CN103852444A - Calibration-free modulation spectrum measuring system - Google Patents

Abstract

The invention establishes a calibration-free modulation spectrum measuring software system based on a tunable diode laser absorption spectrum by virtue of a wavelength modulation technique adapted to a severe environment. The system comprises a digital phase-locking signal demodulation module, a modulation spectrum simulation module and a measured parameter extraction module which comprise 14 sub-modules. The system has the specific functions that a photoelectric signal is demodulated by virtue of a digital phase-locking algorithm so as to obtain a harmonic signal; a simulation database of the harmonic signal can be obtained by carrying out accurate theoretical calculation; the speed, temperature and constituent concentration of a flow field can be extracted by combining the harmonic signal with the simulation database.

Description

Non-calibrating modulated spectrum measuring system

Technical field

The invention belongs to field of optical measuring technologies, relate to the methods such as signal processing and numerical simulation, general, the reliable measurements system of measuring exploitation for the absorption spectrum of gas molecule in space are provided.

Background technology

Optical measuring technique has obtained application more and more widely in fields such as scientific experiment, environmental monitoring and combustion field diagnosis.Intensity signal before absorption spectrum needs to measure absorption in theory simultaneously and after absorbing could obtain the absorption information of molecule.In actual applications, often adopt the method such as reference beam or Function Fitting to determine the light intensity before absorbing, i.e. spectrum baseline.These methods are difficult to obtain spectrum baseline information accurately.In addition, although modulator approach can significantly improve the signal to noise ratio (S/N ratio) of measuring-signal, many-sided factor analysis such as the signal intensity of modulated spectrum and depth of modulation, spectral line line style and intensity modulated, therefore the quantitative measurment of modulated spectrum also has difficulties always.

The K.H.Lyle of Stanford Univ USA, the people such as R.K.Hanson, once utilized modulated spectrum to strengthen the signal to noise ratio (S/N ratio) of aeromotor air intake duct oxygen absorption spectral measurement.Due to the quantitative corresponding relation not solving in theory between modulated spectrum intensity and linear function, only carry out measuring speed with the center of spectrum peak herein, the measurement of concentration realizes by direct absorption spectrum.After this, G.B.Rieker has analyzed the principle that Wavelength modulation spectroscopy is measured theoretically, has provided the expression formula of harmonic signal, weight analysis and has measured possible source of error.After studies show that and utilizing 1f signal normalization 2f signal, can realize the measurement under any pressure, concentration and temperature conditions by theoretical simulation accurately.Verify the measurement result of hydrone and gas concentration lwevel and combustion field temperature, shown that Wavelength modulation spectroscopy improves approximately 4 times than direct absorption spectrum signal to noise ratio (S/N ratio).The document does not propose detailed implementation method, and the feasibility that modulated spectrum is measured has only been discussed.

The people such as the Li Ning of Institutes Of Technology Of Nanjing, adopt the method for emulation to obtain harmonic signal theoretical value, utilize second harmonic peak valley recently to eliminate initial light intensity and the impact of detector gain on signal intensity.Because crest and trough do not occur in time simultaneously, when in measuring process when initial light-intensity variation, crest, the initial light intensity that trough is corresponding are not identical, can not eliminate its impact on signal.In addition, the method must scan and obtain complete harmonic signal and could extract crest and trough information, serious or occur when overlapping, being often difficult to realize for spectral line broadening.Tsing-Hua University's Thermal Power Engineering is the people such as Che Lu, has studied and has utilized odd harmonics signal reconstruction absorption spectra line style.By absorption line shape being carried out to Fourier series and Taylor series analysis, obtain the relation of linear function and odd harmonics, and under laboratory condition, verified the measurement of concetration of ammonia.In the method, the intensity of harmonic signal is still relevant to initial light intensity.Although initial light intensity can be measured in advance, under the environment of serious interference, the decay that many non-absorption factors cause causes initial light intensity in measuring process, to occur significantly changing, and now measurement result will occur serious deviation.Therefore the method does not really realize non-calibrating measurement, can only under laboratory condition, apply.

The present invention is based on tunable diode laser absorption spectroscopy (tunable diode laser absorption spectroscopy, TDLAS) technology, a kind of non-calibrating modulated spectrum measuring system is provided, not only utilize the advantage of modulated spectrum, and having solved theoretically the problem of spectrum baseline extraction, the non-calibrating that can realize is truly measured.

