48 results about "Zero frequency" patented technology

The invention provides a 5G self-organizing network coarse synchronization segmentation design method based on a domestic chip, and relates to the technical field of mobile communication, and the method comprises the following steps: S1, according to a sampling rate issued by OAM, capturing an air interface signal according to an NRSSB common period; s2, according to the central frequency point of the receiving end bandwidth, calculating a frequency point difference and carrying out zero frequency shift; s3, segmenting the signal after zero-frequency shift, combining the segmented signal into a window, and carrying out down-sampling processing on the signal; s4, performing AGC gain processing on the signal; s5, performing intra-window judgment on the signals; s6, after the in-window judgment of all the in-window signals is completed, inter-window judgment is carried out; and S7, setting an overtime threshold, and dynamically adjusting the window length. The method has the beneficial effects that the calculation complexity is reduced, calculation resources are efficiently utilized, the calculation efficiency is improved, and the accuracy and reliability of signal detection are high.

The present invention provides a full-decay induced polarization (FDIP) detection system and method for water inrush in tunnels, comprising: through instructions for controlling constant-current high-power transmitting module and multi-channel parallel data acquisition and receiving module, receiving observation data and performing inversion by replacing minimum gradient support constraint to traditional smooth constraint, introducing data shape as prior information into inversion objective function, and constructing and solving focusing inversion formula of FDIP detection for water inrush in tunnels based on data shape constraint, to update model parameters; completing multi-source information acquisition of apparent resistivity, polarizability and the like and multi-parameter inversion imaging of zero-frequency resistivity, relaxation time, chargeability and frequency correlation coefficient, effectively reduce electromagnetic interference and improve detection efficiency, greatly meet the urgent requirement for detecting sudden water inrush disaster sources in front of tunnel face under construction, and having strong research significance and application value.

The invention discloses a noise suppression method for time-frequency electromagnetic detection data. Corresponding signal processing work is carried out on analog signals through a front-end signal conditioning circuit and digital signals obtained after AD sampling on an FPGA platform so as to improve the signal-to-noise ratio of input signals. And in a time domain electromagnetic detection mode, denoising processing is carried out on the transient sampling signal by using a superposition average algorithm. In a frequency domain electromagnetic detection mode, a harmonic sampling signal is subjected to digital orthogonal locking amplification algorithm processing, frequency mixing is carried out on the harmonic sampling signal, and the frequency spectrum of the harmonic sampling signal is shifted to be near zero frequency; low-pass filtering is realized through a narrowband filtering extraction module, out-of-band noise is suppressed, and the signal-to-noise ratio of the signal is improved; and further improving the signal-to-noise ratio by using an FFT algorithm, and obtaining the amplitude and phase of the target signal through a CORDIC algorithm.

The invention discloses a frequency-modulated continuous wave laser radar signal generation method, a frequency-modulated continuous wave laser radar signal detection method and a frequency-modulated continuous wave laser radar signal detection system. The system comprises a transmitting end and a receiving end, wherein the transmitting end determines a frequency guard interval between a frequency-modulated continuous wave signal and zero frequency according to a modulation bandwidth of a radar signal and a line width of a transmitting laser; generating a frequency modulation continuous wave signal according to the frequency protection interval, modulating the frequency modulation continuous wave signal, generating radar detection signal light which is to be sent and contains residual carrier waves, performing power amplification on the radar detection signal light, and transmitting the radar detection signal light by using an optical lens; the receiving end receives the reflected signal light reflected by the target; filtering, beat frequency and coherent detection are carried out on the reflected signal light and the radar detection signal light to obtain an electric signal, and the electric signal is converted into a digital signal; performing electric domain filtering on the digital signal, and extracting a residual carrier and a beat frequency signal; performing phase noise compensation on the beat frequency signal based on the residual carrier to obtain a signal after phase recovery; and estimating the distance and the relative speed of the target based on the residual carrier and the phase-recovered signal.

