Lucent Technologies Inc.

At+t Corp.

US Government As Represented by the Secretary of the Army

American Telephone & Telegraph Co., At&t Bell Laboratories

Howard David Helms

Robert Raymond Miller, Ii

Richard Robert Shively

Steven R Johnson

Gerald Nykolak

Ranjan V Sonalkar

Paul F Szajowski

Alex Pidwerbetsky

Dennis M Romain

Dominick J Imbesi

Near-end crosstalk between identical discrete multi-tone modems is reduced by aligning the frames of all modems at a central office to each other, aligning the frames transmitted by subscribers' modems with the frames received by those modems, and including a cyclic prefix between the central office and the most distant subscriber to be served. By making adjacent DMT carrier frequencies be orthogonal to each other, the aforementioned modifications will reduce both Near End Cross-Talk and Leakage-Excited Cross-Talk. These benefits apply to modems at both the central office and subscriber ends of the communication path.

Method and apparatus for reducing near-end crosstalk (NEXT) in discrete multi-tone modulator/demodulators

In the method and apparatus for controlling the power level of a laser signal in free space communication, a communication terminal transmits an output laser beam into free space and also receives information, through a channel that is not free space laser based, about the power of the output laser beam measured at a distance and at different times. The terminal determines whether a drop in the power of the output laser beam measured at the distance is due to atmospheric effects based on the received information. The terminal increases the power level of the output laser beam to a desired level if the power drop is determined to be due to atmospheric effects. On the other hand, the terminal lowers the power of the output laser beam to a predetermined level if the power drop is determined to be due to blockage thus avoiding harm to accidental observers that might intrude into the path of the laser beams.

Method and apparatus for controlling signal power level in free space communication

A method for increasing the interrogation range of an RF Tag in a radio communication system using RF Tags with multiple reflecting antenna elements. The reflecting antenna elements are predeterminately positioned, and preferably aligned, with respect to each other in the direction of expected incident RF radiation. The reflecting antenna elements are sequentially pulsed on and off such that while the first reflecting antenna element is in a signal reflecting operating state, the remaining reflecting antenna elements are in a substantially non-reflecting state, and when the second reflecting element is in a reflecting operating state, the remaining reflecting elements are in a non-reflecting state, etc. The sequential pulsing and predetermined fixed spacing between the reflector elements generates constructive interference between the reflected signals of the reflecting antenna elements which increases the power of the resulting reflected signal.

Method and apparatus for improving the interrogation range of an RF-Tag

A digital channelizer employs a polyphase filter element in which a shift register is used to commutate time series data to a bank of polyphase filters at the inputs of an FFT module. The filter bank and FFT module are updated at a frequency that is independent of the rate that the data is fed into the buffer and filter/FFT cycle rates of less than the ratio of the input data rate to the number of input channels may be accommodated by the shift register commutation. The output of the FFT module is interpolation filtered by inserting interpolated points between adjacent data points in the channelized output stream to increase the output frequency by an integral multiple of the update rate of the polyphase filter/FFT update rate. By determining an integer, q, such that (R /R )(2N&minus;q) is a non-zero integer l, where R is a desired output data rate, R is an input data rate and 2N is the number of output channels (M<N), updating the filter/FFT at a rate of R /(2N&minus;q), and interpolation filtering by inserting l&minus;1 interpolated data between each successive pair of channelized data, a desired output data rate can be matched with an input data rate.

Digital channelizer with arbitrary output sampling frequency

A method for increasing the interrogation range of an RF Tag in a radio communication system using RF Tags with two reflecting antenna elements. The second reflecting antenna element is predeterminately positioned, and preferably aligned, with respect to the first reflecting antenna element in the direction of expected incident RF radiation and is spaced from the first reflecting antenna element at a predetermined fixed distance. The first and second reflecting antenna elements are alternately pulsed on and off such that while the first reflecting antenna element is in a signal reflecting operating state, the second reflecting antenna element is in a substantially non-reflecting state and vice versa. The alternate pulsing and predetermined fixed spacing between the first and second elements generates a known phase difference between the reflected signals of the first and second reflecting antenna elements. The phase difference is preferably 180 degrees which may be achieved by spacing the second reflecting antenna element from the first reflecting antenna element at a distance equivalent to &frac14; of the wavelength of the interrogating signals.

Method and apparatus for improving the interrogation range of an RF tag

This invention reduces near-end crosstalk between identical discrete multi-tone (DMT-type) modems by introducing the following modifications to modems at a central office or a subscriber premises. The modifications include: a mechanism for aligning the frames of all modems at the central office (CO), a mechanism for aligning the frames transmitted by the subscribers' modems with the frames received by those modems, and lengthening the DMT frame to include a cyclic prefix. The cyclic prefix to a frame has been made longer than twice the maximum round-trip delay, that is, the delay between the central office and the most distant subscriber to be served. By making adjacent DMT carrier frequencies be orthogonal to each other, the aforementioned modifications will reduce both Near End Cross-Talk (NEXT) and Leakage-Excited Cross-Talk (LEXT). These benefits apply to modems at both the central office (CO) and subscriber ends of the communication path (for example, a high capacity twisted-pair wire).

Method and apparatus for reducing near-end crosstalk (NEXT) in discrete

The present invention relates to an Operational Life Test (OLT) or 'burn-in' technique for testing microprocessors. In accordance with the present invention, an OLT chamber is provided wherein many Evaluation Boards are mounted within racks in a frame in the chamber, each Board being designed for separately exercising its associated microprocessor integrated circuit (IC). During the OLT or burn-in procedure, each Evaluation Boards runs its own internally stored diagnostics, simultaneously with other Boards, to exercise the associated microprocessor ICs while the power to the Boards and the environment within the chamber is appropriately cycled to simulate system testing, installation or normal customer use. During the OLT procedure, each Board periodically reports the status of the associated microprocessor IC to circuitry such as a computer outside the chamber in order to provide a means for determining and recording any failure of a Board.

Technique for the operational life test of microprocessors

The off axis angle detector of a radar is sampled at discreet intervals by special purpose digital computer. Each sample is directed to one of a plurality of registers in accordance to the angle indication of the sample. Each register being a counter which will give an output when it is in an overflow condition; therefore, each register acts as a threshold device. Upon one register overflowing and giving an output of that indication, the sample process is stopped and the output of the register is sent to a converter to indicate the direction of the jammer. This is done both for the azimuth and elevation angle of the radar receiver.

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Brookside, NJ, United States of America

Howard David Helms