192 results about "Phase error compensation" patented technology

Methods of compensating for radial incoherence in servo information that is read from adjacent servo tracks that have a phase offset relative to one another on a data storage disk of a disk drive are provided. While a transducer is seeking to a target track, the transducer generate a servo information signal that has a first component from servo information read from a first servo track on the disk and a second component from servo information read from a second servo track that is radially adjacent to the first servo track. The servo information in the first and second servo tracks are offset by a non-zero phase error relative to one another and are in a same servo sector on the disk. The servo information signal is sampled to generate a series of sampled servo values. A phase error of a group of the sampled servo values is determined. The sampled servo values are compensated in response to the determined phase error to generate compensated servo values with at least reduced phase error.

A receiver for a resonance signal of a magnetic resonance imaging system generates a baseband signal for image processing by dividing a raw resonance signal among multiple parallel channels, each amplified at a respective gain. A digital channel selector determines, at any given moment, a lowest-distortion channel to be further processed. Amplitude and phase error compensation are handled digitally using complex multipliers, which are derived by a calibration, based on a simple Larmor oscillator, which can be done without the need for a sample and without repeating when measurement conditions are changed. One of the important benefits of the invention is that it provides for gain selection without repeated calibration steps. This is particularly important in systems that employ fast imaging techniques such as fast spin echo, where the invention can speed imaging substantially.

The invention discloses a phase error compensation method applied to grating three-dimensional projection measurement. The method includes the following steps: generating sine grating stripes; collecting grating stripes that are modulated by the surface of an object; pre-processing images; carrying out phase unwrapping through a phase shift method on the basis of the pre-processed stripe images; projecting a grey-scale image with a single gray value onto the surface of a standard white board; mapping regional results in the step (5) onto a target surface of a projector through an obtained ideal phase; establishing regional correction models for different regions according to the regional results; projecting the sine grating stripes onto the object; solving an initial phase through a phaseshift method, compensating the phase on the basis of established regional error compensation, and solving an actual phase; and through calibrated camera parameters and a solved absolute phase, calculating three-dimensional coordinate information of a to-be-measured object through a spatial intersection method. The method overcomes phase errors and measurement errors caused by Gamma non-linearity.

Residual phase error compensation circuit 104 performs differential detection between pilot symbols included in an OFDM signal to compensate for residual phase errors of the OFDM signal and then propagation distortion compensation circuit 105 compensates for propagation distortion of the OFDM signal using the re-coded signal as a known signal.

The invention discloses an improved high-resolution SAR (synthetic aperture radar) imaging self-focusing method. The method mainly comprises the following steps that: range pulse compression, preliminary movement compensation and range direction FFT are sequentially performed on radar echo signals, so that movement compensated radar echo signals and the simplified form of the movement compensated radar echo signals can be obtained sequentially; the simplified form of the movement compensated radar echo signals is multiplied by an azimuth Dechirp function; two-dimension interpolation is performed along the range and azimuth directions respectively; after two-dimension interpolated radar echo signals are obtained, IFFT is performed along the range direction, so that phase history-domain data can be obtained; envelope error compensation of the phase history-domain data can be accomplished through adopting an image shift SAR self-focusing algorithm, the phase error of the phase history-domain data of which the envelope error compensation has been completed can be solved through utilizing a conjugate gradient algorithm; after the phase history-domain data of which the envelope error compensation and phase error compensation have been completed are obtained, IFFT is performed along the azimuth direction, so that a high-resolution SAR image with an excellent focusing effect can be obtained.

The present invention relates to a method for correcting the phase error of the position signal of the no-position transducer brushless DC motor, which belongs to the method for correcting the phase error of the position signal of brushless DC motor. The correcting method controls a first afterflow current average value of the afterflow part in the 60 degree non-conductive interval after the negative 120 degree conductive interval of the electric motor phase winding same to a second afterflow current average value of the afterflow part in the 60 degree non-conductive working interval after the positive interval of the electric motor phase winding, to realize the phase error compensation of the position signal of the no-position transducer brushless DC motor. The specific method is measuring respectively the current average values of the two currents of the first current and the second current, inputting the deviation value of the average value of the two afterflow currents of the first and the second afterflow current as the feedback quantity to the PI regulator, and regulating the average value of the first current afterflow current equal to the average value of the second current afterflow current through the PI regulator. The correcting method can automatically correct the phase error of the position signal of the no-position transducer brushless DC motor, the realization is easy and the real-time property to the phase error of the position error is good.