The invention relates to an urban complex environment clutter suppression method for a communication and inductance integrated system. The method comprises the following steps: acquiring multi-frame echo data; sequentially performing distance dimension pulse compression and Doppler dimension coherent accumulation on each frame of echo data to obtain a distance-Doppler frequency spectrum of each frame of echo data; and carrying out band coefficient subtraction on the distance-Doppler frequency spectrum of every two adjacent frames of echo data by using the clutter distribution similarity of the two adjacent frames of echo data to obtain the distance-Doppler frequency spectrum after clutter suppression, the coefficient being the ratio of the zero frequency data of every two adjacent frames of echo data. According to the urban complex environment clutter suppression method for the communication and inductance integrated system, the application of a base station to detect a low, slow and small target in the urban complex environment is met, strong clutter suppression is achieved for zero frequency and nearby Doppler channels, the problem of clutter spectrum diffusion can be solved, the slow moving target detection performance is improved, the signal-clutter-noise ratio is increased, and the method is suitable for large-scale popularization and application. The method is suitable for signals with different bandwidths and transmitting powers.

The invention belongs to the technical field of microwave photons, and provides a double-ring photoelectric oscillator and a stabilizing method thereof. The oscillator is provided with a long ring and a short ring and comprises a stabilizing device; the stabilizing device comprises a first piezoelectric ceramic optical fiber stretcher, a motor space light delay line and a second piezoelectric ceramic optical fiber stretcher; generating two optical probe signals; the first optical probe signal is converted into a first electric probe signal through the long ring; a second optical probe signal is converted into a second electric probe signal through the short ring; an electric probe signal is output after being subjected to detection, coupling and power division; the two frequency mixers respectively carry out homodyne frequency mixing on the electric probe signal and the phase-shifted and non-phase-shifted radio frequency signals to generate a zero-frequency error signal; the two phase-locked loops generate compensation control signals according to the error signals; the control signal adjusts an optical fiber delay line; the stability of the two loops is ensured, the problem of combined signal frequency drift caused by neglecting short-loop delay change is solved, the coherence requirement on optical signals is avoided by electric domain combination, and smooth tuning of the output radio frequency signal frequency is realized.

The application provides a modulation method and system of an orthogonal frequency division multiplexing signal, and belongs to the technical field of wireless communication. The method comprises the following steps: mapping a frequency domain data signal and a pilot signal to be transmitted into a frequency domain resource grid matrix; performing a frequency domain shift operation on each row vector of the frequency domain resource grid matrix, shifting a zero frequency component to the center of the vector, and obtaining a shifted matrix; and performing an inverse fast Fourier transform on each row vector of the shifted matrix, and obtaining a time domain orthogonal frequency division multiplexing symbol matrix as a modulation result. The application constructs the entire frequency domain resource into a two-dimensional matrix, and all subsequent signal processing operations are based on the row vectors of the two-dimensional matrix as a basic unit, and are completed through a series of explicit matrix and vector operation steps. Thus, the IFFT call for the entire frame, which is a black box, is decomposed into individual steps for a single symbol, which are visible and controllable, and the problem of opaque process is solved.

The present application relates to a kind of based on comb spectrum implementation wideband signal transmitting device amplitude phase flatness analytical method, comprising the following steps acquisition measured link's time domain complex IQ sampling data;Perform fast Fourier transform;Zero frequency component is moved to spectrum center;Calculate the index of each target frequency in spectrum array;The amplitude and phase at each index are calculated;Calculate preliminary amplitude error and phase error;Get amplitude flatness distortion;Interlaced phase correction is carried out;Phase unwrapping is carried out;Get phase flatness distortion;Filter out abnormal value;Output amplitude flatness distortion and phase flatness distortion result.The wideband signal transmitting device amplitude phase flatness analytical method based on comb spectrum implementation of the present application, system, device, processor and its computer readable storage medium, around the flatness calibration demand of wideband wireless signal transmitting device, obtains the flatness information of transmitting device from comb spectrum, realizes the asynchronous acquisition and efficient analysis without synchronization.