Summary of the invention

The invention provides a kind of non-calibrating modulated spectrum measuring system, the non-calibrating truly of realizing based on tunable diode laser absorption spectroscopy technology is measured.It is characterized in that:

(1) digital phase-locking phase signals demodulation module comprises that measuring-signal gathers submodule, restituted signal generates submodule, filtering parameter input submodule, digital mixing calculating sub module, low-pass filter generation submodule, low-pass filtering operator module; Wherein, measuring-signal gathers submodule, is read and is surveyed photosignal, sample rate f by data acquisition equipment ₁with data length L; Restituted signal generates submodule, according to modulating frequency f, sample rate f ₁with data length L, the reference signal that generating solution calls, comprises frequency multiplication sine and a cosine signal, and two frequency multiplication sine and cosine signals; Filtering parameter input submodule, for creating the interactive interface of user and program, by low-pass cut-off frequencies and the filtering order of keyboard input filter; Digital mixing calculating sub module, multiplies each other a frequency multiplication sine, cosine signal and two frequency multiplication sines, cosine signal respectively with carrier signal, obtain four road mixed frequency signals; Low-pass filter generates submodule, according to proportion f ₁, low-pass cut-off frequencies and filtering order, create low-pass filtering algorithm; Low-pass filtering operator module, will obtain Si road mixed frequency signal and pass through respectively digital filter computing, obtain the X component (X of first harmonic signal _1f) and Y component (Y _1f), and the X component (X of second harmonic _2f) and Y component (Y _2f), and calculate respectively R amount;

(2) modulated spectrum emulation module comprises that laser parameter input submodule, line parameters input submodule, linear function calculating sub module, harmonic signal calculating sub module, simulation data base build submodule; Wherein, laser parameter input submodule, inputs or read data files by keyboard, for harmonic signal simulation calculation provides laser parameter; Line parameters input submodule, inputs or read data files by keyboard, for harmonic signal simulation calculation provides line parameters; Linear function calculating sub module, carries out numerical integration calculating to the line parameters of input, obtains linear function; Harmonic signal calculating sub module, utilizes the laser parameter of input and the linear function calculating, and calculates harmonic signal; Simulation data base builds submodule, by calculating the harmonic signal that different laser parameters and line parameters are corresponding, obtains simulation data base;

(3) measurement parameter extraction module comprises that velograph operator module, signal height extraction submodule, temperature, concentration solve submodule; Wherein, velograph operator module, for extracting Doppler shift amount the computational flow speed of harmonic signal; Signal height is extracted submodule, obtains the height value of harmonic signal by extracting the maximal value of harmonic signal; Temperature, concentration solve submodule, by the iterative algorithm height value of emulation harmonic signal and the height value of experiment harmonic signal, solve temperature and the concentration in flow field.

The present invention utilizes unique data processing method and numerical simulation accurately, has solved the problem of modulated spectrum quantitative measurment.Because algorithm function is complete, simplify the demand of measuring hardware, tool has the following advantages:

(1) digital phase-locking phase signals demodulation part has not only substituted lock-in amplifier, and has expanded its function.Numeral phase locked algorithm has been realized the repertoire of the lock-in amplifier such as carrier wave and reference signal mixing and low-pass filtering, also has the irrealizable function of hardware.The restriction that numeral phase locked algorithm is not subject to modulating frequency, can realize the signal demodulation of optional frequency in principle; Algorithm can unconfined extended channel quantity, the harmonic signal of the higher order of demodulation.Utilize Digital Filtering with Zero Phase Error algorithm to solve the phase delay problem that low-pass filtering is brought simultaneously.

(2) non-calibrating of having realized Wavelength modulation spectroscopy is measured.Modulated spectrum emulation part, utilizes first harmonic to return signal one to change second harmonic signal, eliminates the impact of initial light intensity on harmonic signal intensity, has realized non-calibrating measurement in principle.This part is from the fundamental equation of absorption spectrum, calculates harmonic signal, for experiment measuring provides correlative value by theoretical model accurately.

(3) create a kind of algorithm of uniqueness, solved the problem that three dimensions search is separated.Solve the corresponding relation between temperature, concentration and harmonic signal aspect ratio by iteration, reduced simulation calculation amount.

