86 results about "Nyquist frequency" patented technology

An oscilloscope having a Nyquist frequency lower than an analog bandwidth includes an input configured to receive a signal under test; an analog-to-digital converter (ADC) to receive the signal under test, sample the signal under test at a sample rate, and produce digital samples of the signal under test; one or more processors configured to execute code that causes the one or more processors to: determine a set of candidate unit intervals by generating corresponding candidate histograms using the candidate unit intervals; determine a best unit interval from the candidate unit intervals based upon entropy measures of each candidate histogram; and reconstruct a representation of the signal under test using the digital samples and the best unit interval.

The invention relates to the technical field of signal processing, in particular to a large-bandwidth signal source bandwidth flatness compensation method and device based on an FPGA (Field Programmable Gate Array), and the method comprises the steps: playing signal data with required bandwidth through an analog front end based on the FPGA, and measuring an original amplitude-frequency response curve of the signal data through a frequency spectrograph; calculating the amplitude-frequency response of the compensation filter, obtaining a compensation filter coefficient, and quantifying the compensation filter coefficient; sending the quantized compensation filter coefficient to an FPGA to compensate the signal data, playing the signal data through an analog front end, and measuring a first pre-compensation amplitude-frequency response curve in a Nyquist frequency range through a frequency spectrograph; and determining a frequency range exceeding the set bandwidth flatness according to the first pre-compensation amplitude-frequency response curve, and performing independent compensation. Therefore, the influence caused by nonlinearity of a DAC device and related circuits is overcome, the amplitude-frequency response of a large-bandwidth signal source is effectively compensated, the signal flatness in the bandwidth is improved, and the stability and reliability of the system are enhanced.

Disclosed is a coherent optical transceiver for optical communication including a transmitter, a receiver, and a PIC. The transmitter includes a DAC and a driver. A modulator in the PIC limits a signal spectrum of an output optical signal within a Nyquist frequency band. The receiver receives an input optical signal from the PIC and converts the input optical signal to an input analog electrical signal. An ADC converts the input analog electrical signal into an input digital electrical signal indicative of the input optical signal at an ADC sampling rate. The DSP includes a linear filter to equalize intersymbol interference, a post filter, and an MLSE to determine symbols corresponding the input optical signal. The driver and the post filter are first order filters with transfer function G(z)=1+az−1, where a is between 0 and 1.

The invention provides a 3D GS anti-aliasing rendering method fused with adaptive expansion, which comprises the following steps: under a 3D GS framework, before projecting a 3D Gaussian to a screen space, firstly applying a 3D Gaussian low-pass filter to the 3D Gaussian to suppress high-frequency components exceeding a Nyquist frequency and reduce the probability of occurrence of aliasing artifacts; after a three-dimensional Gaussian is projected to a screen space, a resolution self-adaptive expansion coefficient adjusting mechanism is used, and the physical size of a Gaussian point can be automatically adjusted according to the image resolution. And finally, in combination with a super-sampling technology, it is ensured that the colors of the Gaussian primitives can reasonably influence the pixels. According to the multi-guarantee 3DGS anti-aliasing rendering method, the aliasing problem caused by overlarge coverage of Gaussian points is prevented under the low resolution, and detail loss and edge erosion are avoided under the high resolution.

The invention discloses a single-channel double-gain high-precision measurement method, system and device and a medium, and the method comprises the steps: setting an oversampling rate, and achieving a signal-to-noise ratio of a preset high value when an analog input signal is oversampled based on the oversampling rate; correlation mapping exists among the oversampling rate, the signal sampling frequency and the Nyquist frequency; combining the two analog-to-digital converter channels to sample the same analog input signal; the channels of the two analog-to-digital converters are provided with programming gain amplifiers which are configured to receive input signals with different numerical values and expand the signal capture range of the analog-to-digital converters by using different gain levels; when signal sampling is executed, signal sampling operation is carried out based on the oversampling rate and the signal input ranges of different numerical values; according to the invention, the nominal condition and the fault condition of the signal can be measured at the same time, a wider signal measurement range is provided, and the signal analysis precision is improved.

