Abstract: Methods are provided for determining and enhancing the service efficiency of mobile communications. To assess communication efficiency in each communication region of interest, a signal-fading record is generated for that region and this record is then analyzed to find availability and energy cost for each of a plurality of power-control parameter sets. The results facilitate the selection of power-control parameter sets that enhance system efficiency in each communication region.

Abstract: An improved satellite communication device and system are provided. The satellite communication device uses yaw or roll-yaw steering to linearize angular track of uplink cells; one-dimensional linear “ratcheting” in an uplink antenna to maintain resource allocation of uplink cells along antenna columns; phased-array downlink antennas which can track earth-fixed downlink cells while compensating for the yaw (or roll-yaw) satellite steering; and variable rate TDMA service among downlink cells in a footprint. As a result, system overhead for performing new resource allocations between satellite handovers is minimized, thereby reducing resource management and increasing system capacity. Flexible bandwidth/capacity assignment of both uplink and downlink resources to earth locations via linear cell ratcheting, uplink RF peaking switch, and data-driven variable-TDMA downlink phased-arrays, is provided.

Abstract: A method for reducing blocking artifacts in digital images is disclosed. An original image is segmented into pixel blocks and mapped into a set of images associated with a predetermined compression format to produce a second image. Pixel block border pixel values in the second image are compared and adaptively adjusted to produce a third image with reduced border discontinuities. Non-border pixels within the third image are replaced with pixels from the original image to produce a fourth image that maintains fidelity to the original image. A blockiness metric may be used to repeat the mapping, comparing, adjusting, and replacing steps until blockiness crosses a predetermined level.

Abstract: A communication system and method for reconfigurably transmitting and receiving signals via a multi-beam reflector antenna array are disclosed. The multi-beam antenna system comprises a plurality of rings of single beam reflectors, each reflector having its own feed, wherein the plurality of rings are substantially concentric or nested and disposed on separate planes such that the reflectors of adjacent rings are substantially interleaved. The method, in one embodiment, comprises generating beams from a first, second and third ring of single beam feeds, respectively reflecting each beam from the first, second and third ring of single beam feeds on a separate reflector to a substantially separate coverage area, wherein the first, second and third rings are substantially concentric and disposed on separate planes such that the reflectors of adjacent rings are substantially interleaved.

Abstract: A system of inclined geosynchronous satellite orbits has a service area defined on a surface of the earth. The service area has elevation angles greater than a predetermined minimum elevation angle from the horizon. A satellite has an orbit with respect to the earth having a sky track when viewed from within said service area. An operating arc is defined by a subset of points on the sky track within the service area. The satellites operate consecutively on the operating arc.

Abstract: A method for beamforming signals for an array of receiving or transmitting elements includes the steps of selecting a beam elevation and azimuth and grouping elements of an antenna array into element ensembles that are substantially aligned with a wavefront projection on the antenna array corresponding to the selected beam elevation and azimuth.

Abstract: A logic device for performing a plurality of logic functions employs a plurality of logic elements interconnected by a plurality of switching boxes. A set of configuration bits are provided to the logic. The configuration bits represent a logic circuit that has been partitioned into two or more contexts. A subset of the configuration bits representing the portion of the logic circuit to be performed is selected by a number of context input lines. Operand bits are also provided to the logic element. By using virtualization registers, the output of a logic element in one context can be used as an input in another context. The output for a logic function is selected by the operands and stored in a register bank in such a way that it may later be retrieved by the context number it is associated with.

Abstract: A light weight fuel tank for a hydrogen powered airplane used as a platform for communication repeaters for communication services. An outer spherical shell member of a sandwich configuration surrounds an inner thin walled spherical shell member in which the liquid hydrogen is contained. A radial gap between the shell members is evacuated to a high vacuum. The facing surfaces of the shell members are coated with a low emissivity material. Electrical heaters are provided to control the evaporation rate of the hydrogen to match the fuel usage and to prevent icing during ascent and descent of the airplane.

Abstract: A laser comprising a master oscillator and a loop phase conjugate mirror (Loop-PCM) for substantially eliminating transient relaxation oscillations to instead form controlled sustained pulsations. In a preferred embodiment suitable for material processing applications with high power requirements, the master oscillator is part of a Phase Conjugate Master Oscillator Power Amplifier (PC-MOPA). A method for processing a material using a Loop-PCM by determining and using an optimal pulse fluence, duration and spacing is provided. Using pulses of the kind which are produced by the transient, and normally not desirable, relaxation oscillations common to Nd:YAG and other lasers, relaxation oscillations with controllable pulse duration, repetition rate and duty cycle are generated, making it ideal for materials processing.

Abstract: A method and system for determining the position of an object, such as an aircraft, utilizes two-way ranging with a polystatic satellite configuration and ground radar. A ground transceiver at a first known location provides a bidirectional communication path between the ground transceiver and the object wherein the ground transceiver transmits a first ranging signal to the object and the object transmits a second ranging signal to the ground transceiver in response to the first ranging signal. A first communication transceiver at a second known location provides a first unidirectional communication path between the first communication transceiver and the object wherein the first communication transceiver performs one of transmitting a third ranging signal to the object and receiving a third ranging signal from the object in response to the first ranging signal.

Abstract: A multiple beam phased array includes a plurality of array elements partitioned into a plurality of array element groups for forming a plurality of beams wherein each array element group has a taper center located to minimize maximum array element power for the plurality of beams.

