Abstract: A method and system for providing a user with correction information for use in accurately determining the location of the user. A plurality of monitor stations are disposed at a plurality of known fixed locations for monitoring a plurality of navigation data messages transmitted by Global Positioning Systems (GPS) Space Vehicles (SVs) and for determining a plurality of corresponding correction factors. A central ground station is operatively coupled to each of the plurality of monitor stations for receiving the plurality of correction factors from each of the plurality of monitor stations. A GPS transceiver receives at least one of the plurality of navigation data messages at an unknown location and determines a general location of the user. The general location of the user is then transmitted to the central ground station.

Abstract: In a satellite experiencing alternate periods of light and eclipse, an electrical power control system utilizing direct energy transfer battery charging in a fully regulated electrical bus system to provide and control the system power over both the charging and the discharging cycles of the satellite electrical system.

Abstract: Data transmissions between a transponder and a reader of a toll collection system are minimized while the transponder moves through a communication zone of the system. A plurality of dimensionally programmable detection regions, are defined within the communication zone. Detection criteria are also defined that indicate whether the transponder transitions into, out of, or both into and out of one of a plurality of "in" detection regions. Then it is determined if the current geolocation of the transponder is within any of the detection regions. The current location of the transponder is compared to the previous location of the transponder. If a change in the location of the transponder occurs and one of the detection criteria has been met, a detection region report message is generated.

Abstract: Methods and systems for calibrating an array antenna are described. The array antenna has a plurality of antenna elements each having a signal with a phase and an amplitude forming an array antenna signal. For calibration, the phase of each element signal is sequentially switched one at a time through four orthogonal phase states. At each orthogonal phase state, the power of the array antenna signal is measured. A phase and an amplitude error for each of the element signals is determined based on the power of the array antenna signal at each of the four orthogonal phase states. The phase and amplitude of each of the element signals is then adjusted by the corresponding phase and amplitude errors.

Abstract: A copper-tungsten or copper-molybdenum substrate is plated with a nickel/gold plating by first activating a surface of the substrate. In activating, the surface is contacted to a concentrated alkaline solution at elevated temperature, and then to a concentrated acidic solution. The surface is thereafter plated with a nickel strike layer, plated with a nickel primary layer overlying the nickel strike layer, sintered, re-activated in a concentrated acidic solution, plated with a nickel secondary layer overlying the nickel primary layer, and plated with a gold layer overlying the nickel secondary layer.

Abstract: A high speed circular data bus system having a plurality of input buffers connected to uplink demodulator units associated with a plurality of data receivers. The input buffers are connected to each other in a daisy chain configuration with each input buffer connected to the next sequential input buffer in the daisy chain configuration and connected to an associated output buffer slice. Data received from each uplink demodulator unit is sequentially circulated through each input buffer so that each input buffer sequentially sees the data received from each uplink demodulator unit. In the preferred embodiment, each input buffers consists of an input buffer node having a primary input buffer and an associated redundant input buffer. Each pair of input buffers also being connected in a daisy chain circular configuration and cross-linked to each other.

Abstract: An electronic structure is formed of alternating layers of a metal and a cured ceramic-polymer mixture. The ceramic-polymer mixture is prepared by mixing small ceramic particles into a flowable, curable polymer. The mixture is spread over a first metallic layer and, optionally, B-stage cured. Additional metallic layers and ceramic-polymer layers are added in alternating fashion. Metallic interconnects may be provided through overlying ceramic-polymer layers to a particular metallic layer. The resulting structure is heated to a moderate temperature to cure the polymer.

Abstract: A communication and tracking antenna is formed by embedding a tracking patch array in a shaped dual gridded reflector. The reflector includes first and second reflector grids that have orthogonally arranged grid lines and are respectively fed by feed horns. The patch array is positioned so that the first reflector grid is between the patch array and the first feed horn. The first reflector grid thus serves as a filter to remove unwanted polarization components and enhance the quality of both the tracking radiation and the radiation that is reflected from the second reflector grid. In other embodiments, a tracking array is positioned adjacent a reflector's perimeter.

Abstract: A self adjusting tiled image display system and method is provided. In operation, an image source having an array of tiled image displays projects a test image pattern. A positioning device is attached to a corresponding one of the image displays for positioning that image display. A sensor senses the test image pattern projected by the image displays and generates a sensor signal indicative of the sensed test image pattern. A processor compares the sensor signal to a proper alignment signal indicative of the image displays being properly aligned to generate a positioning signal. The processor applies the positioning signal to the positioning devices to position the image displays as a function of the positioning signal until the image displays are in the proper alignment.

Abstract: A simple joining process for members of passive microwave structures is described which reduces passive intermodulation. The process forms an aperture in a first member and forms a second member to have dimension which exceeds the aperture dimension by a dimension differential. The members are joined by initially causing them to have a temperature differential that is sufficient to permit the second member to be positioned across the aperture. The dimension differential is selected to generate mutually-induced radial stresses in the members, after the temperature differential is removed, which enhance the metal-to-metal contact between the members and, thereby, improve passive intermodulation (PIM) performance. Preferably, the dimension differential is selected to cause the second member to elastically buckle and exert a buckling stress against the first member. Additional interface structures are provided to resist operational axial forces, e.g., vibration, that tend to dislodge the members.