Brief description of the drawings

Fig. 1 is the module composition frame chart of non-calibrating modulated spectrum measuring system of the present invention;

Fig. 2 is linear function of the present invention and harmonic wave signal simulation schematic diagram;

Fig. 3 is the schematic diagram that is related to of harmonic signal of the present invention and aspect ratio and temperature;

Fig. 4 is harmonic signal Doppler shift extraction algorithm schematic diagram of the present invention;

Fig. 5 is temperature of the present invention, concentration iterative algorithm flow chart.

Specific embodiments

With case study on implementation, non-calibrating modulated spectrum measuring system of the present invention is described in further detail by reference to the accompanying drawings.Fig. 1 has provided program module composition block diagram of the present invention.

Measuring system of the present invention is totally divided into three modules, i.e. digital phase-locking phase signals demodulation module, modulated spectrum emulation module and measurement parameter extraction module.Each module has relatively independent function and compatible IO interface, conveniently calls and transplants.

Non-calibrating modulated spectrum measuring system of the present invention, implementation step is as follows:

Step 1, set up software platform

Described measuring system, based on LabVIEW Development of Software Platform, realizes signals collecting, processing, the functions such as simulation modeling, image processing.The first step is the version of installing on computers more than LabVIEW8.5.

Step 2, task module distribute

Described measuring method comprises three modules, i.e. digital phase-locking phase signals demodulation, modulated spectrum emulation and measurement parameter extract.Be divided into 14 submodules: measuring-signal gathers submodule (1), restituted signal generates submodule (2), filtering parameter input submodule (3), digital mixing calculating sub module (4), low-pass filter generates submodule (5), low-pass filtering operator module (6), laser parameter input submodule (7), line parameters input submodule (8), linear function calculating sub module (9), harmonic signal calculating sub module (10), simulation data base builds submodule (11), velograph operator module (12), signal height is extracted submodule (13), temperature, concentration solves submodule (14).All submodules, according to its logical relation combination, are obtained to non-calibrating modulated spectrum measuring system.

Step 3, the exploitation of each submodule

To each submodule stand-alone development of non-calibrating modulated spectrum measuring system, connected module adopts unified data input/output format in logic, and each module embodiment is as follows:

1., measuring-signal collection (1)

Measuring-signal gathers submodule, is read and is surveyed photosignal, sample rate f by data acquisition equipment (as data collecting card) ₁with data length L.Surveying photosignal is the high-frequency carrier signal through ovennodulation, the information that has comprised tested flow field.Sample rate f ₁be passed to restituted signal with data length L and generate submodule (2).In order to save data traffic and storage space, clean carrier signal can adopt shaping form according to analog digital conversion (ADC) figure place of capture card.For example, data collecting card adopts NI-PCI6115, and ADC is 12, be set as ± 1V of full scale.Data can adopt 12 or 16(16 position comparatively general) bit strip symbol shaping form, integer+2047(2 in data ¹¹-1) representation signal is 1V.Software default real number is 64 for double precision formats, adopts 16 can save 3/4 storage space for shaping form.The data input of this module comprises sample rate f ₁with data length L, data output comprises sample rate f ₁, data length L and carrier signal.

2., restituted signal generates (2)

This submodule is according to modulating frequency f, sample rate f ₁with data length L, the reference signal that generating solution calls, comprises frequency multiplication sine and a cosine signal, and two frequency multiplication sine and cosine signals.The sampling rate of reference signal is identical with detectable signal with data length, and signal frequency equals modulating frequency.The data input of this module comprises sample rate f ₁, data length L and modulating frequency f, data output comprises four one-dimension array.

3., filtering parameter input (3)

The function of this module is to create the interactive interface of user and program, by low-pass cut-off frequencies and the filtering order of keyboard input filter.This module and low-pass filter generation module are separated, and are the transplanting in order to facilitate the latter.

4., digital mixing calculates (4)

Digital mixing calculating sub module, is equivalent to the frequency mixer in lock-in amplifier, multiplies each other by carrier signal and reference signal.In order to solve the X component (X of first harmonic signal _1f) and Y component (Y _1f), and the X component (X of second harmonic _2f) and Y component (Y _2f), a frequency multiplication sine, cosine signal and two frequency multiplication sines, cosine signal need to be multiplied each other with carrier signal respectively, obtain four road mixed frequency signals.Because reference signal and carrier signal have identical sampling rate and length, therefore by carrier signal array and reference signal array point-to-point multiplying each other respectively.

