Abstract: Methods and apparatus are disclosed for an intrusion detection system for secure fiber optic communication systems. A guard signal is transmitted over the optical fiber communication link and both the modal power and modal phase delay of this signal are monitored. Intrusions into the link for the purpose of intercepting information being transmitted, cause changes in the modal phase delay and power of the guard signal. These changes, when detected by the monitoring system, indicate the presence of an intruder. A fiber profile which is optimal for both transmission and intrusion detection purposes is described.

Abstract: Methods for increasing the efficiency of satellite constellation operations are disclosed. The steps of the present invention comprise calculating the maximum number of communications signals that each satellite in the satellite constellation can generate, determining an operational constraint on each satellite, the operational constraint limiting the number of communications signals that each satellite can radiate substantially simultaneously, determining an operational space for each satellite wherein the operational space is defined using the operational constraint and the calculated number of signals, and using the operational space for each satellite in the constellation to determine the operational point for the constellation.

Abstract: A satellite communication system has a first deployment of a plurality of satellites deployed in a medium earth orbit and two later deployments of a plurality of satellites deployed in the medium earth orbit. The first deployment is spaced so that the second deployment may be easily deployed and interleaved into the first deployment. A ground terminal is used for communicating with the satellites in the first and second deployments.

Abstract: A method, apparatus, article of manufacture, and a memory structure for multicasting data in a cellular personal access communication system is disclosed. The method comprises the steps of allocating a multicast packet terminal identifier to a multicast group when a subscriber unit in a cell requests membership in the multicast group, receiving a multicast packet having a global multicast address, determining a cell identifier from a mapping of the global multicast address to at least one local multicast identifier and a cell identifier, and forwarding the multicast packet to the cell according to the cell identifier. The apparatus comprises a radio port controller unit having a packet data control unit coupled to a radio port configured to receive a multicast packet and a packet forwarding module. The packet data control unit includes an allocation module configured to allocate a local multicast identifier to a multicast group when a subscriber unit in a cell requests membership in the multicast group.

Abstract: A terrestrial communication system using satellite uplink and downlink frequencies is disclosed. A terrestrial cell site produces a signal at a satellite uplink frequency that is transmitted to a terrestrial user terminal. The terrestrial cell site receives a signal at a satellite downlink frequency that was transmitted by a terrestrial user terminal. The terrestrial cell site may include a signal nulling means in the direction of a satellite producing signals at the uplink and downlink frequencies.

Abstract: A communications system (10) and method of operating the communications system includes a high altitude communication device (12) that communicates with a plurality of user terminals and a gateway station (30). The gateway station (30) couples the users to terrestrial networks (32) and other users. The high altitude communication device (16) has a controller that generates a second beam having the first frequency to a service (26). The stratospheric platform (12) does not generate the second beam within a blocking area. User terminals within the service area outside the blocking area are configured to receive the first beam and the second beam.

Abstract: A first transmitting device is used to transmit a first signal on a first carrier frequency to a relay device. The relay device receives the signal by demodulating the first carrier frequency. Subsequently, the relay device retransmits the signal by modulating a second and/or a third carrier frequency. The signal is then recovered at one or more receiving devices by demodulating the second and/or third carrier frequencies. Further, a second transmitting device transmits a second signal on a fourth carrier frequency and the relay device retransmits the signal by modulating a fifth and/or a sixth carrier frequency. The signal is then recovered at one or more receiving devices by demodulating the fifth and/or sixth carrier frequencies. The transmitting and/or receiving devices are preferably voice terminals, such as a wireless telephones or data terminals, such as portable computers.

Abstract: An ATM network comprises a central call processor, and one or more remotely located ATM bridge nodes, whereby the call processor is separated from the switching fabric in the ATM bridge nodes. A plurality of preestablished permanent virtual paths are defined within the ATM bridge nodes. In setting up a connection, a source user terminal communicates with the central call processor to obtain the virtual path identifier associated with the virtual path to one or more destination user terminals. The user data is segmented into one or more cells that incorporate a header containing the appropriate VPI. The ATM bridge node extracts the VPI from incoming cells, and then directs these cells to the appropriate output ports in accordance with a routing table. The instant invention provides for improved network efficiency and upgradability, and is particularly suited to satellite based ATM networks.

Abstract: A satellite-based communications system operating at high data rates includes a plurality of satellites each having uplink and downlink antennas for transmitting and receiving a plurality of signals utilizing a plurality of spot beams to and from a plurality of coverage areas at a predetermined range of frequencies. The system can include, or be combined with, other systems to enable increased capacity over high population areas and ubiquitous coverage over lower population areas. A portable antenna assembly can be coupled to a user's portable or mobile electronic device for coupling the electronic device directly to a satellite. A routing switch provides routing and switching on-board the satellite and routes signals according to their desired destination.

Abstract: A payload design for a multi-spot-beam satellite communication system includes a plurality of uplink spot beam receivers and downlink spot beam transmitters, and a broadcast transmitting subsystem capable of transmitting a broadcast beam to an entire system geographical service area. An input filter-switch-matrix (IFSM) controllably selects input IF signal bands for routing to an on-board digital signal processor-router (DSPR). The DSPR subsequently routes all received point-to-point and broadcast data packets to the appropriate downlink spot or broadcast transmitting subsystems for transmission thereof. The broadcast downlink allows broadcast transmissions to occur at the highest efficiency possible, while also allowing for flexible provision of surge capacity for point-to-point transmissions on previously exhausted spot beams by selective use of the broadcast beam for such point-to-point transmissions.