Abstract: A system for storing and managing messages received at a satellite communications system is disclosed. Messages are sent from a plurality of transmission sources to the system. The message data is received at a plurality of interfaces that verify the accuracy of the data sent, store it in a plurality of RAMs, and then signal a processor that a new message is available for execution. The RAMs are each part of separate message buffers that keep track of the addresses of valid, stored messages and the addresses of the last messages read from memory.

Abstract: Microwave switches are shown which can route signals in an operating frequency band along selectable signal paths between a plurality of microwave ports. The switches are especially suited for forming switching systems that can substitute redundant components for failed components. In one embodiment, waveguide transmission lines and microwave ports are serially coupled in a closed loop with other waveguide transmission lines arranged transversely across the loop. In another embodiment, waveguide modules are formed of three waveguides coupled to a microwave port and the waveguide modules are serially arranged. In each waveguide of these embodiments, conductive reeds are movable between a signal-attenuating position abutting the interior surface of the waveguide and a signal-conducting position substantially coaxial with the waveguide and coupled to the microwave ports at each waveguide end.

Abstract: A computer system and a method for the protected distribution of certificate and keying material between a certification authority and at least one entity in the certification authority's domain, including the steps of sending keying material, including a password, generated by the Certifying Authority to the entity via a secure medium; generating and protecting, by the entity, a public and a private key pair using the keying material provided it by the certifying authority; generating, protecting and sending a request for a certificate to the certifying authority using the keying material provided it by the certifying authority; requesting, by the certifying authority, that the public key and address of the entity be sent to the certifying authority; protecting and sending the public key and address of the entity to the certifying authority using the keying material provided it by the certifying authority; assembling and issuing the certificate to the entity from the certifying authority and recording the pu

Abstract: An active redundancy system for high power satellite communications payloads that use multiple antenna beams driven by multiple power amplifiers and that require power redistribution among the beams during the lifetime of a payload uses a number of power amplifiers equal to or greater than the number of antenna feeder elements to provide extra output power at the beginning of life, instead of commonly used redundancy switches. As power amplifiers fail, the amplitude and phase of the signals driving the remaining power amplifiers are adjusted to maintain antenna performance. Power amplifiers having sufficient capacity are used to ensure that, given an anticipated number of power amplifier chain failures, performance requirements can be met at the end of life.

Abstract: A desired frequency response of a microwave network on a monolithic microwave integrated circuit (MMIC), a microwave integrated circuit (MIC), or a hybrid circuit is achieved by selectively switching MEM switches to change the network topology. In a filter network, MEM switches connected between capacitors and inductors are selectively switched to change the network configuration to achieve a desired frequency response. In an amplifier network, the MEM switches are selectively switched to tune the amplifier to a desired frequency response and to reduce harmonic output.

Abstract: A system (10) and method for providing simultaneous data reading and writing for a random access memory (18) include storing new data (14) and a corresponding new data address (26), comparing the new data address to a current read address (32), and substituting (38) the new data for the data at the current read address at the output (38) while simultaneously writing the new data into the memory (18). The system and method are particularly suited for application in space-based communication satellites which utilize continuous memory read accesses since the invention provides the functionality of a dual-ported RAM while being implementable with fewer gates and less complex control circuitry to provide reduced power consumption.

Abstract: A band limited Amplitude Shift Keyed (ASK) modulator employing linear modulation and an efficient Class C power amplifier. Band-limited operation is provided by filtering a digital baseband input signal prior to modulation. Closed loop feedback is employed around the amplifier to assure linear modulation over a wide modulation range which preserves the frequency characteristics of the baseband signal on the modulation envelope. Further filtering is accomplished by exploiting the closed loop system response, incorporating it in the filter characteristic as an added filter pole.

Abstract: A digital information system delivers virtual on-demand information over existing, as well as the next generation, digital transport systems by offloading a portion of the systems' peak bandwidth requirements to the local subscribers. A collaborative filtering system synthesizes the preferences of all of the subscribers and then predicts those items that each subscriber might like, and therefore request. Each subscriber is provided with a local storage device for storing, during off-peak hours, those items recommended by the collaborative filtering system. As a result, only a relatively few subscriber requests must be serviced directly from the central distribution system.

Abstract: A method and apparatus for improving aim point accuracy in a programmable flight control missile includes a communication system for receiving at least one frame of imagery in a vision system mounted in a missile, predicting a subsequent frame content based on the content of the previous frame as a function of missile path height, missile velocity, and frame rate, and creating a residual image by determining the difference between a predicted subsequent frame content and actually received frame content. In the preferred embodiment, the residual image can be transferred at a high bit rate through a communication system into a controller at which location correction data can be generated and delivered to the communication system to the missile in flight. Preferably, the predicted subsequent video frame and the sensed subsequent frame content are centrally aligned before creating a residual image.

Abstract: A phased array (20) and method for constructing the same are disclosed. The phased array (20) includes a superstructure (22) with cavities (40) therein. A cover plate (28) is mounted to the superstructure (22) and cooperates with the cavities (40) to form cavity style filters therebetween and to form a box-beam type superstructure. Ideally, the superstructure (22) is self supporting. Electronic modules (32) and amplifiers (33) are mounted to the superstructure (22). The method includes machining a block of material to form a webbed superstructure with cavities (40) therein. A cover plate (28) is mounted to the superstructure (22) over the cavities (40) to form cavity style filters. Amplifiers (32) and antenna elements (30) are then affixed to the superstructure (22) and cover plate (28). Ideally, the cover plate (28) is affixed to the superstructure (22) using an electrically conductive adhesive.