Patents Assigned to AT&T Bell Laboratories
  • Patent number: 5544328
    Abstract: Digital signals, such as digitized television signals, are subjected to a source coding step followed by a channel mapping step. The source coding step causes the signal to be represented by first and second data streams. The first stream carries data regarded as more important and the second carries data regarded as less important. In the channel mapping step, the mapping is such that the data elements of the various data streams have differing probabilities of being erroneously detected at the receiver. The channel mapping step includes at least one multi-level coding step. The signal constellations used in the channel mapping step are partitioned into supersymbols, in which the distance between the symbols comprising at least ones of the supersymbols is less than a parameter referred to as the maximum intra-subset distance (MID).
    Type: Grant
    Filed: October 31, 1991
    Date of Patent: August 6, 1996
    Assignee: AT&T Bell Laboratories
    Inventor: Nambirajan Seshadri
  • Patent number: 5486263
    Abstract: A diamond body, such as a CVD diamond film, is etched by immersion of the body in a molten or partially molten metal, such as the rare earth metal La or Ce. While the body is being etched, various portions of a major surface of the body can be protected for various time durations by masks against the etching--whereby, after dicing the body, the resulting dies can be used as submounts for lasers with feedback.
    Type: Grant
    Filed: July 2, 1992
    Date of Patent: January 23, 1996
    Assignee: AT&T Bell Laboratories
    Inventors: William C. Dautremont-Smith, John E. Graebner, Sungho Jin, Avishay Katz
  • Patent number: 5441013
    Abstract: In contrast to previous approaches, the present inventors have discovered that diamond films can be grown by carbon CVT reactions occurring exclusively in the exothermic regime, where the lower temperature (<1500.degree.C.) conditions considerably simplify the equilibrium gas phase chemistry. Under these conditions of a small temperature gradient and short transport distance between the source and substrate, supersaturation of the gas phase with regard to graphite and diamond does not attain sufficiently high values to induce spontaneous homonucleation of graphite and diamond in the gas phase. With this process, temperatures as low as 680.degree.C. were found to be sufficient to induce the growth of continuous diamond films free of non-diamond allotropes.
    Type: Grant
    Filed: March 23, 1993
    Date of Patent: August 15, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Guang-kai D. Jeng, James W. Mitchell, Lawrence Seibles
  • Patent number: 5442693
    Abstract: An integrated console for a human operator who provides listing and directory services, particularly for the 800 telephone number system, to callers via a stored program switching device employs simultaneous MS-DOS and a memory management utility, such as MicroSoft Windows.TM.. Data is exchanged between applications for MS-DOS and applications for Windows.TM. via a shared memory. Data pertaining to the directory and listing services is stored in a database which is accessed via a data network which may be a LAN or a WAN. Thus, the information in the database can be accessed by a plurality of operators on consoles in the network. Communication between the operator console and the stored program switching device is achieved via a digital subscriber line which is coupled to the console via an interface board compatible with the integrated services data network (ISDN).
    Type: Grant
    Filed: December 22, 1993
    Date of Patent: August 15, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: J. David Hays, G. Douglas Morlok
  • Patent number: 5436756
    Abstract: Photocurrent suppression is achieved without deleteriously affecting modulation performance in a surface normal, electro-absorption, quantum well modulator by introducing a sufficient number of non-radiative recombination centers in the quantum well region of the modulator. The presence of the non-radiative recombination centers significantly shortens the lifetime of photogenerated carriers and, thereby, suppresses the photocurrent. Modulation performance characteristics such as contrast ratio are maintained at acceptable levels even though exciton broadening occurs in the quantum wells. The present modulator exhibits a careful balance between defect density in the quantum wells and the acceptable degree of exciton broadening necessary to preserve quantum effects.
    Type: Grant
    Filed: September 30, 1992
    Date of Patent: July 25, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Wayne H. Knox, Jason B. Stark, Benjamin Tell, Ted K. Woodward
  • Patent number: 5434403
    Abstract: A bar code (14) on an object (12) is read a distance from the object by a television camera. The output signal of the camera is thresholded to obtain a binary signal indicative of the image information associated with at least one scan line. This binary signal is written into a FIFO storage device (28) at a rate corresponding to the rate at which the camera images the bar code. Once the binary signal is fully written into the FIFO storage device, the binary signal is read from the FIFO at a second, much slower rate for decoding by a bar code decoder (36). In this way, the image of the bar code can be obtained by a television camera which is capable of imaging the bar code at a distance, while the image information can be decoded by a bar code decoder that operates to perform decoding at a rate much slower than the rate at which the camera acquires information.