5., low-pass filter generates (5)

According to proportion f ₁, low-pass cut-off frequencies and filtering order, create low-pass filtering algorithm, i.e. low-pass filter.This method adopts Butterworth (Butterworth) wave filter, because its amplitude-response curve has the most smooth characteristic in passband, and amplitude-response curve is monotone variation in passband and stopband.

6., low-pass filtering computing (6)

To obtain Si road mixed frequency signal and pass through respectively digital filter computing, obtain the X component (X of first harmonic signal _1f) and Y component (Y _1f), and the X component (X of second harmonic _2f) and Y component (Y _2f).And calculate respectively R and measure.Introduce and adopt Zero-phase Digital Filter algorithm, harmonic carcellation signal is drawn to filtering and the phase delay that produces, specific practice be by mixed frequency signal filtering operation, oppositely, filtering operation, again reverse again.

7., laser parameter input (7)

The function of this submodule is for harmonic signal simulation calculation provides laser parameter, and laser parameter can be inputted or read data files by keyboard.Input parameter comprises: normalized intensity modulation amplitude i ₀, laser frequency depth of modulation a, and phase delay Ψ between intensity modulated and frequency modulation (PFM).These parameters measure by testing in advance.

8., line parameters input (8)

The function of this submodule is for harmonic signal simulation calculation provides line parameters, and line parameters can be inputted or read data files by keyboard.Input parameter comprises: room temperature line strength, low state energy and, spectral line air collision broadening and self collision widen coefficient and humidity index.

9., linear function calculates (9)

The absorption spectrum linear function of gas molecule in space is described with Voigt linear function conventionally, and Voigt linear function is the convolution of Gauss linear function and Lorentz linear function, there is no analytic solution, can only calculate by numerical integration.

10., harmonic signal calculates (10)

Harmonic signal calculating sub module is the core of numerical simulation part, its objective is according to theory and calculates under specified pressure, concentration, temperature conditions, the harmonic signal of a certain spectral line.Harmonic signal is not only relevant with test environment, also relevant with line parameters and laser parameter, sets up theoretical model accurately, is the basis of temperature and measurement of concetration.

When laser is the uniform dielectric of L through distance, light intensity propagation distance is exponential damping, can be represented by Beer-Lambert law:

$\ln \left(\frac{I_t}{I_0}\right)={-k}_{v}L={-\mathrm{PS}}_{\mathrm{vi}}\left(T\right)\mathrm{\Φ}\left(v\right)\mathrm{\χL}---\left(1\right)$

Wherein I _tand I ₀respectively laser incident and transmitted light intensity, k _νbe spectral absorptance, P is gas stagnation pressure, and χ is gas component concentrations to be measured, and Φ is linear function, and ν is laser frequency, S _{ν i}(T) be spectral line ν used _iline strength in the time of temperature T.Conventionally by modulating Distributed Feedback Laser Injection Current to change sharp light frequency, the light intensity of laser instrument transmitting simultaneously also changes thereupon, i.e. I in equation (1) ₀for non-definite value.

In scanning spectral line, with high-frequency signal modulated laser wavelength, measure its harmonic signal and complete, be i.e. Wavelength modulation spectroscopy.The Injection Current of laser instrument is subject to Sine Modulated, and laser frequency can be write as:

$v\left(t\right)=\stackrel{\‾}{v}+a\cos (2\mathrm{\πft}+{\mathrm{\ψ}}_1)---\left(2\right)$

Wherein

be laser instrument centre frequency, a is depth of modulation.Beer-Lambert law is rewritten into:

$I_t\left(t\right)\stackrel{\‾}{I_0}\left(t\right)(1+i_0\cos (2\mathrm{\πft}+{\mathrm{\ψ}}_2))e^{-\mathrm{\α}(\stackrel{\‾}{v}\left(t\right)+a\cos (2\mathrm{\πft}+{\mathrm{\ψ}}_1))}---\left(3\right)$

Wherein

average laser power, i ₀be normalization intensity modulation amplitude, ψ is the phase differential of frequency modulation (PFM) and intensity modulated.Equation (3) exponential part has reflected molecule absorption information, is carried out Fourier expansion, can be expressed as:

$\begin{array}{c}\exp [-\mathrm{\α}(\stackrel{\‾}{v}+a\cos \left(2\mathrm{\πft}\right))]=\underset{k=0}{\overset{\∞}{\mathrm{\Σ}}}{H}_k(\stackrel{\‾}{v},a)\cos \left(2\mathrm{\πft}\right)\\ H_0(\stackrel{\‾}{v},a)=\frac{1}{2\mathrm{\π}}{\∫}_{-\mathrm{\π}}^{\mathrm{\π}}\exp \left[{-P}_{i}L\underset{j}{\mathrm{\Σ}}{S}_j{\mathrm{\φ}}_j(\stackrel{\‾}{v}+a\cos \left(\mathrm{\ξ}\right))\right]\mathrm{d\ξ}\\ H_k(\stackrel{\‾}{v},a)=\frac{1}{\mathrm{\π}}{\∫}_{-\mathrm{\π}}^{\mathrm{\π}}\mathrm{ecp}\left[{-P}_{i}L\underset{j}{\mathrm{\Σ}}{S}_j{\mathrm{\φ}}_j(\stackrel{\‾}{v}+a\cos \left(\mathrm{\ξ}\right))\right]\cos \left(\mathrm{k\ξ}\right)\mathrm{d\ξ}\end{array}---\left(4\right)$

Transmitted light intensity is subject to modulation and molecule absorption acting in conjunction, first harmonic (R _1f), second harmonic (R _2f) signal indication is:

$\begin{array}{c}{\mathrm{<figure-callout\; id="1f"\; label="R"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">R</figure-callout>}}_{1f}=\sqrt{{\mathrm{<figure-callout\; id="1f"\; label="X"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">X</figure-callout>}}_{1f}^2+{\mathrm{<figure-callout\; id="1f"\; label="Y"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">Y</figure-callout>}}_{1f}^2}\\ {\mathrm{<figure-callout\; id="1f"\; label="X"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">X</figure-callout>}}_{1f}=\frac{G\stackrel{\&OverBar;}{I_0}}{2}[{\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="HDA0000478771080000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_1+i_0({\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">H</figure-callout>}}_0+\frac{H_2}{2})\cos \mathrm{\&Psi;}]\\ {\mathrm{<figure-callout\; id="1f"\; label="Y"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">Y</figure-callout>}}_{1f}=-\frac{G\stackrel{\&OverBar;}{I_0}}{2}\left[i_0(H_0-\frac{H_2}{2})\sin \mathrm{\&Psi;}\right]\end{array}---\left(5\right)$

$\begin{array}{c}{R}_{2f}=\sqrt{X_{2f}^2+Y_{=2f}^2}\\ X_{2f}=\frac{G\stackrel{\&OverBar;}{I_0}}{2}[H_2+\frac{{\mathrm{<figure-callout\; id="0"\; label="i"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">i</figure-callout>}}_0}{2}({\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="HDA0000478771080000011.png"\; state="\{\{state\}\}">H</figure-callout>}}_1+H_3)\cos \mathrm{\&Psi;}]\\ Y_{2f}=-\frac{G\stackrel{\&OverBar;}{I_0}}{2}\left[\frac{{\mathrm{<figure-callout\; id="0"\; label="i"\; filenames="HDA0000478771080000012.png"\; state="\{\{state\}\}">i</figure-callout>}}_0}{2}(H_1-H_3)\sin \mathrm{\&Psi;}\right]\end{array}---\left(6\right)$

Linear function under certain condition and 2f/1f signal are as shown in Figure 2.

, simulation data base build (11)

Under laser parameter and the definite condition of line parameters, harmonic signal is the function of temperature and concentration.In modulated spectrum, temperature is to determine by the intensity ratio of two spectral line harmonic signals, and concentration is determined by the harmonic signal intensity of known temperature bar.Simulation data base is the data set of harmonic signal strength ratio and temperature and concentration corresponding relation just, as shown in Figure 3.Because complete database is three-dimensional (harmonic signal aspect ratio, temperature and concentration), in order to reduce the data volume of database and solving precision to be provided, each emulation obtains harmonic signal aspect ratio, temperature, obtains finally temperature and concentration accurately by iteration emulation.

