62 results about "Nonlinear transfer function" patented technology

The present invention provides an advanced adaptive predistortion linearization technique to dramatically reduce nonlinear distortion in power amplifiers over a very wide instantaneous bandwidth (up to 2 GHz) and over a wide range of amplifier types, input frequencies, signal types, amplitudes, temperature, and other environmental and signal conditions. In an embodiment of the invention, the predistortion linearization circuitry comprises (1) a higher-order polynomial model of an amplifier's gain and phase characteristics—higher than a third-order polynomial model; (2) an adaptive calibration technique; and (3) a heuristic calibration technique. The higher-order polynomial model is generated by introducing, for example, a plurality of multi-tone test signals with varying center frequency and spacing into the power amplifier. From the power amplifier's corresponding output, the nonlinearities are modeled by employing a higher-order curve fit to capture the irregularities in the nonlinear transfer function. Different distortion transfer functions can be implemented for different operating conditions. The adaptive calibration technique is based on a feedback analysis technique, which updates the applicable distortion transfer function by analyzing the error signal between the introduced input signal and the output signal in real-time. The heuristic calibration technique implements different distortion transfer functions based on historical operating conditions and optimal configurations of the power amplifier.

A transfer function generator provides the ability to provide a non-linear response in a feedback loop to compensate for non-linearities introduced elsewhere in the system. The transfer function generator includes a non-linear function generator configured to provide an output current that is a non-linear function of an input signal representing an error to be corrected. The transfer function generator can also include a linear function generator configure to provide a linear output current as a function of an input current representing the error corrected. Tuning devices can be provided to adjust the turn-on level of the non-linear function generator and the output level of the linear function generator to allow the transfer function generator flexibility in implementation.

A system that manages a supplemental energy source connected to a power grid uses a two stage control strategy to manage power transfers in and out of the power grid as well as in and out of an energy storage system, such as a battery bank. One stage uses a non-linear transfer function to control an output frequency of a DC-to-AC inverter to limit undesired effects of power transients that occur on the grid. A second stage uses control strategy for transferring energy between the energy storage system and an internal DC link based on a relationship between a voltage on a DC link connecting the first and second stages and a DC link reference voltage, the voltage on the DC link, and a voltage at the energy storage system. The control strategy includes rapid charging, over-charging protection, and grid transient stabilization.

The present invention provides an advanced adaptive predistortion linearization technique to dramatically reduce nonlinear distortion in power amplifiers over a very wide instantaneous bandwidth (up to 2 GHz) and over a wide range of amplifier types, input frequencies, signal types, amplitudes, temperature, and other environmental and signal conditions. In an embodiment of the invention, the predistortion linearization circuitry comprises (1) a higher-order polynomial model of an amplifier's gain and phase characteristics—higher than a third-order polynomial model; (2) an adaptive calibration technique; and (3) a heuristic calibration technique. The higher-order polynomial model is generated by introducing, for example, a plurality of multi-tone test signals with varying center frequency and spacing into the power amplifier. From the power amplifier's corresponding output, the nonlinearities are modeled by employing a higher-order curve fit to capture the irregularities in the nonlinear transfer function. Different distortion transfer functions can be implemented for different operating conditions. The adaptive calibration technique is based on a feedback analysis technique, which updates the applicable distortion transfer function by analyzing the error signal between the introduced input signal and the output signal in real-time. The heuristic calibration technique implements different distortion transfer functions based on historical operating conditions and optimal configurations of the power amplifier.

The present invention provides an advanced adaptive predistortion linearization technique to dramatically reduce nonlinear distortion in power amplifiers over a very wide instantaneous bandwidth (up to 2 GHz) and over a wide range of amplifier types, input frequencies, signal types, amplitudes, temperature, and other environmental and signal conditions. In an embodiment of the invention, the predistortion linearization circuitry comprises (1) a higher-order polynomial model of an amplifier's gain and phase characteristics—higher than a third-order polynomial model; (2) an adaptive calibration technique; and (3) a heuristic calibration technique. The higher-order polynomial model is generated by introducing, for example, a plurality of multi-tone test signals with varying center frequency and spacing into the power amplifier. From the power amplifier's corresponding output, the nonlinearities are modeled by employing a higher-order curve fit to capture the irregularities in the nonlinear transfer function. Different distortion transfer functions can be implemented for different operating conditions. The adaptive calibration technique is based on a feedback analysis technique, which updates the applicable distortion transfer function by analyzing the error signal between the introduced input signal and the output signal in real-time. The heuristic calibration technique implements different distortion transfer functions based on historical operating conditions and optimal configurations of the power amplifier.

