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1047 results about "Linearization" patented technology

In mathematics, linearization is finding the linear approximation to a function at a given point. The linear approximation of a function is the first order Taylor expansion around the point of interest. In the study of dynamical systems, linearization is a method for assessing the local stability of an equilibrium point of a system of nonlinear differential equations or discrete dynamical systems. This method is used in fields such as engineering, physics, economics, and ecology.

Systems and methods for structural indexing of natural language text

InactiveUS20070073533A1Efficient structural indexingDeal with variationNatural language data processingSpecial data processing applicationsCombined usePaper document
A structural natural language index is created by segmenting documents within a repository into text portions and extracting named entity, co-reference, lexical entries, structural-semantic relationships, speaker attribution and meronymic derived features. A constituent structure is determined that contains the constituent elements and ordering information sufficient to reconstruct the text portion. A functional structure of the text portions is determined. A set of characterizing predicative triples are formed from the functional structure by applying linearization transfer rules. The constituent structure, the characterizing predicative triples and the derived features are combined to form a canonical form of the text portion. Each canonical form is added to the structural natural language index. A retrieved question is classified to determine question type and a corresponding canonical form for the question is generated. The entries in the structural natural language index are searched for entries matching the canonical form of the question and relevant to the question type. The characterizing predicative triples are used in conjunction with a generation grammar to create an answer. If the generation fails, some or all of the constituent structure of the matching entry is returned as the answer.

Ultrawide-band communication system and method

An impulse radio communications system using one or more subcarriers to communicate information from an impulse radio transmitter to an impulse radio receiver. The impulse radio communication system is an ultrawide-band time domain system. The use of subcarriers provides impulse radio transmissions added channelization, smoothing and fidelity. Subcarriers of different frequencies or waveforms can be used to add channelization of impulse radio signals. Thus, an impulse radio link can communicate many independent channels simultaneously by employing different subcarriers for each channel. The impulse radio uses modulated subcarrier(s) for time positioning a periodic timing signal or a coded timing signal. Alternatively, the coded timing signal can be summed or mixed with the modulated subcarrier(s) and the resultant signal is used to time modulate the periodic timing signal. Direct digital modulation of data is another form of subcarrier modulation for impulse radio signals. Direct digital modulation can be used alone to time modulate the periodic timing signal or the direct digitally modulated the periodic timing signal can be further modulated with one or more modulated subcarrier signals. Linearization of a time modulator permits the impulse radio transmitter and receiver to generate time delays having the necessary accuracy for impulse radio communications.

Residue-compensating A/D converter

An analog-to-digital converter system [50D] processing an input signal, g, which can be either a discrete-time or a continuous-time signal. A first quantizer [154] generates a first digital signal, d0(k), representing the sum of the input signal, g, and a dithering signal, y0. A digital-to-analog converter [156] generates an analog feedback signal, alpha, representing accurately the first digital signal, d0(k). The DAC [156] may be linearized by the use of mismatch-shaping techniques. A filter [158] generates the dithering signal, y0, by selectively amplifying in the signal band the residue signal, r0, defined as the difference of the input signal, g, and the analog feedback signal, alpha. Optional signal paths [166][168] are used to minimize the closed-loop signal transfer function from g to y0, which ideally will be zero. An analog compensation signal, m0, which is described by a well-controlled relationship to the residue signal, r0, is extracted from the filter [158]. Ideally, the closed-loop signal transfer function from g to m0 will be zero, or at least small in the signal band. A second quantizer [160] converts the analog compensation signal, m0, into a second digital signal, dm0(k). The two digital signals, d0(k) and dm0(k), are filtered individually and then added to form the overall output signal, dg(k). The second digital filter [164] has a low signal-band gain, which implies that the sensitivity to signal-band errors caused by the second quantizer [160] will be low. The output signal, dg(k), is a highly-accurate high-resolution representation of the input signal, g. Circuit imperfections, such as mismatch, gain errors, and nonlinearities, will cause only noise-like errors having a very low spectral power density in the signal band.The invention facilitates the implementation of uncalibrated highly-linear high-resolution wide-bandwidth A/D converters [50D], e.g., for use in digital communication systems, such as xDSL modems and other demanding consumer-market products for which low cost is of the essence.