A method for zero-point correction of an S-parameter model includes: calculating the S-parameters at zero frequency based on the constructed S-parameter model; calculating the error matrix between the S-parameter model and the original S-parameters at zero frequency; calculating the residues corresponding to the preset real poles based on preset real poles and the error matrix; and adding a term to the S-parameter model using the preset real poles and their corresponding residues to obtain the zero-point corrected S-parameter model. This method further corrects the S-parameters after vector fitting and passivity correction, ensuring that the values ​​of the S-parameters at zero frequency remain consistent with the original S-parameters while minimizing disruption of the original model's passivity and maintaining accuracy. This corrects the error of the original model's S-parameters at zero frequency, eliminating errors in subsequent simulations caused by the inaccuracy of the S-parameters at zero frequency.

The invention belongs to the technical field of microwave photons, and provides a double-ring photoelectric oscillator with a stabilizing device and a stabilizing method thereof, the double-ring photoelectric oscillator is provided with a long ring, a short ring and a stabilizing device; the stabilizing device comprises a first piezoelectric ceramic optical fiber stretcher and a motor space light delay line; the radio frequency signal source generates a first optical probe signal and a second optical probe signal through modulation; the first optical probe signal is converted into a first electric probe signal after passing through the long ring; a second optical probe signal is converted into a second electric probe signal after passing through the short ring; the first frequency mixer and the second frequency mixer are used for performing homodyne frequency mixing on the electric probe signal and the radio frequency signal to generate a zero frequency error signal; and the two phase-locked loops generate compensation control signals according to the zero-frequency error signals. According to the invention, by outputting the control signal and adjusting the optical fiber delay line, the stability of two loops is ensured, the problem of combined signal frequency drift caused by neglecting short-loop delay change is solved, and the coherence requirement on two paths of optical signals is avoided by electric field combination.

The application provides a lumped parameter topology for realizing generalized Chebyshev band-pass frequency response by using lumped parameter elements, which specifically includes two types of structures, GCL and GCB. The generalized Chebyshev band-pass frequency response includes two types of double-side generalized Chebyshev band-pass frequency response and single-side generalized Chebyshev band-pass frequency response. The response is characterized in that the response amplitude in the passband is equal ripple fluctuation, has three transmission poles, and two transmission zeros can be flexibly placed at limited frequencies, which are any positive frequencies except zero frequency and infinite frequency. The GCL structure is used for realizing double-side generalized Chebyshev band-pass frequency response, and the GCB structure is used for realizing single-side generalized Chebyshev band-pass frequency response. The application effectively overcomes the limitations of the prior art, and realizes more complex frequency response by flexibly setting transmission zeros.

The invention discloses an optical frequency comb locking system for eliminating carrier envelope phase shift frequency. The system comprises an optical frequency comb, a repetition frequency detector, a carrier envelope phase shift detector, an attenuator, an operational amplifier, a filter, a power divider, a double-balanced mixer, a bias voltage and a phase-locked loop. According to the system, the sum value and the difference value frequency of the repetition frequency of the optical frequency comb and the carrier envelope phase shift frequency are extracted and mutually locked, so that the purposes of locking the carrier envelope phase shift frequency to zero frequency and reducing the locking difficulty of the optical frequency comb are achieved. According to the method, the defect that a traditional optical frequency comb is high in locking difficulty is overcome, carrier envelope phase shift frequency control is more simplified, feasibility of productization and high integration is achieved, meanwhile, universality is achieved, and the method can be widely applied to different types of optical frequency comb systems.