Signal amplifiers having a non-linear transfer function. A high speed (high bandwidth) circuit with a non-linear transfer function over a limited range of input signal is provided. By appropriate choice of components, the non-linear transfer function can be used to accurately approximate any monotonic function such as a square root transfer function. In another aspect, a piecewise non-linear circuit arrangement using a set of non-linear sub-circuits is provided to accurately generate a desired non-linear transfer function over an extended dynamic range of input signal. In one implementation of such a circuit, each of the sub-circuits approximates the desired non-linear function over a portion of the input range.

The invention discloses an RBF dual neural network adaptive sliding mode control method for an active power filter. The method is characterized by comprising the following steps: step (1), establishing a mathematical model of the active power filter; (2) designing an adaptive RBF dual neural network based on a fractional order sliding mode surface, and separately approximating the nonlinear function and the upper bound of interference of the system by using the two RBF neural networks; and step (3) controlling the active power filter according to a fractional order RBF dual neural network sliding mode controller. According to the method disclosed by the invention, the characteristics that the fractional order can get rid of the dependence of system functions and improve the control response of the system are adopted; on this basis, the nonlinear function and the upper bound of interference values of the system can be approximated by adopting the characteristic that the RBF neural networks do not relay on the model of the system; and moreover, the stability of a system controller can be proved by designing the Lyapunov function, the real-time tracking compensation can be performed for the instruction current, and high reliability, high robustness to parameter variation and high stability can be achieved.

The invention discloses an image enhancement method under ambient light, and belongs to the field of image processing. The image enhancement method comprises the steps that the brightness value of an original image is extracted, a visibility threshold is determined, and a brightness enhanced image is determined through combination of light intensity of the environment in which display equipment is arranged. The gradient gain function of a display image is determined through combination of a just-noticeable-distortion model according to the light intensity of the environment in which the display equipment is arranged so that the enhanced display image under ambient light is acquired through a weighed optimization mode. A readability enhanced color display image is obtained through color spatial conversion. The brightness and the details of the display image are enhanced through a gradient domain optimization framework based on weighting so that readability of the display image under ambient light can be enhanced, the brightness of the display image is enhanced by using a nonlinear transfer function under ambient light, gradient loss caused by ambient light can be compensated by adopting the just-noticeable-distortion model, and finally readability of the image on the display equipment can be enhanced.

A system and method of performing aeroelastic analysis using a neural network. Input parameters, such as mass and location, contributing to aeroelastic characterization are determined and constrained. A model of a structure to be analyzed can be constructed. The model can include a number of locations where the input parameters can be varied. The aeroelastic characteristic of the structure can be analyzed using a finite element model to determine a number of output characteristics, each of which can correspond to at least one of a plurality of input samples. A neural network can be generated for determining the aeroelastic characteristic based on input parameters. The input sample / output characteristic pairs can be used to train the neural network. The weights and bias values from the trained neural network can be used to generate a non-linear transfer function that generates the aeroelastic characteristic in response to input parameters.

A method is provided for equalization of nonlinear distortion in a distorted signal comprising the steps of: digitizing the distorted signal and passing the digitized distorted signal through an inverse non-linear transfer function to equalize the nonlinear distortion. Other systems and methods are disclosed.

A communication system includes an encryptor and a decryptor. For improved encryption security, the encryptor includes a multitap delay line to produce mutually delayed samples of the signal to be encrypted. Each sample is operated on by a key or function to produce modified signal samples, and the modified signal samples are summed or combined to produce the encrypted signal. According to one aspect of the invention, at least one of the keys or functions includes a nonlinear function. In some embodiments, the functions are time-variant for improved security. Decryption is accomplished in some embodiments by an equalizer. The preferred equalizer is the maximum-likelihood-sequence estimators matched to the encryption functions. A Viterbi algorithm makes it easy to implement the matched equalizer.