The invention discloses a digital channelization rapid signal processing method and system based on Nyquist folding, and the method comprises the steps: firstly carrying out the undersampling of a signal received by an antenna through an NYFR structure through an analog period non-uniform sampling pulse string generated by a local oscillator, and folding a frequency band of a signal spectrum to be below a Nyquist frequency; secondly, discrete digitization is carried out on the modulation signal which is folded below the Nyquist frequency by using an ADC (Analog to Digital Converter) integrated by the RFSoC; and finally, performing digital channelization processing on the discrete and digitized data based on an IDFT (Inverse Discrete Fourier Transform) multiphase filtering structure to divide the data into a plurality of sub-channels, demodulating the plurality of sub-channels which arrive at the same time in parallel by a receiver, and reconstructing a signal received by an antenna, thereby completing rapid signal receiving and processing of the NYFR structure. According to the invention, the instant ultra-wide frequency band real-time monitoring and processing capability is obviously improved, the instant ultra-wide frequency band signals can be received and processed, and the cost and the complexity are reduced.

The invention discloses a high-frequency disturbance suppression method based on repeated sampling in a tilting mirror system, which is mainly used for tracking and controlling real-time high-frequency disturbance signals and reducing optical axis errors, especially for high-frequency disturbance signals which are limited in sensor sampling and difficult to suppress. The method comprises the steps of identifying whether an unknown signal is aliasing or not through a sampling scheme with a variable sampling period and obtaining frequency information of actual disturbance, and then recovering an actual high-frequency signal component exceeding the Nyquist frequency of a sensor through a repeated sampling algorithm. And finally, designing a multi-rate parallel repetitive control scheme to compensate and suppress high-frequency disturbance signals exceeding the closed-loop bandwidth. The method can effectively solve the problem that tracking control is difficult to realize due to aliasing of high-frequency disturbance signals when sampling of the image sensor is limited, and improves the anti-interference capability of the system.

A method for filtering periodic noise and a filter using the method are provided. The method includes: obtaining an input signal; detecting a fundamental frequency corresponding to a maximum peak in a spectrum of the input signal, detecting a harmonic frequency according to the fundamental frequency, and detecting an aliasing frequency corresponding to the harmonic frequency in response to the harmonic frequency corresponding to the fundamental frequency being greater than a Nyquist frequency of the input signal; filtering the fundamental frequency and at least one of the harmonic frequency and the aliasing frequency of the spectrum to generate a first filtered spectrum, and restoring the input signal according to the first filtered spectrum to generate an output signal; and outputting the output signal. The method for filtering the periodic noise and the filter using the method may filter the periodic noise in the input signal affected by an aliasing effect.

The invention provides a capacitor voltage feedforward passive enhancement control method based on a passivity criterion, and belongs to the technical field of grid-connected inverter control, and the method comprises the steps: S1, system modeling and stability analysis; s2, controller parameter design; s3, carrying out passivity criterion analysis; and S4, designing a control scheme. According to the invention, a novel CVF-AD adaptive control scheme considering delay compensation is designed based on a passivity stability criterion. The inverter system adopting CVF-AD adaptive control can stably operate under the condition of not considering the impedance of a power grid, so that the grid-connected inverter system shows a passive characteristic under the Nyquist frequency, thereby realizing a strong plug-and-play function of the inverter, reducing grid-connected current distortion caused by background harmonic waves of the power grid, and improving the reliability of the grid-connected inverter system. And moreover, the use of sensors is reduced, and good economical efficiency is achieved.

The invention relates to a low-frequency noise data processing method and device, electronic equipment and a vehicle, and relates to the technical field of data processing, and the method comprises the steps: firstly obtaining a target frequency corresponding to a to-be-determined frequency spectrum component; determining a Nyquist frequency corresponding to the target frequency; according to the Nyquist frequency, obtaining the time domain sampling number R required by the target frequency; selecting a target sequence corresponding to the first R sampling points in the displacement sequence, and performing butterfly recursion calculation of fast Fourier transform on the target sequence to obtain a result used for determining sound pressure level information corresponding to the frequency spectrum component, the displacement sequence is obtained by performing butterfly odd-even displacement of fast Fourier transform according to a time domain sequence corresponding to the low-frequency noise data. According to the technical scheme, for analysis and calculation of low-frequency noise, it can be guaranteed that the precision error is within the acceptable range, meanwhile, calculation redundancy is reduced, and calculation power is saved.