The application relates to the radar technical field and discloses a continuous wave radar detection method, which comprises the following steps: generating an initial radio frequency carrier signal; applying a preset frequency offset to the initial radio frequency carrier signal to generate a transmission signal; radiating the transmission signal to a detection space through a transmission antenna; receiving a return signal formed by reflection of the transmission signal by a target in the detection space through a receiving antenna; and mixing the return signal with the initial radio frequency carrier signal to obtain a first intermediate frequency signal; wherein the preset frequency offset is configured so that, for a stationary target, the first intermediate frequency signal is a signal with a frequency equal to a preset non-zero frequency value; and the first intermediate frequency signal is processed to obtain information related to the state of the target. The spectrum of the effective signal is actively shifted to a frequency point away from a high-noise low-frequency area, and the detection sensitivity for stationary or micro-motion targets is enhanced. The application further discloses a continuous wave radar detection device, a radar and a storage medium.

The invention provides a high-integration-level antenna control system, and belongs to the technical field of antennas. According to the driver, an SOC chip XC7Z045-FFG900 is adopted as a core of a controller. A radio frequency agile transceiver chip AD9361 and a chip PL end are selected to form a receiver unit. The AD9361 chip integrates a zero intermediate frequency architecture in one chip, radio frequency signals from 70MHz to 6GHz can be down-converted to be close to zero frequency, and calculation of signal power can be achieved in cooperation with PL. Meanwhile, the PL end serves as a motor control core, pulse distribution control over six paths of PWM signals of the power inverter circuit is achieved, and therefore the motor is driven to operate continuously, stably and at a high speed. And the chip PS end is responsible for task scheduling, completion and reception of control instructions of the upper computer, real-time data uploading and antenna pointing control.

The invention discloses a residual stress damage identification method and system based on a nonlinear ultrasonic zero-frequency component in the field of ultrasonic early damage detection. The method comprises the following steps: S1, adopting a model without residual stress damage as a standard model; s2, adopting a model containing residual stress damage as a model to be detected; s3, setting a signal excitation point and a signal receiving point at the same position of the standard vertebra model and the to-be-detected model; s4, performing low-pass filtering processing on the signal received by the signal receiving point to extract a zero-frequency signal, and respectively obtaining a standard zero-frequency signal and a damaged zero-frequency signal; s5, calculating and obtaining a difference signal between the damaged zero-frequency signal and the standard zero-frequency signal, and recording the difference signal as a residual zero-frequency signal; s6, damage analysis: judging the type of residual stress damage by utilizing concavity and convexity of the residual zero-frequency signal, and judging the size of the residual stress damage according to the strength of the residual zero-frequency signal; and related difficulties of hybrid wave and second harmonic technologies are overcome.

The application belongs to the technical field of surveying, and provides an improved method for surveying underground water in high-resistance surrounding rock area by using transient electromagnetic method, which comprises the following steps: obtaining high-resistance surrounding rock area, collecting transient electromagnetic data in the high-resistance surrounding rock area, checking whether negative response exists in late channel, introducing Cole-Cole model to carry out forward modeling when the negative response exists, extracting zero-frequency resistivity, charging rate, time constant and frequency correlation coefficient, simultaneously solving zero-frequency resistivity and three induced polarization parameters by using quasi-two-dimensional regularization Newton inversion, and delineating underground water-bearing stratum by joint interpretation of zero-frequency resistivity and three induced polarization parameters. The application is aimed at the negative response of late channel caused by induced polarization effect of underground water in high-resistance surrounding rock area, and can extract zero-frequency resistivity and other three induced polarization parameters by using the negative response, and carry out underground water surveying by using quasi-two-dimensional regularization Newton inversion interpretation.

The application discloses an optical frequency comb locking system for eliminating carrier envelope phase shift frequency, and the disclosed system comprises an optical frequency comb, a repetition frequency detector, a carrier envelope phase shift detector, an attenuator, an operational amplifier, a filter, a power divider, a double balanced mixer, a bias voltage and a phase-locked loop; the system extracts the sum and difference frequencies of the repetition frequency and the carrier envelope phase shift frequency of the optical frequency comb, and locks them to each other, so as to realize the carrier envelope phase shift frequency locking to zero frequency, and reduce the difficulty of the optical frequency comb locking. The application solves the problem of high locking difficulty of the traditional optical frequency comb, simplifies the carrier envelope phase shift frequency control, has the feasibility of productization and high integration, has universality, and can be widely applied to different types of optical frequency comb systems.