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 signal utilizing a plurality of spot beams to and from a plurality of coverage areas at a predetermined range of frequencies. The system also includes a plurality of user terminals for transmitting and receiving signals to and from the plurality of communications satellites at the predetermined range of frequencies and at one of the first plurality of data rates. Each of the user terminals having a steerable antenna for tracking relative movement of each of the user terminals with respect to each of the plurality of communications satellites are for tracking movement of each of the plurality of communications satellites in order to maintain communications with the plurality of communications satellite.

Abstract: A novel mobile satellite communications technique for hand-held terminals includes a satellite system having a plurality of individual satellites all in communication with a ground telecommunications hub. A signal processed by the ground telecommunications hub is radiated through multiple paths to a plurality of the individual satellites in the satellite constellation simultaneously. The radiated signal is then re-radiated by the plurality of individual satellites to a mobile satellite terminal that receives the re-radiated signal from the plurality of individual satellites simultaneously such that the same frequency spectrum may be re-used by another mobile user.

Abstract: A lens for angularly overlapping a central portion of an optical beam with an outer portion of the beam is disclosed. The lens comprises a lens body having an optical axis, a rear surface on said lens body for receiving an optical beam, and a front surface on said lens body that includes inner and outer portions. The outer surface portion is inclined at a greater angle from the optical axis than the inner surface portion so that the outer portion of a beam transmitted through the lens from its rear surface to said outer surface portion is refracted by a lesser angle than an inner portion of the beam which reaches said inner surface portion.

Abstract: A polarization insensitive optical attenuator is disclosed. Three birefringent wedges are disposed along an optical path with their respective optical axes aligned. The apex angle of the second wedge equals the sum the apex angles of the first and third wedges. A Faraday rotator is disposed along the optical path between the first and the second wedge. A reciprocal rotator is disposed along the optical path adjacent to the Faraday rotator. An optical signal transmitted through the attenuator may be selectively divided into three spatially separate output rays while maintaining a predetermined attenuation or substantially complete isolation from reflected signals. Adjustment of the optical rotation angles allows the attenuator to be easily adapted to a wide variety of industrial and commercial laser applications.

Abstract: A low cost highly integrated method of fabricating a heat sink on the backside of a power semiconductor device maintains device performance, improves thermal transfer, and enables reliable planar connections without having to dice the wafer or package the discrete device-heat sink assembly. An etch stop layer is formed between the wafer and the frontside power devices to protect them during backside processing and to reduce the contact resistance between the device and its heat sink. The heat sinks are formed by thinning, patterning and then plating the wafer in such a manner that the devices can be released without dicing. The heat sinks are preferably oversized so that a vacuum tool can grasp the heat sink from above without damaging the device and then compression bond the heat sink onto a planar microstrip circuit assembly, which is designed and packaged to facilitate easy replacement of failed devices.

Abstract: A satellite-based communications system operating at high data rates includes a plurality of communications satellites each having an uplink and a downlink antenna for receiving and transmitting a plurality of spot beams which may be fixed or scanned. The fixed beams may be directed to areas of high satellite use. The scanned beams may be rapidly scanned between areas of use insufficient to support a dedicated beam. The scanned beam allows potentially nearly ubiquitous coverage by using high frequency beams. To rapidly scan, beam forming networks have a plurality of phase coefficients that may be changed so that the angle of the beam may change. A controller coupled to the beam forming network may be used to change the phase coefficients in response to beam inputs such as the desired beam and configurations of the other beams on the satellite.

Abstract: An earth orbiting satellite communicates with ground-based communication terminals via a limited number of frequency channels. To maximize the amount of concurrent communication that can be accommodated, the satellite's effective service area is partitioned into cells. The position of each cell relative to nearby cells is established in support of a scheme to maximize channel reutilization. Based on knowledge of communication demand and inter-cell interference constraints, all available channels are associated with particular groups of cells having a common relative position. This establishes a preference for assigning channels to particular cell groups. As communication demand in the cells fluctuates and additional communication channels are required, the channel assignment preferences are consulted to determine which channels to assign to the requesting cells.

Abstract: A planar waveguide-to-microstrip adapter, a waveguide antenna and a downconverter all formed on a single dielectric substrate. The waveguide-to-stripline adapter is connected to the waveguide antenna and includes a tapered section attached to a microstrip line. The tapered section, which may be linear or may follow some other more complex taper function such as a Chebyshev function, adapts a signal propagating within the waveguide antenna to the microstrip line or vice versa.

Abstract: A broaching tool has a plurality of cutting teeth for broaching a small, deep hole with high precision and surface finish. Three to eight teeth are engaged in the hole for cutting at any one time. For broaching sticky metals such as stainless steel, each cutting tooth has a face angle, backoff angle and rise which are sufficiently large to prevent thermal hardening of the hole surface. A ring is provided between the front face and land of each cutting tooth having a width selected to prevent formation of axial and ring-shaped tool traces. V-shaped notches having a large radial angle and a small backoff angle are formed in the land of each cutting tooth to break chips and prevent clogging. The tool further includes a rear pilot having a plurality of smoothing teeth with a diameter larger than the finished diameter of the hole. A set of rough and fine broaching tools can be provided, with the fine tool being processed to convert it to a rough tool when it is worn beyond tolerance.