A circularly polarized wave entering the horn is converted to a linearly polarized wave which appears in one of the ports depending on the sense of the polarization. The stepped configuration of the impedance matching section minimizes mutual coupling among horns of the respective assemblies of the array antenna.

Abstract: A linearizer particularly valuable for millimeter wave satellite communications is disclosed. A satellite (12) divides signal into linear (20) and nonlinear (32) paths which are converted to finline. A pair of beamlead PIN diodes (48) and a pair of varactor diodes (52) extend across the finline linear path to constitute an attenuator and phase shifter. A pair of anti-parallel Schottky diodes (60) and a pair of PIN diodes (64) extend across the nonlinear path to constitute a limiter and an attenuator. A combiner (30) combines the linear and nonlinear signals for input to an amplifier.