A radar acquires a formed SAR image of radar scatterers in an area around a central reference point (CRP). Target(s) are within the area illuminated by the radar. The area covers terrain having a plurality of elevations. The radar is on a moving platform, where the moving platform is moving along an actual path. The actual path is displaced from an ideal SAR image acquisition path. The radar has a computer that divides the digital returns descriptive of the formed SAR image into multiple blocks, such as a first strip and an adjacent strip. The first strip is conveniently chosen, likely to generally align with a part of the area, at a first elevation. An adjacent strip covers a second part of the area at a second elevation. The first strip is overlapping the adjacent strip over an overlap portion. The first and second elevation are extracted from a terrain elevation database (DTED). Horizontal displacement of returns (range deviation) is computed for each strip using the elevation information from the terrain elevation database. Taylor series coefficients are computed for the horizontal displacement due to terrain elevation using the ideal path, the actual path and central reference point. Actual flight path deviation is available at each pulse position while azimuth frequency is given in azimuth angle off mid angle point. Remapping between indices in two arrays is also computed. Phase error compensation and compensation in azimuth (spacial frequency) is computed using the Taylor series coefficients, a Fast Fourier Transform and an inverse Fast Fourier Transform for each strip. Phase error compensation is applied to the digital returns from each strip to obtain the SAR image. The SAR image is further improved by having the first strip corrected data and the second strip corrected data merged over the overlap portion to generate a relatively seamless SAR image.

A fractional-type phase-locked loop circuit, for synthesizing an output signal multiplying a frequency of a reference signal by a selected fractional conversion factor, includes a frequency divider for generating a feedback signal dividing the frequency of the output signal by a frequency division factor selectable among at least two different integer-value division factors, and frequency divider control means for causing the frequency division factor to vary between the at least two integer-value division factors in a pre-defined number of cycles, thereby an average frequency division factor over said pre-defined number of cycles has a fractional value. Means are provided for compensating a phase error introduced by the frequency divider on the basis of a value indicative of the phase error obtained from said frequency divider control means. The phase-error compensation means includes rounding means, receiving an input binary code with a first number of binary digits, indicative of the phase error value, and providing an output binary code, with a second number of binary digits lower than the first number of digits, defining a rounded phase error value.

The invention discloses an error compensation device for a sin/cos encoder, belongs to a digital signal error compensation device, solves the problem that the conventional error compensation system requires a special error tester and is used for compensating and correcting various errors of output signals of the sin/cos encoder. The error compensation device comprises a differential amplifier, an analog-digital (AD) conversion circuit, and a direct current error compensation module, an amplitude error compensation module and a phase error compensation module which are connected in series in turn. The direct current error compensation module and the amplitude error compensation module eliminate direct current errors and amplitude errors in the output signals of the encoder in turn, and input a processing result to the phase error compensation module; and the phase error compensation module converts phase errors into direct current errors and amplitude errors through phase shift and a frequency multiplier, and compensates the direct current errors and the phase errors to obtain two paths of ideal high-quality sinusoidal/cosine signals. The device is easy and convenient to implement, and good in use effect and provides a basis for reducing interpolation errors and improving interpolation accuracy and resolution.

An adaptive phase-locked loop (PLL) circuit produces an output signal having a frequency in reference to the frequency of a reference signal. The PLL circuit includes an oscillator configured to generate the output signal according to a frequency control signal, and a processing circuit configured to generate a feedback signal deriving from the output signal. An adjustable shift circuit is provided to time-shift the feedback signal. The PLL further includes a phase comparison circuit configured to generate a phase error signal indicating a phase error between the time-shifted feedback signal and the reference signal, and a control circuit configured to generate the frequency control signal based on the phase error signal. The adjustable shift circuit adjusts a time-shift amount to time-shift the feedback signal according to the phase error signal.

