4514 results about "Non linearity" patented technology

A two-stage structure for performing non-linear echo cancellation is described in which a first echo canceller is used to attenuate linear echo components of a microphone signal and a second echo canceller is used to attenuate non-linear echo components of the output signal generated by the first echo canceller. One or both of the echo cancellers may be implemented using closed-form solutions, including a closed form solution for a hybrid method in the frequency domain.

Ringing artifacts are removed from a quantized image by an image de-ringing filter that includes a determination unit, an adaptive filter and a nonlinear low-pass filter. The determination unit determines whether each selected pixel of a first set of selected pixels of an image contains a ringing artifact based on, for example, gray-level values of selected pixels within a determination kernel of pixels relating to the selected pixel. The adaptive filter generates a filtered gray-level value for each pixel determined by the determination unit to contain a ringing artifact based on, for example, gray-level values of selected pixels within a filtering kernel of pixels relating to the pixel. The nonlinear low-pass filter generates a low-pass-filtered gray-level value for each selected pixel of a second set of selected pixels of the image.

The present invention includes methods and devices to apply predistortion to correct nonlinearities of a power amplifier in an OFDM symbol transmission system. More particularly, predistortion is patterned to take into account clipping of symbols and to match an effective input range of the predistorter with an average power output of the power amplifier. This invention may be applied to a variety of standards utilizing OFDM technology, including IEEE 802.11a, Hiperlan/2 and MMAC.

A method for capturing a digital panoramic image includes projecting a panorama onto an image sensor by means of a panoramic objective lens. The panoramic objective lens has a distribution function of the image points that is not linear relative to the field angle of the object points of the panorama, such that at least one zone of the image obtained is expanded while at least another zone of the image is compressed. When a panoramic image obtained is then displayed, correcting the non-linearity of the initial image is required and is performed by means of a reciprocal function of the non-linear distribution function of the objective lens or by means of the non-linear distribution function.

A re-writable memory that uses resistive memory cell elements with non-linear IV characteristics is disclosed. Non-linearity is important in certain memory arrays to prevent unselected cells from being disturbed and to reduce the required current. Non-linearity refers to the ability of the element to block the majority of current up to a certain level, but then, once that level is reached, the element allows the majority of the current over and above that level to flow.

Circuits that are matched to balanced codes may recover transmitted information in a noise resilient and power efficient manner. Circuit components for processing a balanced code may include one or more of: matched amplification of the signals representing the balanced code, matched equalization and/or filtering on the signals representing the balanced code, matched non-linear filtering on the signaling representing the balanced code to detect the presence of particular symbols and matched latching of the signals representing the balanced code. Such matched circuits and circuit components may be achieved at least in part by incorporating suitable common circuit nodes and/or a single energy source into circuit topologies.

A method and system for full-field fringe-projection for 3-D surface-geometry measurement, referred to as “triangular-pattern phase-shifting” is disclosed. A triangular grey-scale-level-coded fringe pattern is computer generated, projected along a first direction onto an object or scene surface and distorted according to the surface geometry. The 3-D coordinates of points on the surface are calculated by triangulation from distorted triangular fringe-pattern images acquired by a CCD camera along a second direction and a triangular-shape intensity-ratio distribution is obtained from calculation of the captured distorted triangular fringe-pattern images. Removal of the triangular shape of the intensity ratio over each pattern pitch generates a wrapped intensity-ratio distribution obtained by removing the discontinuity of the wrapped image with a modified unwrapping method. Intensity ratio-to-height conversion is used to reconstruct the 3-D surface coordinates of the object. Intensity-ratio error compensation involves estimating intensity-ratio error in a simulation of the measurement process with both real and ideal captured triangular-pattern images obtained from real and ideal gamma non-linearity functions. A look-up table relating the measure intensity-ratio to the corresponding intensity-ratio error is constructed and used for intensity-ratio error compensation. The inventive system is based on two-step phase-shifting but can be extended for multiple-step phase-shifting.

The present invention includes a method and system for determining the profile of a structure in an integrated circuit from a measured signal, the signal measured off the structure with a metrology device, selecting a best match of the measured signal in a profile data space, the profile data space having data points with a specified extent of non-linearity, and performing a refinement procedure to determine refined profile parameters. One embodiment includes a refinement procedure comprising finding a polyhedron in a function domain of cost functions of the profile library signals and profile parameters and minimizing the total cost function using the weighted average method. Other embodiments include profile parameter refinement procedures using sensitivity analysis, a clustering approach, regression-based methods, localized fine-resolution refinement library method, iterative library refinement method, and other cost optimization or refinement algorithms, procedures, and methods. Refinement of profile parameters may be invoked automatically or invoked based on predetermined criteria such as exceeding an error metric between the measured signal versus the best match profile library.

A RF-digital hybrid mode power amplifier system for achieving high efficiency and high linearity in wideband communication systems is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier in the RF domain. The power amplifier characteristics such as variation of linearity and asymmetric distortion of the amplifier output signal are monitored by the narrowband feedback path and controlled by the adaptation algorithm in a digital module. Therefore, the present invention could compensate the nonlinearities as well as memory effects of the power amplifier systems and also improve performances, in terms of power added efficiency, adjacent channel leakage ratio and peak-to-average power ratio. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers and multi-channels. As a result, the digital hybrid mode power amplifier system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems, where baseband I-Q signal information is not readily available.