The present invention discloses a radar noise floor estimation method, device, storage medium, and terminal device, belonging to the field of radar detection technology. The method comprises: S100, dividing a number of frequency points according to the signal bandwidth occupied by the radar during operation to form a set s; S200, selecting each frequency point in the set s, transmitting and receiving echo signals according to a preset method, and obtaining the corresponding echo signal matrix R t (k); S300, low-frequency filtering and / or DC component suppression are performed on each echo signal matrix, and a fast Fourier transform is performed; S400, all obtained fast Fourier transform sequences are energy-combined to obtain the radar noise floor power. The present invention can concentrate the energy of moving target interference in the environment near zero frequency, filter out the interference through low-frequency filtering and other processing methods, and then fully suppress the moving target interference through fast Fourier transform to estimate the radar noise floor power, thereby improving the efficiency of noise floor estimation.

The invention discloses a zero-frequency signal amplitude reduction method and system based on a multi-cut full-parallel FIR filter, and belongs to the technical field of chip digital design, and the method comprises the steps: executing the CSD multiplication of a filter coefficient and input data, and obtaining a plurality of partial products; carrying out cutting processing on the plurality of partial products respectively; calculating a compensation value of a truncation error based on the symbol attributes of the plurality of partial products and the state of the least significant bit after truncation; and accumulating the plurality of partial products after cutting processing and the compensation value to obtain filtering output. The invention solves the problems that the zero-frequency signal amplitude of the filter is obviously increased and the resource efficiency and the signal precision are difficult to consider at the same time due to the fact that the truncation digits are increased for reducing hardware resources in the prior art.

The present invention provides a GNSS signal capture method and device, the method comprising: sampling the spread spectrum code at 1 / N times the code rate and compressing the length to L, controlling the length of each segment to be L when segmenting satellite data, and mixing with the local carrier to obtain zero-frequency data; searching the NH code phase of the satellite data, stripping the NH code from each segment of data, and performing coherent integration to obtain a compressed satellite signal with a length of 2 spread spectrum cycles; performing FFT operation, complex multiplication and IFFT operation on the processed spread spectrum code and satellite data to obtain a cyclic correlation result; modulo the result and search for the maximum value, if the maximum value exceeds the preset first threshold, it is determined that the rough capture is successful, and the satellite signal code phase, Doppler value and NH code phase are calculated; the code phase is accurately searched at 1 / 2 code chip intervals within a range of N / 2 around the rough capture satellite signal code phase. The method consumes little hardware resources and can improve the capture signal-to-noise ratio and the capture code phase accuracy.

The invention discloses an IQ imbalance calibration method and system. The method comprises pre-calibration and fine calibration. During pre-calibration, firstly, M frequency points are selected in a sectional mode, narrow-band calibration is carried out, correlation factors of amplitude imbalance errors and phase imbalance errors of the multiple frequency points are obtained, interpolation fitting is carried out on zero frequency points, and frequency response characteristics in the whole bandwidth are obtained. On the basis, a solution equation is constructed to calculate a filter coefficient, and a filter is designed to compensate the IQ imbalance error. During fine calibration, based on the least square method, the compensation coefficient of the filter is calculated in a real-time and self-adaptive manner, whether iteration is updated or not is judged, iterative filtering is carried out to enhance the stability of the system, and the problem of calibration performance deterioration caused by environmental factors such as temperature change is effectively solved. Compared with traditional narrowband calibration, the calibration system combining pre-calibration and fine calibration has a calibration effect on receiver large-bandwidth IQ imbalance, the adaptive capacity of the calibration system to environment temperature changes is enhanced, and the calibration precision and robustness are improved.