The present application relates to the technical field of data processing, and particularly relates to a method and apparatus for processing noise data, and an electronic device and a vehicle. The method comprises: firstly acquiring a target frequency corresponding to a spectrum component to be determined; determining a Nyquist frequency corresponding to the target frequency, wherein the target frequency is lower than a preset frequency threshold value; then, according to the Nyquist frequency, determining a time-domain sampling number R required by the target frequency; and selecting, from among a displacement sequence, a target sequence corresponding to the first R sampling points, and performing butterfly recursive computation of a fast Fourier transform on the target sequence, wherein an obtained result is used for determining sound pressure level information corresponding to the spectrum component, and the displacement sequence is obtained by means of performing butterfly odd-even displacement of a fast Fourier transform according to a time-domain sequence corresponding to the spectrum component. By means of applying the technical solution of the present application, for the analysis and computation of low-frequency noise, the computation redundancy can be reduced, and the computing power is saved on while ensuring that a precision error is within an acceptable range.

Circuitry for determining an impedance of an electrochemical cell comprising at least one first electrode and a second electrode, the circuitry comprising: drive circuitry configured to apply a stimulus to the electrochemical cell, the stimulus having a stimulation frequency and a stimulation amplitude; and measurement circuitry configured to: sample an output of the electrochemical cell at a sampling frequency to generate an output signal; determine an output amplitude of output signal at one or more alias frequencies, the one or more alias frequency based on the stimulation frequency and the sampling frequency; and determine the impedance of the cell at the stimulation frequency based on the output amplitude at the one or more alias frequencies and the stimulation amplitude; and control circuitry configured to: control the sampling frequency and the stimulation frequency such that a Nyquist rate of the sampling frequency is greater than stimulation frequency.

The present disclosure provides a calibration method, system, device, medium and program product for sampling time error, and the calibration method includes: obtaining the calibration times of different channels of an analog-to-digital converter to a preset direction; obtaining the difference between data correlations based on the calibration times; adjusting the preset direction based on the difference to obtain a target direction; and calibrating the sampling time of the channel based on the target direction. The present disclosure achieves calibration of the sampling time by obtaining the calibration times of different channels of an analog-to-digital converter to a preset direction, and then obtaining the difference between data correlations to adjust the preset direction. The sampling time error calibration can be completed when any Nyquist frequency domain signal is input, and the calibration direction judgment and error correction can be completed without the need for TIADC to design additional calibration channels, thereby reducing hardware circuit overhead, expanding the application scenarios of the error calibration method, and having universal applicability.

The application provides a sidelobe suppression method without loss of resolution, which can completely remove sidelobes and does not lose signal resolution. The method is based on the characteristic that the main lobe width of IPR is twice the sidelobe width. If N sample data of IPR are set, the main lobe width is 4xpi / N, and the sidelobe width is 2xpi / N. By using the fact that the main lobe width is different from the sidelobe width, the positions of the main lobe and the sidelobe in IPR can be located. As long as the positions of the main lobe and the sidelobe are determined, the unwanted sidelobe can be eliminated. The method provided by the application does not need to limit the data sampling rate to be an integer multiple of Nyquist frequency, and is directly applied to the spectrum of a signal, and is simple to calculate.

Provided is a machine learning image processing method, wherein: a first frequency characteristic of a first teacher image is calculated; a sample frequency characteristic of a sample image, which serves as a sample of a low-quality image obtained by imaging with a low-image-quality endoscope, is calculated; a ratio of the sample frequency characteristic and the first frequency characteristic is calculated as a first frequency response characteristic; the first frequency response characteristic is compared with a predetermined second frequency response characteristic for student image generation; when a Nyquist frequency of the first frequency response characteristic is N2 and a Nyquist frequency of the second frequency response characteristic is N1, if N1 < N2, the image size of the first teacher image is reduced to generate a second teacher image; and if N1 ≥ N2, the first teacher image is reduced in image quality using a low-pass filter set on the basis of the second frequency response characteristic to generate a first student image.

