272 results about "Non linear response" patented technology

A method of multivariate spectral analysis, termed augmented classical least squares (ACLS), provides an improved CLS calibration model when unmodeled sources of spectral variation are contained in a calibration sample set. The ACLS methods use information derived from component or spectral residuals during the CLS calibration to provide an improved calibration-augmented CLS model. The ACLS methods are based on CLS so that they retain the qualitative benefits of CLS, yet they have the flexibility of PLS and other hybrid techniques in that they can define a prediction model even with unmodeled sources of spectral variation that are not explicitly included in the calibration model. The unmodeled sources of spectral variation may be unknown constituents, constituents with unknown concentrations, nonlinear responses, non-uniform and correlated errors, or other sources of spectral variation that are present in the calibration sample spectra. Also, since the various ACLS methods are based on CLS, they can incorporate the new prediction-augmented CLS (PACLS) method of updating the prediction model for new sources of spectral variation contained in the prediction sample set without having to return to the calibration process. The ACLS methods can also be applied to alternating least squares models. The ACLS methods can be applied to all types of multivariate data.

An improved method of sensing strain allows measurements of stress, torque, vibration and other loads imposed on a body without physical contact between the body/sensor and the monitoring equipment. An induction loop is at least partially comprised of a magnetostrictive material with a non-linear current-voltage relationship. An excitation device such as a coil is used to induce an AC response in the sensor. The non-linear response to the induced current is received by a sensing device such as a sensing coil, and the output thereof is filtered. The excitation device and sensing device are located in operative proximity to the sensor, but need not be in contact therewith, allowing easy measurement in small spaces, under harsh conditions, or of moving bodies such as drive shafts. The non-linear response of the sensor induces easily detectable harmonics of the base frequency of excitation. These harmonics may advantageously be measured as well.

A method for detecting electrical arcing in a plasma process powered by an AC source comprises the steps of sampling at least one Fourier component of the AC source waveform distorted by the non-linear response of the plasma, determining when a change in amplitude of the component, irrespective of the direction of the change, exceeds any one of a plurality of different threshold levels, and determining the duration that each such threshold is exceeded. Each threshold is a predetermined fraction of a running average of the amplitude of the component.

A transmission circuit includes: a modulated signal generator; a modulated signal line where an OFDM modulated wave flows; a detector; a phase component line for transmitting a phase component; an amplitude component line for transmitting an amplitude component; a level judging circuit for judging the level of the amplitude component; a constant-voltage supply line; first and second selectors; a quadrature converter; and an RF power amplifier. An EER or pseudo-EER technique is performed in a region where the RF input-output characteristic of the RF power amplifier with an EER technique exhibits a linear response, whereas usual modulation is performed in a region where a nonlinear response is exhibited. The modulation method is switched using the level judging circuit and the selectors with reference to a threshold value which is the boundary between the region where the linear response is exhibited and the region where the nonlinear response is exhibited.

The invention relates to a radar system which comprises: (a) at least two transmitting units for simultaneously, and in synchronization transmitting electromagnetic radiation in distinct frequencies f₁, f₂, f₃ . . . towards a space of interest; and (b) at least one receiving unit tuned to a frequency of nf₁+mf₂+qf₃ . . . , wherein n, m, q . . . being integers not equal to zero, for receiving a non-linear response of said radiation from objects located within the said space of interest.

An embodiment of the invention is a time-delay invariant predistortion approach to linearize power amplifiers in wireless RF transmitters. The predistortion architecture is based on the stored-compensation or memory-compensation principle by using a combined time-delay addressing method, and therefore, the architecture has an intrinsic, self-calibrating time-delay compensation function. The predistortion architecture only uses a lookup table to conduct both the correction of non-linear responses of a power amplifier and the compensation of any time-delay effects presented in the same system. Due to the time-delay invariant characteristic, the predistortion design has a wider dynamic range processing advantage for wireless RF signals, and therefore can be implemented in multi-carrier and multi-channel wireless systems.

Circuits and methods are disclosed for compensating for received signal distortion caused by non-linearittes in wideband receivers. An exemplary receiver includes a distortion waveform generator (106) configured to approximate non-linear response characteristics of a downconverter circuit (104a-b, 105) used to downconvert the received radio frequency signal. The resulting estimated distortion waveform is filtered, using filter(s) (107c) substantially similar to those used for filtering an intermediate frequency signal that includes the desired signal and non-linear distortion products caused by strong interfering signals. The filtered estimated distortion waveform and intermediate frequency signal are sampled, to obtain a sampled distortion signal and a sampled signal of interest. The sampled distortion signal and the sampled signal of interest are divided into a plurality of frequency channels. For a selected number of frequency channels, the sampled distortion signal for a frequency channel is scaled, and subtracted from the corresponding sampled signal of interest for the same frequency channel to obtain reduced-interference signal samples for the frequency channel.