Aiming at the difficulty and inaccuracy of parameter identification of nonlinear model, this invention proposes an identification algorithm based on improved differential evolution algorithm. By establishing a lifetime mechanism, the scaling factor and crossover rate can be adjusted dynamically according to the lifetime value, so as to avoid premature convergence at the beginning of the algorithmand retain high-quality solution at the later stage, so as to accelerate the convergence rate. In order to verify the performance and practicability of the improved algorithm, the typical test functions are used to compare and test, and the nonlinear transfer function model and Hammerstein model are identified. The experimental results show that the improved algorithm has fast convergence speed and high identification accuracy, and it is effective and feasible for parameter identification of nonlinear system.

The invention discloses a dual-active-bridge resonant convert modeling, ord reduction, design method, device and system. Under the condition of controlling the output voltage of resonant double activebridge converter by single phase-shifting control method, by using the transmission power formula of resonant double active bridge converter, the order of resonant elements in resonant double activebridge converter is reduced, and the average value equivalent model is established. Based on the average mode equivalence, the small signal model of the resonant double active bridge converter is established by using small signal method, and the transfer function is obtained according to the control quantity and the control object. the zero-pole distribution of the transfer function is analyzed and the order of the transfer function is reduced; Aiming at the reduced-order transfer function, the controller parameter design method is used to design the typical type II system. The invention has the advantages of simple principle and clear organization, provides the theoretical basis for the analysis of the resonant double active bridge converter, reduces the difficulty of analysis and design,and is easy to adopt the traditional control system parameter design scheme to design the controller.

A system and method of performing aeroelastic analysis using a neural network. Input parameters, such as mass and location, contributing to aeroelastic characterization are determined and constrained. A model of a structure to be analyzed can be constructed. The model can include a number of locations where the input parameters can be varied. The aeroelastic characteristic of the structure can be analyzed using a finite element model to determine a number of output characteristics, each of which can correspond to at least one of a plurality of input samples. A neural network can be generated for determining the aeroelastic characteristic based on input parameters. The input sample / output characteristic pairs can be used to train the neural network. The weights and bias values from the trained neural network can be used to generate a non-linear transfer function that generates the aeroelastic characteristic in response to input parameters.

The invention discloses a nonlinear effect modeling method for a radio frequency coaxial connector. The method comprises: a structure and material characteristics of a connector are determined by electron microscope scanning and an energy spectrum analysis method, so that a qualitative analysis of a nonlinear effect is realized; voltage-current curve testing is carried out by using a microhm microvoltmeter to realize a quantitative test analysis of a nonlinear effect under the direct current of the connector; with a passive intermodulation tester, a third-order intermodulation power is testedso as to realize a quantitative test analysis of the nonlinear effect under the high frequency of the connector; and on the basis of a tunnel effect, a skin effect, and a high-frequency electrical contact theory, a nonlinear contact resistor model, a high-frequency equivalent circuit model and a nonlinear transfer function are established to realize the theoretical analysis of the nonlinear effectof the connector. According to the invention, on the basis of combination of experimental testing and theoretical modeling, the nonlinear effect of the connector is analyzed comprehensively from thequalitative and quantitative perspectives. The method is suitable for the nonlinear effect analyses of coaxial connectors in all communication systems.

A gamma correction circuit for correcting a digital video signal, the circuit comprising first (6) and second (8) lookup tables for storing discrete output intensity data and the associated slope data of a non-linear transfer function, respectively, for each of the discrete input video signal intensities, an adder (10) having a first input connected to the output of the first lookup table, a multiplier (12) having a first input connected to the output of the second look-up table (8), characterized by a quantizer (4) for providing the most significant bits of the incoming video signal to address the first (6) and second (8) lookup tables and to transfer the corresponding output intensity data to the adder (10) and the associated slope data to the multiplier (12), the quantizer (4) transmitting the remaining least significant bits of the input video signal to the second input of the multiplier (12), the multiplier (12) multiplying the slope data with the remaining least significant bits and feeding the multiplication result to the second input of the adder (10), the adder (10) adding the output intensity data and the multiplication result to generate a corrected video signal.