Wideband enhanced digital injection predistortion system and method

A system for digitally linearizing the nonlinear behaviour of RF high efficiency amplifiers employing baseband predistortion techniques is disclosed. The system provides additive or multiplicative predistortion of the digital quadrature (I/Q) input signal in order to minimize distortion at the output of the amplifier. The predistorter uses a discrete-time polynomial kernel to model the inverse transfer characteristic of the amplifier, providing separate and simultaneous compensation for nonlinear static distortion, linear dynamic distortion and nonlinear dynamic effects including reactive electrical memory effects. Compensation for thermal memory effects also is embedded in the nonlinear dynamic compensation operation of the predistorter and is implemented parametrically using an autoregressive dynamics tracking mechanism. A predistortion controller periodically monitors the output of the amplifier and compares it to the quadrature input signal to compute estimates of the residual output distortion of the amplifier. Output distortion estimates are used to adaptively compute the values of the parameters of the predistorter in response to changes in the amplifier's operating conditions (temperature drifts, changes in modulation input bandwidth, variations in drive level, aging, etc). The predistortion parameter values computed by the predistortion controller are stored in non-volatile memory and used in the polynomial digital predistorter. The digital predistortion system of the invention may provide broadband linearization of highly nonlinear and highly efficient RF amplification circuits including, but not limited to, dynamic load modulation amplifiers.

Method and apparatus for amplifier linearization using adaptive predistortion

A signal processing method and apparatus capable of correcting signal distortion introduced by an RF power amplifier is disclosed, which includes the use of a buffer to store a plurality of samples representing at least a portion of an input signal intended for amplification by the RF power amplifier, the use of a self-receiver to receive an output signal generated by the RF power amplifier, the use of a synchronization unit to determine, as a matching input sample, which of the stored plurality of samples corresponds most closely to the output signal, and the use of a predistortion unit to selectively apply a distortion correction function to the input signal prior to amplification by the RF power amplifier in which the distortion correction function being derived from a relationship between the matching input sample and the output signal. This permits more precise and updateable determination of the delays involved in the RF modulation and amplification stages of the amplifier and the self-receiver, thus allowing for more precise and aggressive adaptive predistortion to be used. A phase offset correction is optionally provided to correct a phase offset in the realized sample of the output signal relative to the matching input symbol. Additionally, a sampling phase error correction unit may be provided to generate sampling alteration information to an analog-to-digital converter to cause such analog-to-digital converter to selectively alter sampling of the output signal.

Self-adaptive index time varying slip form posture control method of reentry flight vehicle

The invention relates to a self-adaptive index time varying slip form posture control method of a reentry flight vehicle, belonging to the technical field of flight vehicles. The method comprises the steps of firstly establishing a posture motion equation in a mode that a powerless reentry flight vehicle model is used as an object; secondly modifying the equation into the mode of an MIMO (Multiple Input Multiple Output) affine non-linear system, further applying a feedback linearization principle to carry out linearization processing so as to obtain a three-channel linearization model of pitching, rolling and yawing; aiming at the obtained linearization system, designing a modified self-adaptive index time varying slip form controller; and subsequently obtaining a control moment instruction for the posture control of the reentry flight vehicle, and inputting the control moment instruction into the reentry flight vehicle so as to control the posture. By combining the index time varying slip form control with a self-adaptive method, the problem of excessive adaptation of switch gain in the self-adaptive slip form control is solved to a certain extent, the uncertainty of system parameters and the influence of external disturbance can be suppressed effectively, and the precise posture control is realized.
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