A circuit and method for generating a delayed event following a trigger pulse occurring at a random time between clock pulses is disclosed. The circuit includes a clock circuit, a voltage converter, an analog-to-digital converter circuit, a memory storage circuit, and a summing circuit. The method includes representing the time between the triggering pulse and a subsequent clock pulse as a voltage, converting the voltage to a stored digital value, and defining a desired delay time by adding a first time determined by counting a predetermined number of clock cycles to a second time determined by converting the stored digital value first to an analog value and then to a time value.

The invention relates to processes and devices which make it possible to directly modulate an RF carrier with a quadrature signal. It consists in filtering (504) this quadrature signal around zero so as to introduce alternately (507, 508) on each of the channels a low-frequency subcarrier that will serve as reference. Each of these channels is alternately demodulated in a synchronous manner (519) cosine-wise and sine-wise. The demodulation signal is filtered (523) so as to recover the subcarrier marred by modulation errors. The measurement of these errors (524) allows feedback correction (503) of the quadrature signal. It makes it possible to perform the major part of the operations in the digital processor (501) and enables direct vector modulation to be made possible at millimetre frequencies.

The invention discloses a phase error compensation method for large view field adaptive regional Gamma precorrection. A standard N-step phase shift sinusoidal grating image is projected through a projector on the surface of a measured object; a camera is adopted to acquire the projected image; through carrying out phase demodulation on the phase shift image, the phase value of each pixel point is calculated and acquired, and thus, the three-dimensional surface information of the measured object is obtained reversely. In a large view field condition, Gamma values have large differences in a measurement range, residual errors exist when a single Gamma value is adopted for precorrection compensation, a least square fitting method is adopted to acquire the actual Gamma value at each pixel point position, the allowable maximal Gamma value change range deltaG is set to be a threshold according to the Gamma value distribution condition, the measurement region is divided, and thus, multiple Gamma values are adopted to carry out pre-coding correction on the ideal phase shift sinusoidal grating image, and phase errors caused by Gamma nonlinear distortion can be compensated.

The present invention provides a novel optical synthesis aperture imaging system based on the optical fiber array. The high-resolution image can be obtained by the imaging technique of synthesizing a plurality of small apertures to a synthesis aperture. The acquired accomplishment of optical synthesis aperture imaging in the high resolution imaging displays that the technique has a wide developing prospect. The invention receives the optical wave radiated from the target by a Cassegrain telescope array. The optical fiber is coupled in a single-mode polarization-preserving fiber for transmitting. An optical fiber collimator array is used for leading to coherent imaging of the light beam. The phase error compensation is executed through a piezoelectric ceramic phase modulator and an optical fiber delay line. The whole set of equipment goes for miniaturization and lightening, and can be applied in the fields of astronomical measurement, remote sensing the plant cover, monitoring the environment and disaster and the like.

The invention discloses a compressive sensing SAR sparse self-focusing imaging method with optimum image entropy. The method is targeted for the influence of azimuth phase errors in a SAR echo signal measurement model on compressive sensing SAR imaging, and the problem of estimation and compensation of unknown phase errors in a compressive sensing SAR imaging model; azimuth phase error characteristics and sparse target characteristics in the imaging model are utilized, and compressive sensing SAR image entropy is adopted as an evaluation criteria; relationship of SAR azimuth echoes and observed objects are utilized to estimate the azimuth phase errors in each iteration processing process; then, phase error compensation is carried out on the compressive sensing imaging model; and next, compressive sensing SAR imaging is carried out, and a successive iteration method is utilized to enable the image entropy of the compressive sensing SAR imaging to be optimum, thereby improving compressive sensing SAR imaging quality.

The invention discloses a fast factorized back-projection SAR self-focusing method. A phase error optimization model is established by combining a fast factorized back-projection imaging algorithm (FFBP), and the optimization model is solved by using a coordinate descent method and a secant method so that the problem of phase error compensation can be effectively solved. Compared with the methods in the prior art, the phase error can be more accurately estimated and a great focusing SAR image can be obtained so that the problems of high computational burden, low accuracy and low adaptability of the existing FFBP self-focusing method can be solved, and accurate motion error estimation and great focusing combining FFBP imaging can be realized.