The invention belongs to the field of magnetic resonance sounding signal noise filtering, and particularly relates to a magnetic resonance sounding signal de-noising method based on backtracking generalized OMP, and the method comprises the steps: employing a magnetic resonance sounding water detector to carry out the sampling of a sparse signal at a frequency lower than the Nyquist frequency, and obtaining a noisy MRS signal; converting the noisy MRS signal into a two-dimensional matrix signal; dictionary learning is carried out on the two-dimensional matrix signals through a KSVD algorithm, and an updated dictionary is obtained after iteration; calculating a recovery matrix and measurement data by using an independently distributed Gaussian random matrix; performing iterative operation on the measurement data by using a backtracking generalized orthogonal matching pursuit algorithm, selecting an atomic sequence of maximum projection of the measurement data and a recovery matrix module, and obtaining a sparse coefficient matrix of the measurement data under the recovery matrix; and calculating a recovery signal according to the dictionary and the sparse coefficient matrix of the measurement data under the recovery matrix.

An oscilloscope having a Nyquist frequency lower than an analog bandwidth includes an input configured to receive a signal under test; an analog-to-digital converter (ADC) to receive the signal under test, sample the signal under test at a sampling rate, and generate digital samples of the signal under test; one or more processors configured to execute code that causes the one or more processors to: determine a set of candidate unit intervals by generating corresponding candidate histograms using the candidate unit intervals; determine a best unit interval from the candidate unit intervals based on entropy measures of each candidate histogram; and reconstruct a representation of the signal under test using the digital samples and the best unit interval.

The invention relates to the technical field of grid-connected inverters, in particular to a method for correcting positive virtual impedance of an LCL type inverter in a Nyquist frequency, which comprises the following steps of: accurately determining parameters of capacitor voltage feedback branches in an LCL filter, establishing an equivalent formula of virtual impedance, and adjusting parameters in primary differential feedback so as to correct the positive virtual impedance of the LCL type inverter in the Nyquist frequency. The method successfully widens the positive damping frequency range, optimizes the impedance characteristics of the inverter through the virtual impedance of the parallel proportional term, the primary differential term and the secondary differential term and the calculation of the total parallel impedance formula, and obtains the impedance characteristics of the inverter by drawing various impedance-frequency curves. Comprising a virtual impedance-frequency curve, a parallel impedance-frequency curve and a primary differential impedance-frequency curve, and an intuitive impedance characteristic analysis tool is provided for a system designer and an engineer; and finally, by drawing a total impedance-frequency curve and verifying whether the system maintains the positive resistance characteristic in the Nyquist frequency range, the stability of the system is ensured.

The application provides a passive equalizer for inter-core particle interconnection and an inter-core particle interconnection system, which comprises upper sawtooth metal copper wires, lower sawtooth metal copper wires, a first via and a second via; the upper sawtooth metal copper wires are provided with the second via on one side and connected to the lower sawtooth metal copper wires through the first via on the other side; and the upper sawtooth metal copper wires and the lower sawtooth metal copper wires are both provided in a sawtooth shape and staggered. The double-layer sawtooth cross metal copper wires embedded in the metal grounding layer can effectively solve the serious inter-symbol interference (ISI) problem existing in the high-speed parallel data transmission system, and the voltage transmission curve of the channel in the transmission system is flattened in the range of direct current frequency and Nyquist frequency, so that the eye diagram quality of the receiver is obviously improved.

A test and measurement instrument includes one or more ports for receiving a signal from a device under test (DUT), an array of analog-to-digital converters (ADCs) for receiving the signal, a data collector for outputting a sample from each ADC during an ADC clock cycle, and one or more processors for providing a sampling clock to each ADC with a different clock phase than other ADCs to effect non-uniform sampling at or below a Nyquist frequency and to cause the ADCs to output non-uniformly spaced samples.A method includes receiving a signal from a device under test, providing a sampling clock to each ADC in an array of ADCs that has a different clock phase than the clock phases provided to other ADCs, causing a non-uniform sampling pitch at or below a Nyquist frequency, sampling the signal at a non-uniform sampling clock, and outputting the non-uniformly spaced samples.