The invention discloses a rock induced polarization parameter inversion method and device, electronic equipment and a medium. The method comprises the following steps: establishing an MGEMTIP model according to resistivity dispersion, zero frequency resistivity, polarizability and a time constant; judging an induced polarization frequency band based on experimental data, determining a high frequency band, an induced polarization frequency band and a low frequency band, and inputting a true conductivity initial value; calculating a polarizability spectrum; judging whether the low frequency band of the polarizability spectrum meets the condition that eta H is equal to 0 or not; if not, adjusting the initial value of the true conductivity, and repeatedly calculating the polarizability spectrum until eta H is equal to 0; an effective polarizability spectrum is obtained, and then the true conductivity sigma0M0, the IP polarizability and the IP equivalent time constant are calculated according to an MGEMTIP model. The MGEMTIP model is more suitable for complex polarization characterization after superposition of actual rock multi-polarization mechanisms, low-frequency polarization caused by electrode polarization is effectively suppressed or removed, and rock induced polarization features are more accurately and effectively extracted.

The invention provides an orthogonal frequency division multiplexing signal modulation method and system, and belongs to the technical field of wireless communication, and the method comprises the steps: mapping a to-be-transmitted frequency domain data signal and a to-be-transmitted pilot signal to a frequency domain resource grid matrix; performing frequency domain moving operation on each row vector of the frequency domain resource grid matrix, and moving a zero frequency component to a vector center to obtain a moved matrix; and performing inverse fast Fourier transform on each row vector of the moved matrix to obtain a time domain orthogonal frequency division multiplexing symbol matrix as a modulation result. According to the invention, the whole frequency domain resource is constructed into a two-dimensional matrix, and all subsequent signal processing operations take the row vector of the two-dimensional matrix as a basic unit and are completed through a series of clear matrix and vector operation steps. In this way, IFFT calling of a black box for the whole frame is deconstructed into visible and monitorable steps for single symbols, and the problem that the process is not transparent is solved.

This invention discloses an adaptive cancellation circuit for a frequency-modulated continuous wave radar, comprising the following components: a power divider, which splits the radar signal into two output signals, namely a first transmitted signal and a second signal LO; and a mixer, which receives the two output signals from the power divider, one of which serves as the local oscillator and the other as the receiver; the self-coupling signal delay at the RF input port of the mixer is the same as the delay of the second signal LO. This invention increases the LO trace delay, making the LO trace path delay equal to the antenna self-coupling path delay, thereby bringing the self-coupling intermediate frequency (IF) signal output close to zero frequency. This allows the self-coupling IF signal to be easily filtered out, significantly reducing the signal-to-noise ratio degradation caused by the impulse response.

1. Name of the product in this design: Uniaxial zero-frequency sensor. 2. Application of this design: A sensor for high-precision measurement under static or extremely low frequency (near DC) signals. 3. The key design feature of this product is its shape. 4. The image or photograph that best illustrates the design's key points: 3D view 1.

The present application belongs to the field of integrated circuit manufacturing online measurement, and discloses a snapshot overlay error measurement method and system, which comprises the following steps: measuring a measured object, obtaining two measurement spectra with positive and negative preset deviations respectively, coherently demodulating the measurement spectra, and shifting the specific frequency channel to the zero frequency channel; processing the spectrum data after frequency shifting by using a linear operator to obtain the coefficients corresponding to the positive and negative preset deviations; constructing a characteristic quantity according to the linear combination of the real part and the imaginary part of the coefficients, then calculating the corresponding characteristic quantity according to the coefficients corresponding to the positive and negative preset deviations; and calculating the overlay error according to the characteristic quantity based on the linear relationship between the characteristic quantity and the overlay error. The present application can solve the overlay error with multi-wavelength coupling without using traditional Fourier analysis and truncation operation, has high precision and robustness to noise, and can be used for data processing of snapshot overlay error measurement in multiple scenes.