An apparatus and method for compensating for a phase error in a wireless communication system are provided. The apparatus includes a reception modem, a transmission modem, a Common Phase Error (CPE) compensator, a first channel estimator, a phase compensator, and a second channel estimator. The reception modem demodulates and decodes a signal received. The transmission modem encodes and modulates a signal for transmission. The CPE compensator compensates for phase errors of at least two symbols constituting a signal. The first channel estimator estimates channels for respective bursts. The phase compensator compares phases for the channels for the respective bursts with each other and compensates for a phase difference between at least two bursts. The second channel estimator estimates an interference channel.

The invention relates to a multi-dimensional synthetic aperture radar motion error extraction and compensation method, which belongs to the technical field of radar. The method includes: extracting motion parameters of a synthetic aperture radar (SAR) from a motion sensor, and projecting the motion parameters to its dimension; analyzing the error accuracy of the motion parameters to determine whether the accuracy requirements are met? If yes, perform motion compensation directly, if not, combine the radar parameters estimated from the SAR raw data with the radar motion parameters extracted from the motion sensor, and then analyze the error accuracy. If the error accuracy meets the requirements, the focus quality analysis is performed, and if the focus quality is met, the compensation is completed. If not, the phase error of the radar echo signal is estimated from the SAR raw data, and the phase error compensation is performed, and then the image is focused quality analysis. The invention can distribute the compensation accuracy to reduce the influence of the sensor accuracy on the motion compensation.

The invention belongs to the technical filed of radar and discloses an unmanned aerial vehicle synthetic aperture radar imaging range-dependant map drift method, improving the estimation precision of doppler rate. The range-dependant map drift method includes receiving the echo signal in the set time period, and performing coarse compensation, distance unit migration correction and distance matching filtering in order to obtain coarse image data; segmenting the coarse image data in the azimuth direction to obtain N sub-aperture data blocks; azimuthally de-skewing the sub-aperture data blocks, dividing the sub-aperture data blocks into L distance units, and estimating the second order phase error of each sub-aperture data block; solving the phase error function corresponding to each distance unit in each sub-aperture data block and compensating the residual phase error compensation for the corresponding distance unit; and azimuthally compressing the data after residual phase error compensation to obtain the focused SAR image.

The invention discloses a self-focusing method for compensating geosynchronous synthetic aperture radar (GEO SAR) ionized layer scintillation amplitude-phase errors. The self-focusing method includes firstly partitioning initial echo data acquired by a GEO SAR to obtain a plurality of sub-scenes, subjecting each sub-scene to compensation processing, and performing splicing to obtain a self-focusing result, wherein the compensation processing includes performing dechirp processing to the initial echo data to obtain S<de>(n, m), initializing an amplitude compensation value alpha<n> and a phase compensation value psi<n> to be 0, respectively establishing an amplitude error model and a phase error compensation model as to the S<de>(n, m), respectively calculating an image entropy E and an image entropy E

, using the E and the E

as cost functions to perform iteration updating on the alpha<n> and the psi<n> until a minimum value of the cost functions are reached, and using an ultimately updated amplitude compensation value and phase compensation value to compensate the S<de>(n, m) and perform fast Fourier transform (FFT) imaging to obtain a compensation processing result of a current sub-scene. The self-focusing method is capable of accurately estimating and compensating amplitude fluctuation and phase errors of echo data introduced by ionized layer scintillation.

The invention provides a linear array SAR fast auto-focusing imaging method based on maximum sharpness. The method is based on the maximum sharpness criterion and backward projection imaging principleof a linear array SAR 3D image. First, a phase error estimation equation of backward projection auto-focusing imaging is constructed by using an image sharpness partial derivative. Then, the phase error estimation equation is quickly and approximately solved through a conjugate gradient method, and quick estimation of phase error in linear array SAR echo is realized. Finally, phase error compensation and backward projection imaging are carried out, and linear array SAR backward projection auto-focusing imaging is realized. The low-frequency, high-frequency and randomly distributed phase errors in linear array SAR echo data can be quickly estimated without knowing the prior information of phase error distribution. The linear array SAR fast auto-focusing imaging method based on maximum sharpness is suitable for linear array SAR fast auto-focusing imaging under complex motion trajectories.

Electronically controllable arrayed waveguide gratings (AWGs) with integrated phase error compensation for each individual arm of the array of waveguides. These AWGs and associated methods for static and dynamic phase compensation enable the fabrication of tunable AWGs which can track one or more drifting channels of an AWG.