    Type: Grant
    Filed: March 23, 1994
    Date of Patent: July 18, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Israel Amir, Frank P. Higgins, John B. Macdonald
  • Patent number: 5434876
    Abstract: We have discovered that at least some optical waveguide lasers such as Er-doped fiber lasers are subject to excessive output amplitude fluctuations, including severe fluctuations when the laser is subjected to mechanical shock. We have determined that these highly undesirable fluctuations are due to a resonance phenomenon, and that the fluctuations can be at least substantially reduced by means of a feedback loop that makes the amplitude of the output of the pump laser responsive to the amplitude of the output of the waveguide laser. We have also discovered that the operation of a pump laser/waveguide laser combination is frequently improved if an appropriate non-reciprocal element (e.g., an isolator or a tilted wavelength filter) is placed between the two lasers. An exemplary embodiment of the invention comprises the feedback loop as well as the non-reciprocal element.
    Type: Grant
    Filed: October 23, 1992
    Date of Patent: July 18, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Robert M. Atkins, Jean-Marc P. Delavaux, Victor Mizrahi
  • Patent number: 5413954
    Abstract: A novel vapor phase Si cleaning process comprises simultaneous exposure of the Si surface to a flux of neutral atomic hydrogen and to a flux of ionized particles. The former flux is substantially derived from a plasma, typically a microwave plasma, that is spaced apart from a second plasma, typically a RF plasma, from which the ionized particles are derived. The novel method can be implemented at relatively low cost and facilitates adjustment of the ratio between the two fluxes to result in optimal removal of, e.g., native oxide from the surface.
    Type: Grant
    Filed: November 10, 1992
    Date of Patent: May 9, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Eray S. Aydil, Richard A. Gottscho, Zhen-Hong Zhou
  • Patent number: 5412716
    Abstract: A system of impedance matching is provided to match the total impedance of the cable system to the total impedance of the powered elements such as the repeaters. The source impedance of the power supplies may be considered as part of the cable impedance. By matching impedances, the source voltage for driving the electronics is advantageously minimized.
    Type: Grant
    Filed: May 3, 1993
    Date of Patent: May 2, 1995
    Assignee: AT&T Bell Laboratories
    Inventor: Matthew S. Blaha
  • Patent number: 5406620
    Abstract: Disclosed is a system for allocating international transit calls among a plurality of carriers in a terminating country in accordance with routing information that has been previously specified by the originating carrier. Originating carriers may select one of a plurality of routing treatment options which specify how international transit calls should be allocated among the plurality of carriers serving a given terminating country. Carrier treatment tables maintain the routing information specified by each originating carrier for each terminating country. Upon receipt of an international transit call, an originating gateway switch can access the appropriate carrier treatment table and retrieve the routing information specified by the originating carrier for the indicated terminating country. In this manner, a terminating carrier can be selected to receive the transit call based on the routing information previously specified by the originating carrier.
    Type: Grant
    Filed: December 14, 1993
    Date of Patent: April 11, 1995
    Assignee: AT&T Bell Laboratories
    Inventor: Eric T. Pei
  • Patent number: 5402516
    Abstract: Optical fiber and cable performance are assured by a category of UV-cured polyurethane acrylates. Low cost is the consequence of use of the polycarbonate oligomer. Good performance and long life are ascribed to other ingredients of the coatings. Dependence on the hindered phenols for antioxidant protection assures sufficient protection for these inherently stable materials without incurring fiber damage found to result from use of hindered amine antioxidants.
    Type: Grant
    Filed: September 30, 1993
    Date of Patent: March 28, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Lee L. Blyler, Jr., Darryl L. Brownlow, Daryl Inniss, James R. Petisce, Lloyd Shepherd, Carl R. Taylor
  • Patent number: 5387269
    Abstract: An optical waveguide is made by forming successively of light transmitting material a first clad layer (13), a core layer (15) and a second clad layer (18). The core layer has a higher refractive index than that of the first and second clad layers such that the core layer (15) can transmit light along its length as an optical waveguide. A sacrificial layer (14, 17) is formed surrounding at least a first end potion of the core layer. The sacrificial layer is selectively removed as by selective etching such that the first end portion of the core layer is separated from the first and second clad layers. With the end portion so isolated, a lens (22) can be formed on it such that light may be more effectively coupled to or from the core layer. Preferably, the lens is formed by heating the structure sufficiently to form a meniscus on the free end and then cooling it before the reminder of the core layer flows or melts. The cooling hardens the meniscus such that it constitutes an optical lens.
    Type: Grant
    Filed: September 3, 1993
    Date of Patent: February 7, 1995
    Assignee: AT&T Bell Laboratories
    Inventors: Casimir R. Nijander, Wesley P. Townsend, Yiu-Huen Wong
  • Patent number: 5384810
    Abstract: A high-speed convolutional decoder is constructed by performing the transition, or branch, metric calculations in reference to a subset of a constellation, which comprises a plurality of subsets. In addition, any subset can be chosen as the reference subset through the use of "modulo decoding." In a modulo decoder, the constellation space is folded into a modulo set area that is centered around the arbitrarily chosen reference subset. The branch, or transition, metrics are calculated within the modulo set area. As a result, the branch metric computations are only performed on a small area of the signal space, with the result that only one error is extracted, the branch metrics are easily computed, and one slicing is performed--thus reducing overall computation time.