The invention discloses a control method and control module for a Coriolis flowmeter, and the control method comprises the steps: obtaining a vibration signal of the Coriolis flowmeter, carrying out the frequency shift of the vibration signal with the inherent frequency of the Coriolis flowmeter as a target frequency and the zero frequency as an end point frequency, obtaining a frequency shift signal, carrying out the filtering of the frequency shift signal, obtaining a filtering signal, and carrying out the control of the Coriolis flowmeter. Re-sampling the filtered signal to obtain a re-sampled signal, performing FFT calculation on the re-sampled signal to obtain a frequency spectrum of the re-sampled signal, and performing frequency mapping on the frequency spectrum of the re-sampled signal to obtain a first frequency spectrum of the vibration signal. The frequency spectrum of the inherent frequency section of the Coriolis flowmeter is refined, the resolution of the frequency band is improved, the frequency detection precision is effectively improved, and the method is particularly suitable for processing complex signals or narrow-band signals. While the computing power is saved, a finer and more accurate signal frequency spectrum can be obtained, the phase difference calculation precision can be improved, and the excitation signal can be adjusted.

The invention discloses a frequency-stabilized phase-locked intermediate infrared single-cavity double-comb measurement system and method, and solves the problems of complex system structure and huge size caused by the need of ultra-stable external optical / microwave reference, pumping broadband servo locking, high-frequency precise electric control loop and the like in the conventional double-comb measurement system. According to the invention, a homologous pumping single-cavity double-comb architecture is adopted, and an innovative mechanism of eliminating pumping frequency and zero frequency offset by combining optical and electrical frequency mixing is adopted, so that complex means such as reference frequency locking, repetition frequency and carrier envelope offset frequency detection required by a traditional scheme are not needed, and the method has the advantages of being easy to construct and simple and convenient to operate.

The invention discloses a method for measuring the internal temperature of a high-temperature solid based on a nonlinear ultrasonic zero-frequency signal, which belongs to the technical field of nondestructive measurement and comprises the following steps of: firstly, exciting ultrasonic waves on one side of a solid structure by a solid material under different uniform temperature field conditions, receiving an ultrasonic signal on the other side of the solid structure, and processing the signal to obtain an ultrasonic signal; the amplitudes of the nonlinear ultrasonic zero-frequency signals in different uniform temperature fields are observed and recorded; then, determining the incidence relation between the amplitude of the nonlinear ultrasonic zero-frequency signal and the temperature; and after the incidence relation between the amplitude of the non-linear ultrasonic zero-frequency signal and the temperature is determined, in subsequent ultrasonic detection, the internal temperature of the solid structure is obtained by combining the incidence relation between the amplitude of the non-linear ultrasonic zero-frequency signal and the temperature. The method is not limited to the type of solid materials, stable measurement can be achieved in the high-temperature or extremely-high-temperature environment, the sensitivity is far higher than that of linear ultrasonic parameters, and the real-time performance is good.

The present application relates to the technical field of ammeter self-calibration, and specifically to a measurement self-calibration method and system for a clamp ammeter, the method comprising: comparing the difference between the amplitude of each smoothed current signal at zero frequency in the frequency domain and the mean amplitude at all frequencies to determine the first filtered residual value of each smoothed current signal; determining the confidence level of each smoothed current signal by analyzing the similarity between each smoothed current signal and a standard current calibration signal, and combining the first filtered residual value; obtaining the error correction coefficient of each smoothed current signal, and combining the confidence level to self-calibrate the measurement of the clamp ammeter at the current moment. The present application solves the problems of harmonic distortion generated by nonlinear load devices and circuits, and interference with the calculation accuracy of the error correction coefficient of the clamp ammeter caused by the DC component introduced by the load current, thereby improving the self-calibration accuracy of the clamp ammeter.