This invention relates to Analog to Digital Converters (ADC) and, inter alia, to Time Interleaved ADCs and Successive Approximation Register (SAR) ADC's. In a conventional Time Interleaved ADC employing SAR ADC units, the input signal is processed through a track-and-hold circuit (T/H), and then through a buffer circuit, before the SAR ADC unit. There, by means of a comparator, the signal is compared with a Digital-to-Analog Converter (DAC) signal from the SAR logic. The buffer reduces the influence of capacitive loading and physical layout design on the SAR ADC input, but typically has a non-linear response and thus introduces distortion to the input signal. This can limit the ADC linearity, particularly for high-speed ADCs operating with low-supply voltages. An objective of the invention is to reduce or eliminate the effect of the buffer non-linearity. This is done in some embodiments by routing both the signals to the comparator through the same buffer circuit. In another embodiment the DAC signal is routed through a separate second buffer circuit. By use of a single buffer circuit, or where there is ideal matching of the buffer circuits in the latter embodiment, the distortion effects are completely eliminated; however, for practical imperfectly matched buffer circuits according to the latter embodiment, the gain and off-set mismatches can be accommodated through calibration of the buffers or, in suitable applications, through the DAC calibration.

A nonlinear metasurface structure including a multi-quantum-well layer designed for a nonlinear response for a desired nonlinear optical process and an array of nanoantennas coupled to the intersubband transitions of the multi-quantum-well layer. Each nanoantenna in the array is designed to have electromagnetic resonances at or close to all input and output frequencies of a given nonlinear optical process. Nanoantennas allow efficient coupling of any incident and outgoing light polarizations to intersubband transitions. Nanoantennas may further provide significant field enhancement in the multi-quantum-well layer. As a result, the nonlinear metasurface structure can be designed to produce a highly nonlinear response for any polarization and angle of incidence of incoming and outgoing waves in a nonlinear optical process. Due to their very larger nonlinear response, efficient frequency conversion can be produced in these metasurfaces without the stringent phase-matching constraints of bulk nonlinear crystals.

The invention discloses a self-adaptation optical system near-field wave-front sensor calibration device and a calibration method based on a phase-diversity method. The self-adaptation optical system near-field wave-front sensor calibration device consists of a wave-front corrector, a spectroscope, a near-field wave-front sensor, a wave-front controller, an imaging system and a phase-diversity wave-front sensor. According to the method, the phase-diversity wave-front sensor is used for measuring the static aberration of the whole system, and the wave-front controller is used for controlling the wave-front corrector to correct the static aberration; and after the static aberration is corrected, the zero point at the reference position of the near-field wave-front sensor at the pupil plane position is calibrated or the zero point of the absolute aberration is set, and the two zero points are used as the wave-front control objective of the self-adaptation optical system to effectively correct the static aberration of the whole optical path. According to the self-adaptation optical system near-field wave-front sensor calibration device and the calibration method, the static aberration of the whole optical path can be effectively corrected, the wave-front control error caused by the non-linear response of the corrector can be avoided, and the correction capability of the self-adaptation optical system can be improved obviously without obviously increasing the system complexity and the additional aberration.

A method and circuit for measuring the optical modulation amplitude in the operating region of a laser diode is described. The method utilises two measurements of OMA, each measurement being related to the slope in a specific portion of the operating region of the power/current characteristic curve of the laser diode. By combining the two measurement values, the invention provides a 1 measurement for OMA in the operating region of the laser diode that allows for the presence of a non-linear response in the region.

A method and apparatus in an ultrasound imaging system is disclosed that enhances the contrast-to-tissue ratio and signal-to-noise ratio of contrast imaging using stepped-chirp waveforms. The first waveform component is employed with a first frequency optimized to initiate the bubble dynamics and the second waveform component is employed with a second frequency optimized to produce an enhanced bubble nonlinear response. The first waveform component and the at least a second waveform component are transmitted as a single stepped-chirp transmit pulse. At least one of a center frequency, an amplitude, a starting phase, and a bandwidth of the waveform components are adjusted to generate the single stepped-chirp transmit pulse. A relative phase, a switch time, and a time delay between the waveform components are also adjusted for maximal enhancement of bubble nonlinear response.