    Type: Grant
    Filed: February 5, 1992
    Date of Patent: January 24, 1995
    Assignee: AT&T Bell Laboratories
    Inventor: Daniel Amrany
  • Patent number: 5384826
    Abstract: A cellular switching system and architecture is described in which the switching associated with a call originated within one cell but now serviced within another cell is distributed among base stations which are interconnected with each other through a local area network or a packet switch. The routing procedure associated with the point of origin for a given call is stored in the memory of a switch of public switched telephone network. As an active subscriber crosses a cell boundary, the switch routes all packets of information for the given call to the originating base station for the duration of the call. Importantly, each base station then forwards each packet to the subscriber's current base station via the local area network or a packet switch.
    Type: Grant
    Filed: July 28, 1993
    Date of Patent: January 24, 1995
    Assignee: AT&T Bell Laboratories
    Inventor: Noach Amitay
  • Patent number: 5384806
    Abstract: An ISDN modem. The modem includes an independent clock which controls the modem's input and output filters and two dependent clocks whose rates are functions of the independent clock and which are synchronized with external timing signals. When a dependent clock is synchronized, timing adjustment signals to other components of the modem specify the type and direction of synchronization. One of the dependent clocks and the independent clock are used to control a decimator which provides two samples of a symbol which are one independent clock cycle apart. One of the samples is a primary sample from which the symbol is interpreted and the other is a secondary sample which is used to continually train a jitter canceller. When a clock is synchronized, the secondary sample becomes the primary sample, providing the modem with a time-invariant echo path. On clock synchronization, the jitter canceller responds to the timing adjustment signals by providing adaptation information to the linear echo canceller.
    Type: Grant
    Filed: September 23, 1991
    Date of Patent: January 24, 1995
    Assignee: AT&T Bell Laboratories
    Inventor: Oscar E. Agazzi
  • Patent number: 5380398
    Abstract: A method for semiconductor device fabrication that uses a mixture of SiCl.sub.4, CF.sub.4, O.sub.2, and He to selectively etch GaAs with respect to AlGaAs. Etch selectivities greater than 300:1 are obtained.
    Type: Grant
    Filed: November 25, 1992
    Date of Patent: January 10, 1995
    Assignee: AT&T Bell Laboratories
    Inventor: Lawrence E. Smith
  • Patent number: 5373248
    Abstract: A transconductor includes first and second differential pair compound transistors coupled between a first reference node and a common node. The compound transistors are commoned to each other at a common node. A single current source is coupled between the common node and a second reference node. In an alternate embodiment, a current turnaround circuit may be used to convert the transconductor to a single ended configuration.
    Type: Grant
    Filed: June 8, 1993
    Date of Patent: December 13, 1994
    Assignee: AT&T Bell Laboratories
    Inventor: Francisco J. Fernandez
  • Patent number: 5372088
    Abstract: In a VGF crystal growth method, the configuration of the outer periphery of the seed crystal (15) has the same dimensions as the configuration of the inner surface of the major portion of the crucible (12).
    Type: Grant
    Filed: December 30, 1991
    Date of Patent: December 13, 1994
    Assignee: AT&T Bell Laboratories
    Inventor: Muhammed A. Shahid
  • Patent number: 5373149
    Abstract: A PCMCIA wireless credit card modem is fabricated using two credit card sized sections interconnected by a hinge. The first section contains modem circuitry, and the second section contains an antenna and radio circuitry. The two sections form a 90 degree angle in the open position. The section with the modem circuitry fits into a type I or II PCMCIA slot in a portable computer, and the section with the antenna remains on the outside of the computer. The folding electronic card assembly can interface to several different PCMCIA card slots. In one embodiment, the first section fits within a Type I or Type II PCMCIA slot, and when in the closed position, the assembly fits within a Type III or Type IV PCMCIA slot.
    Type: Grant
    Filed: February 1, 1993
    Date of Patent: December 13, 1994
    Assignee: AT&T Bell Laboratories
    Inventor: Kris A. Rasmussen
  • Patent number: RE34811
    Abstract: This invention is large N.times.N packet switch, formed using a plurality of smaller packet switches. The invention comprises an N input, L output interconnect fabric (L>N), and a plurality of J.times.K smaller packet switches (J>K). Each of the J inputs to each packet switch is connected to a separate one of the L outputs of the interconnect fabric, and each of the K outputs from each packet switch is connected to a destination equipment. In operation, packets are received at the N inputs to the interconnect fabric, and each packet is routed to one of the inputs of the packet switch associated with the destination user equipment for the packet. Simultaneous packets, up to J in number, are routed to separate inputs of a particular packet switch for distribution to their respective destinations, while all other simultaneous packets destined for user equipments associated with the same packet switch are lost, the probability of such a loss being acceptably small.
    Type: Grant
    Filed: September 4, 1992
    Date of Patent: December 27, 1994
    Assignee: AT&T Bell Laboratories
    Inventors: Kai Y. Eng, Mark J. Karol, Yu S. Yeh