A gamma correction circuit for correcting a digital video signal, the circuit comprising first (6) and second (8) lookup tables for storing discrete output intensity data and the associated slope data of a non-linear transfer function, respectively, for each of the discrete input video signal intensities, an adder (10) having a first input connected to the output of the first lookup table, a multiplier (12) having a first input connected to the output of the second look-up table (8), characterized by a quantizer (4) for providing the most significant bits of the incoming video signal to address the first (6) and second (8) lookup tables and to transfer the corresponding output intensity data to the adder (10) and the associated slope data to the multiplier (12), the quantizer (4) transmitting the remaining least significant bits of the input video signal to the second input of the multiplier (12), the multiplier (12) multiplying the slope data with the remaining least significant bits and feeding the multiplication result to the second input of the adder (10), the adder (10) adding the output intensity data and the multiplication result to generate a corrected video signal.

One embodiment of the present invention sets forth a technique for correcting color values. The technique includes downsampling first color space values to generate downsampled color space values and upsampling the downsampled color space values to generate second color space values. The technique further includes modifying at least one component value included in the downsampled color space values based on a first component value included in the first color space values, a second component value included in the second color space values, and an approximation of a nonlinear transfer function.

PLL circuit for eliminating self-jitter in a signal which is received by a control circuit, having a phase comparison circuit for producing a phase difference signal, which indicates the phase difference between the received signal and a fed-back output signal from the PLL circuit; having a loop filter for filtering the phase difference signal which is produced; having an oscillator, which is controlled by the filtered phase difference signal, for producing the output signal from the PLL circuit; with the loop filter having a nonlinear transfer function.

Embodiments are provided to improve direct detection for optical transmissions. In an embodiment, a method by a transmitter includes adjusting, using a nonlinear equalizer (NLE), a drive voltage for an optical modulator in accordance with a mapping between the drive voltage and an output of the optical modulator. The mapping is an inverse function of a nonlinear transfer function at the optical modulator between the output and to the drive voltage. The method further includes driving, using the adjusted drive voltage, the output of the optical modulator. The output is a single-side band (SSB) signal and is sufficiently linear with respect to the drive voltage for allowing direct detection at a receiver.

A pixel pre-processing comprises obtaining an original linear luminance component value of a pixel in a picture in a third color space determined based on a linear color of the pixel in a first color space. A non-linear luma component value in a second color space is derived for the pixel based on a first non-linear chroma component value in the second color space, a second non-linear chroma component value in the second color space and the original linear luminance component value in the third color space. The pre-processing reduces luminance artifacts that otherwise may occur when chroma subsampling is used in combination with a non-linear transfer function.

Methods and systems for analyzing flutter test data using non-linear transfer function frequency response fitting are provided. In one embodiment, a plurality of data points are read, with each data point representing a motion of an aeroelastic structure (e.g. an aircraft surface) at a different location. A closed form fit to the plurality of data points is performed to obtain an initial curve fit condition. At least one non-linear transfer function frequency response curve fit is then performed to the plurality of data points.

A method of characterizing an envelope tracking amplification stage, the method comprising: generating an input test waveform which is representative of an input waveform under normal operating conditions of the amplification stage; applying a respective one of a plurality of different shaping functions, each comprising a non-linear transfer function, to the input signal envelope in each of a plurality of test periods during the period in which the input test waveform is applied as the input signal to generate the input to the envelope tracking modulated supply voltage; measuring parameters of the amplification stage during the period in which the input test waveform is applied in order to allow determination of the gain, phase and efficiency characteristics of the amplifier; and for each of the gain, phase and efficiency characteristics, generating a three dimensional plot of the characteristic with respect to input power and supply voltage applied to the amplifier.

One embodiment of the present invention sets forth a technique for correcting color values. The technique includes downsampling first color space values to generate downsampled color space values and upsampling the downsampled color space values via a first upsampling filter type to generate second color space values. The technique further includes modifying at least one component value included in the downsampled color space values based on a first component value included in the first color space values, a second component value included in the second color space values, and an approximation of a nonlinear transfer function. The technique further includes at least one of (i) storing an indication of the first upsampling filter type in conjunction with a video bitstream associated with the at least one component value, and (ii) transmitting the indication of the first upsampling filter type to a receiving device in conjunction with the video bitstream.

Nonlinear elastography systems and methods are provided. The elastography system includes a data acquisition module, such as an imaging device, and associated system control circuitry. The data acquisition module is configured to acquire various data, such as displacement and / or force data, from a material. A nonlinear transfer function is applied to the acquired data to generate information about the material's stiffness. In one implementation, a map representative of the material's stiffness is generated.