Abstract: A method and apparatus for mitigating communications interference between satellite communications systems in different orbits is disclosed. The method comprises the steps of evaluating a geometrical relationship between a second ground station and the satellites in the second satellite constellation, and directing communications between the second ground station and the second satellite according to the evaluated geometrical relationship. In one embodiment communications are handed over from a first satellite to another satellite when the first satellite is no longer at the highest elevation angle of visible satellites. In another embodiment, handover occurs when the first satellite drops below a minimum elevation angle.

Abstract: A signal processing circuit for satellite communications signal includes a first one dimensional digital beam forming circuit for forming a beam signal in a first direction and a second one dimensional digital beam forming circuit for forming a beam in a second direction. A direction filtering circuit is coupled between the first one dimensional digital beam forming circuit and the second one dimensional digital beam forming circuit. The filtering circuit determining a communications signal direction of the satellite communications signal and tunes the filter to reduce a filter bandwidth and a frequency range of said beam signal prior to processing through the second one dimensional digital beam forming circuit.

Abstract: A method and system for controlling a movable appendage on an aerospace vehicle independent from the position of the aerospace vehicle. First and second beacons containing actual position information for the movable appendage are tracked and acquired by first and second beacon tracking sites. The beacon tracking sites report the azimuth and elevation data relating to the position of the movable appendage to a processor where a correction command is determined based on an error calculated from the position data and a desired position. The correction command is communicated to the movable appendage so that appropriate correction to the desired position can be made.

Abstract: An integrated circuit is protected from reverse engineering by connecting doped circuit elements of like conductivity with a doped implant in the substrate, rather than with a metallized interconnect. The doped circuit elements and their corresponding implant interconnections can be formed in a common fabrication step with common implant masks, such that they have an integral structure with similar dopant concentrations. The metallization above the substrate surface can be designed to provide further masking of the interconnects, and microbridges can be added to span strips of transistor gate material in the interconnect path.

Abstract: Methods for operating a satellite constellation are disclosed that utilize spatial diversity and directional gain antennas at ground terminal locations to provide multiple data rate services on a single frequency channel. One method comprises receiving a signal at a first and second satellite in the satellite constellation from a first communications device. A communications channel at a first frequency from the first satellite is used to communicate with the first communications device. A signal from a second communications device is received only at the second satellite at the first frequency, and the second satellite is used to communicate with the second communications device at the first frequency without substantially interfering with the communications with the first communications device.

Abstract: A switching device and method for selecting among a plurality of hosts on a bus, such as a Universal Serial Bus (USB). The switching device includes a first hub to be coupled to first host controller and a second hub to be coupled to second host controller. A first selection device is to be coupled to a first peripheral device and the first and second hub devices. The first selection device is to selectively couple the first peripheral device to one of the first and second host devices in response to a selection signal. A second selection device is to be coupled to a second peripheral device and the first and second hub devices. The second selection device is to selectively couple the second peripheral device to one of the first and second host controllers in response to the selection signal. The selection signal is generated in response to one of the host controllers.

Abstract: A casting head having a variably displaceable cavity surface. The casting head comprises a cavity, at least partially formed by plurality of surfaces, including a carrier surface adjacent the cavity, and a variably displaceable drive surface for controlling a pressure of a viscous casting material in a region proximate the carrier surface. In one embodiment of the invention, the casting head further comprises a doctor blade, disposed proximate the carrier surface, forming a gap therebetween for egress of the casting material. In another embodiment of the casting head, the variably displaceable drive surface is comprised of a piston. The piston is actuated by a driver-controlled motor according to a pre-determined displacement program, or according to the level of the casting material in the cavity.

Abstract: An optical communication terminal transmits data via an optical signal with a transmit mirror positioned to direct the optical signal. The optical communication terminal includes a processor configured to develop a control signal for a mirror controller to establish an optimal position of the transmit mirror. The optical communication terminal further includes a modulator coupled to the processor that modulates the optical signal in accordance with a position of the transmit mirror during transmission of the optical signal. The optimal position of the transmit mirror may be established by a scanning routine that adjusts the position of the transmit mirror to a plurality of predetermined offset positions during transmission of the optical signal. The intensity of the optical signal as received by a further optical communication terminal is then determined and provided via modulation of a further optical signal transmitted back to the first-named optical communication terminal.

Abstract: A satellite payload architecture for interactive data distribution and broadcasting services preferably for use in the emerging EHF (20-60 GHz) frequency bands. The system allows many individual service-program providers to transmit their service-program data to the satellite, on a bandwidth-on-demand and as-needed basis, directly from their premises through low-power, low-cost broadcast satellite terminals. The satellite payload utilizes high-gain spot beams for low-cost uplinking, digital regeneration and multiplexing of the individual received service-program data into MPEG transport streams, and broadcasting these in a DVB-compatible format via full-area broadcast beams to very small, low-cost end-user satellite terminals. All end-user satellite terminals are also equipped with transmit capability of a reverse-channel in support of interactivity-communications and network signaling/control functions.