The invention is suitable for the technical field of electronic microphone audio signal processing, and provides an electronic microphone audio signal processing system and method, and the system comprises a server which is connected with a signal collection module, a digital signal processing module, a digital-to-analog conversion module, and an output module. The signal acquisition module comprises a sound sensor, an analog front end and an analog-to-digital converter; the sound sensor adopts an MEMS microphone array and converts sound wave pressure change into an analog electric signal; a pre-amplifier, a biasing circuit and an anti-aliasing filter are arranged in the analog front end; the pre-amplifier amplifies an electric signal output by the microphone; the anti-aliasing filter is used for filtering high-frequency components higher than the Nyquist frequency before analog-digital conversion, and aliasing distortion is prevented. According to the invention, digital audio signals can be accurately processed in real time, echoes are effectively eliminated, noise is suppressed, the volume is stabilized, the voice definition and the tone quality are improved, and the audio signal processing quality of the electronic microphone is greatly improved.

The invention relates to the technical field of image degradation processing, in particular to a method for evaluating the degradation degree of optical system imaging caused by atmospheric factors. According to the method, a systematic evaluation system for the influence of atmospheric factors on optical imaging is constructed, the modeling processes of the fog aerosol MTF and the long exposure turbulence MTF are integrated, the Nyquist frequency is used as a bridge, the atmospheric coherence length when the fog aerosol MTF and the long exposure turbulence MTF are equivalent is solved, and a breakthrough from independent factor analysis to synergistic effect quantification is achieved. An evaluation model is constructed by fusing multiple parameters such as optical thickness, atmospheric coherence length, wavelength, spatial angular frequency and the like, and a complete technical chain of modeling-simulation-evaluation is formed by combining Fourier transform image simulation with evaluation indexes such as peak signal-to-noise ratio, structural similarity index and the like. And a solution with theoretical preciseness and engineering practicability is provided for predicting the degradation degree of the optical imaging system in a complex atmospheric environment.

A system and method for synchronizing to a received signal in an IR-UWB receiver including sampling the received signal in a frequency that is less than a Nyquist frequency of the received signal; for each part of the sampled received signal that is equal in length to a synchronization symbol: calculating a cross-correlation between the synchronization symbol and the part of the sampled received signal that is equal in length to the synchronization symbol; calculating at least one autocorrelation, where each autocorrelation is performed between the results of the cross-correlation and the results of the cross-correlation delayed by a time lag that equals one or more time-durations of the synchronization symbol; accumulating the results of each of the at least one autocorrelation to obtain at least one coarse synchronization window; and analyzing the at least one coarse synchronization window to detect presence of the synchronization symbol in the received signal.

The signal detection circuit (10) includes frequency shift units (2, 3, 4, 5) that shift the frequency of an input signal from an analog-digital converter (1), which converts an analog signal into a digital signal, and output the input signal so that the center frequency of the band of the input signal becomes the Nyquist frequency, moving sum calculation units (6, 7, 8) that calculates the sum over a fixed period of time of the absolute values ​​of the signal output from the frequency shift units, and a signal detection unit (9) that detects a specific signal included in the input signal using the calculation result by the moving sum calculation unit.

The present disclosure provides an OCT imaging system to reduce or eliminate frequency-domain aliasing artifacts. The frequency is shifted using a carrier frequency to define a sampling range substantially centered on the carrier frequency. An image of the sample is generated from a displayed imaging range that consists of a subset of the frequencies within the sampling range. Furthermore, the system may be configured to determine the carrier frequency such that a Nyquist frequency corresponding to the shifted frequency is extended beyond either an upper or a lower bound of an OCT quality envelope corresponding to the first portion of light. Additionally, the carrier frequency may be determined such that a lower bound of the OCT quality envelope is greater or less than a zero-frequency DC limit.

The invention relates to a high-speed and high-precision current steering type digital-to-analog converter with excellent dynamic characteristics, which is characterized in that a segment decoding module receives digital signals and performs segment decoding processing to obtain control signals of each segment and sends the control signals to a switch driving circuit; the switch driving circuit is used for processing obtained control signals of each section, respectively corresponding to an in-phase driving control signal section and a reverse-phase driving control signal section of which the cross points are lower than common-mode voltage, and transmitting the control signals to a control input end of the differential switch array; the differential switch array works to realize the output of a forward analog signal and a reverse analog signal corresponding to a digital signal, so that the influence of a small load change effect, especially the influence of the problems of limited output impedance caused by parasitic capacitance, signal-dependent switching transient and the like on the dynamic characteristics of the current steering digital-to-analog converter can be solved; the design scheme has good dynamic characteristics when the signal frequency is close to the Nyquist frequency band, and the application requirements of multiple fields such as a communication system are met.