An advanced adaptive baseband/RF predistorting device, which advantageously uses the concept of digital receiver technology into power amplifier (PA) linearization area. The predistorting device performs an instantaneous characterization of the PA using two digital receivers to supply its dynamic AM-AM and AM-PM transfer functions used to synthesize Look-Up Tables (LUT) which implement the complex predistortion function in order to compensate for any non-linearity and memory effects.

A multimode optical fibre communications system, and in particular to a system in which non-linearities in the propagation of the signal through a multimode optical communications channel degrade the signal presented to the receiver. The system includes an optical transmitter unit for connection to a multimode optical fibre transmission link. The transmitter unit has a data input for receiving an input data signal, a data signal processing circuit and a source of optical radiation. The data signal processing circuit is arranged to receive the input data signal from the data input and to provide a processed data signal to the source of optical radiation and the source of optical radiation is arranged to generate from this an optical signal for transmission by a multimode optical fibre. The data processing circuit is arranged to provide from the input data signal a non-inverted data signal and an inverted data signal, receive a control signal for controlling the generation of the processed data signal, apply a controllable delay in accordance with the control signal to at least one of the non-inverted and inverted data signals, and combine the non-inverted and inverted signals after the application of the controllable delay(s) and gain factor(s) to generate the processed data signal.

A power amplifier (PA) provides dynamic stability and gain control for linear and non-linear operation. The PA operates with a baseband processor and a transmitter, in which the PA receives a signal from the transmitter for power amplification prior to transmission of the signal. The PA is configured to select between the linear mode of operation and the non-linear mode of operation, in which device scaling within the PA is achieved by changing a device sizing of at least one stage of the PA. Further to changing the device size, the PA changes biasing resistance and impedance of a matching network in response to the changing of the device size to control power output and stability for the PA.

A transmitter for an optical transmission system transmits an optical sub carrier multiplexed signal comprising number of sub-carriers, onto an optical transmission path, and provides spectral shaping by different magnitudes of the sub-carriers, or different modulation formats for different sub carriers. This spectral shaping can reduce performance degradation by Kerr effect optical non linearities. This can mean higher input powers may be launched. The magnitudes can provide a signal spectrum which is lower near a centre of a band of sub carriers than near an edge of the band. Such spectral shaping can be provided in the receiver either to undo the pre emphasis in the transmitter, or to reduce non linearities from components at the receiving side.

A circuit and method measure the output voltage of a CMOS pixel in a manner that substantially reduces all columnar pattern noise due to mismatches in the signal processing circuits including the correlated double sampling amplifiers and A/D converters. The circuit includes a test switch, operatively connected between a reference voltage source and a correlated double sampling amplifier, for applying a test voltage from the reference voltage source when the state of the test switch is ON to the correlated double sampling amplifier. The reference voltage source produces a voltage corresponding to a full-scale voltage level to enable the determination of a gain error in the correlated double sampling amplifier and/or A/D converter; a voltage corresponding to ground to enable the determination of an offset error in the correlated double sampling amplifier and/or A/D converter; and a plurality of analog voltages ranging from analog ground to a full-scale voltage level to enable the determination of non-linearity errors in the A/D converter.

A method for determining a degree of acoustic non-linearity of an earth formation from seismic signals transmitted into the formation from within one wellbore and received from the formation in another wellbore. The seismic signals include two selected discrete frequencies. The method includes spectrally analyzing the received signals, determining from the spectral analysis the presence of a frequency representing a sum of the two selected frequencies, and determining a relative amplitude of the sum frequency with respect to the amplitudes of the two selected discrete frequencies. In a particular embodiment, the method includes determining the presence of a frequency in the spectrally analyzed signals representing the difference between the selected discrete frequencies, and determining the presence of harmonic multiples of one of the two selected discrete frequencies.

Nonlinearity-induced signal distortions are compensated by processing an input communications signal, in the electrical domain prior to Electrical-to-optical conversion and transmission through an optical link of a communications system. According to the invention, a compensation operator is determined that substantially mitigates the nonlinearity-induced signal distortions imparted to an optical signal traversing the communications system. The input communications signal is then input to the compensation operator to generate a predistorted electrical signal. This predistorted electrical signal is then used to modulate an optical source to generate a corresponding predistorted optical signal for transmission through the optical communications system. With this arrangement, arbitrary nonlinearity-induced signal distortions imparted by the optical link can be compensated in such a manner that a comparatively undistorted optical signal is obtained at the receiving end of the optical link.

The combination of filters and switches is used to solve the non-linearity problems in GSM/W-CDMA transceiver front-end wherein one common antenna is used for both the GSM mode and the W-CDMA mode. In particular, separate Rx/Tx paths and switches in the Rx paths are used to provide cross-band isolation between bands. All of the switches in the transceiver are disposed after the filters in that no switches are disposed between the filters and the antenna. Furthermore, bandpass filters are matched to one common node even if they are only disconnected at the output as long as the impedance at the output can be controlled.

Systems and methods are disclosed, especially designed for very compact hardware implementations, to generate random number strings with a high level of entropy at maximum speed. For immediate deployment of software implementations, certain permutations have been introduced to maintain the same level of unpredictability which is more amenable to hi-level software programming, with a small time loss on hardware execution; typically when hardware devices communicate with software implementations. Particular attention has been paid to maintain maximum correlation immunity, and to maximize non-linearity of the output sequence. Good stream ciphers are based on random generators which have a large number of secured internal binary variables, which lead to the page synchronized stream ciphering. The method for parsed page synchronization which is presented is especially valuable for Internet applications, where occasionally frame sequences are often mixed. The large number of internal variables with fast diffusion of individual bits wherein the masked message is fed back into the machine variables is potentially ideal for message authentication procedures.