Andrew Corporation

Lucent Technologies Inc.

Lucnet Technologies Inc.

Robert Everest Johnson

George Philip Vella-Coleiro

Ruikang Yang

Sridhar Arunachalam

Mark Thomas Leney

This invention relates to a method and apparatus for reducing adjacent channel power in wireless communication systems. More particularly, the present invention is directed to a system for digitally and adaptively pre-distorting a signal that includes applying a correction to the signal before it is applied to the input of an amplifier such that the correction is equal and opposite to anticipated distortion produced by the amplifier. Thus, the correction and the amplifier distortion cancel one another resulting in a system with an overall linear transfer characteristic. In these circumstances, the adjacent channel power is desirably reduced.

Method and apparatus for reducing adjacent channel power in wireless communication systems

A predistorter including a modulator configured for use with an RF power amplifier or in an amplifier system that combines in a data structure correction factors for amplitude and phase non-linearities in the responses of the amplifier and the modulator. Correction factors for memory effects in the response of the RF power amplifier may also be calculated within the data structure from scale factors transferred into the data structure. Such a calculation may be based on a scaled polynomial. A circuit for applying the difference equation to the correction factors may also be included.

Architecture and implementation methods of digital predistortion circuitry

Current and previous input signal power measures are used to generate a combined index value that is applied to one or more composite look-up tables (e.g., an I LUT and a Q LUT) to retrieve one or more pre-distortion parameters (e.g., I and Q). In one embodiment, a combined index value is generated by concatenating current and previous power measures, where each composite LUT maps all possible combinations of the current and previous power measures to the corresponding pre distortion parameters values. By using a composite LUT for each of I and Q, the overall signal processing time of the pre-distortion processing can be greatly reduced relative to the prior art, resulting in a significantly smaller RF delay line used to delay the input signal and thereby providing a less costly and more efficient amplifier system.

Amplifier pre-distortion processing based on composite look-up tables

An apparatus for processing an analog signal includes a programmable signal converter in which a mapping between input voltages and output voltages is loaded into an input-to-output mapping device, e.g., one or more look-up tables. The resulting device has a lower cost, introduces a shorter delay, requires significantly less circuit board real estate, and has a higher operating frequency than the existing devices. An exemplary embodiment includes an analog-to-analog converter disposed in an integrated package or on a single chip integrated circuit that includes an input converter, an input-to-output mapping device and a digital-to-analog converter. The traditional encoding/decoding process on the output of the digital-to-analog conversion is replaced in this embodiment by using the input converter to drive address mapping values in the input-to-output mapping device, e.g., entries in a lookup table, thereby significantly speeding up the process.

Method and apparatus for processing analog signal

A digital synthesizer includes a memory containing values representing amplitudes of a signal such as a sinewave, a digital/analog converter for converting outputs from the memory into an analog signal, and a counter for counting by a predetermined fixed increment, which operates at a high frequency to enable the generation of very precise frequency waveforms. The digital synthesizer has many practical applications including the generation of precise signals to extract information from input radio frequency signals, the obtaining of a precise frequency from a low-cost clock, and the use as a component of a FSK modulator to permit selection between signals of multiple frequencies without any phase discontinuity. Finally, the digital synthesizer can be used in combination with an 8-bit memory, to generate a 10-bit input to a digital-to-analog converter.

Direct digital synthesizer

A demodulator demodulates a PSK communications signal using a synchronizer, a period window detector, and a logic device. The synchronizer provides a transition signal representing reference edges of the communication signal. The period window detector, coupled to the synchronizer, establishes a time interval based on the period of the transition signal. Finally, the logic device, having logic inputs coupled to the outputs of the period-window detector, yields a logic output signal. The demodulator preferably includes a carrier boundary detector for framing messages and minimizing noise detection in a manner that permits signal strength measurements over a wide dynamic range.

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Randolph, NJ, United States of America

Robert Everest Johnson