The application discloses a new energy automobile power battery thermal balance integrated monitoring system. In the application, a data buffer module effectively isolates a signal source from subsequent circuits through the characteristics of high input impedance and low output impedance, ensures the stability and integrity of the signal in the transmission process, and a self-adaptive gain controller module further optimizes the quality of the signal by monitoring and automatically adjusting the amplifier gain in real time, so that the output signal is ensured to be in a suitable dynamic range, distortion caused by too small signal is prevented, and saturation caused by too large signal is avoided. A data noise suppression module uses a low-pass active filter and a noise gate technology to specifically reduce noise components in the signal, and further improves the quality and definition of the signal. An anti-aliasing filter module effectively removes signal components higher than the Nyquist frequency before signal sampling, prevents aliasing from occurring, and ensures the accuracy of the sampling data.

The invention relates to a rotary machine modulation feature extraction method based on an adaptive Hoyer-L moment envelope spectrum, and the method comprises the steps: firstly collecting vibration or radiation noise data of a rotary machine as a monitoring signal, calculating a spectrum coherence function of the monitoring signal, and obtaining a double-variable spectrogram; dividing a Nyquist frequency band along a frequency axis by adopting frequency resolution; performing spectral integration on each sub-band to generate an enhanced envelope spectrum, and quantifying the modulation intensity of each sub-band based on a comprehensive evaluation index of an L moment and a Hoyer operator; then adaptively optimizing the sub-band with high modulation intensity based on a golden section method; and selecting a sub-band with high modulation intensity to perform spectrum integration along a frequency axis to obtain a demodulation spectrum of the signal. According to the invention, the demodulation performance of the rotating machine in a complex environment can be significantly improved.

The invention relates to the technical field of machine vision, and discloses an enameled wire surface defect detection and classification method based on machine vision, which comprises the following steps: firstly, collecting a wire scanning image, extracting a single-pixel time sequence of a fixed transverse position, performing frequency domain transformation after window processing, and obtaining a single-pixel time sequence; determining the position of a main peak according to the power spectrum in a range from zero frequency to Nyquist frequency; calculating a spiral bispectrum locking degree by taking a main peak as a reference; determining a phase sampling resolution according to the locking degree, and performing phase resampling on a single pixel time sequence and an adjacent pixel time sequence to generate phase-aligned two-dimensional blocks; then parameterizing channel gain and channel bias of each layer of the convolutional neural network by using a spiral bispectrum locking degree, and inputting a two-dimensional block into the network to obtain a defect probability; a binary cross entropy loss function is optimized by taking a power function of the spiral bispectrum locking degree as a sample weight; the arithmetic mean value of the defect probabilities of the same axial section is obtained, and when the mean value reaches or exceeds a preset threshold value, it is judged that defects exist.

This invention discloses a high-speed cable optimization method and system based on impedance continuity compensation, relating to the field of high-speed cable optimization. The method includes: identifying the location, amplitude, and type of each impedance abrupt change point; calculating the reflection phase difference between any two abrupt change points; identifying the locations of coherent traps where reflected signals from multiple abrupt change points coherently superimpose within the Nyquist frequency range; constructing a coherence elimination objective function; determining compensation parameters for geometric pre-compensation, dielectric constant gradient compensation, and active dynamic compensation; adjusting the reflection coefficient amplitude of the abrupt change points according to the target residual impedance abrupt change amplitude; changing the reflection phase distribution according to the optimal control parameters of dielectric constant gradient compensation; and introducing an adjustable reflection coefficient to adjust the standing wave condition according to the target terminal matching impedance value. The advantages of this invention are: effectively eliminating the coherent superposition effect of multi-level reflections in high-speed cables, achieving impedance continuity and signal integrity of high-speed cables across the entire frequency band.