, speed calculate (12)

The task of velograph operator module is, by T/F corresponding relation, the time axis conversion of harmonic signal is become to frequency axis, then extracts Doppler shift, finally according to light intersection angle calculation gas velocity.For the difference on the frequency between Obtaining Accurate harmonic signal, first harmonic signal is done to standardization processing according to maximal value and both sides minimal value between 0～1; Half-and-half high above signal carries out contour interpolation, the frequency values of picked up signal intensity identical point; The difference on the frequency of the contour point of rising edge and negative edge is averaging, and is the Doppler shift of whole harmonic signal.Doppler shift leaching process is shown in Fig. 4.

, signal height extract (13)

In modulated spectrum, the height correlation of temperature and concentration information and harmonic signal, solves the height that temperature and concentration need accurately to extract by suitable algorithm before harmonic signal.Owing to having passed through low-pass filtering, harmonic signal is more smooth, and harmonic signal height is got maximal value.

, temperature, concentration solve (14)

Under laser parameter and the definite condition of line parameters, harmonic signal is the function of temperature and concentration.In modulated spectrum, temperature is to determine by the intensity ratio of two spectral line harmonic signals, and concentration is determined by the harmonic signal intensity of known temperature bar.If set up the three-dimensional data base of harmonic signal aspect ratio about temperature and concentration, can in database, search temperature and concentration value by measuring-signal.But cause like this sharp increase of database data amount, need the incremental change of temperature and concentration much smaller than experimental error because accurately solve.The algorithm solving is, sets initial concentration, sets up the corresponding relation of harmonic signal aspect ratio and temperature, and inquiry aspect ratio obtains temperature; Ask concentration by temperature harmonic signal height, and revise initial concentration, this process of iteration is until concentration and temperature convergence.Temperature and concentration solve flow process and see Fig. 5.

Step 4, harmonic signal and database to modulated spectrum carry out numerical simulation

After each module coupling debugging, input necessary parameter for program, comprise low-pass filtering parameter, laser parameter, line parameters and laser frequency-time calibration curve.Laser parameter comprises: normalized intensity modulation amplitude i ₀, laser frequency depth of modulation a and phase delay Ψ.Line parameters comprises: room temperature line strength, low state energy and, spectral line air collision broadening and self collision widen coefficient and humidity index., spectral line linear function and a corresponding harmonic signal (R _2f/1f) simulation result see Fig. 2, the simulation result of two spectral line harmonic signals and their aspect ratios is shown in Fig. 3.

The mode of operation of step 5, non-calibrating modulated spectrum measuring system is selected

Need initialization system mode of operation according to measurement, measure in real time or off-line data processing.Surveyingpin is to the measurement below 10Hz in real time, and data processing needs 0.1s.Measure in real time the work of setting data acquisition and processing part parallel, utilize acquisition time to complete the processing of last data.Off-line data tupe, setting data collection and memory module concurrent working.

Claims (1)

1. a non-calibrating modulated spectrum measuring system, comprises digital phase-locking phase signals demodulation module, modulated spectrum emulation module and measurement parameter extraction module, it is characterized in that:

(1) digital phase-locking phase signals demodulation module comprises that measuring-signal gathers submodule, restituted signal generates submodule, filtering parameter input submodule, digital mixing calculating sub module, low-pass filter generation submodule, low-pass filtering operator module.Wherein,

Measuring-signal gathers submodule, is read and is surveyed photosignal, sample rate f by data acquisition equipment ₁with data length L;

Restituted signal generates submodule, according to modulating frequency f, sample rate f ₁with data length L, the reference signal that generating solution calls, comprises frequency multiplication sine and a cosine signal, and two frequency multiplication sine and cosine signals;

Filtering parameter input submodule, for creating the interactive interface of user and program, by low-pass cut-off frequencies and the filtering order of keyboard input filter;

Digital mixing calculating sub module, multiplies each other a frequency multiplication sine, cosine signal and two frequency multiplication sines, cosine signal respectively with carrier signal;

Low-pass filter generates submodule, according to sample frequency f ₁, low-pass cut-off frequencies and filtering order, create low-pass filtering algorithm;

Low-pass filtering operator module, will obtain Si road mixed frequency signal and pass through respectively digital filter computing, obtain the X component (X of first harmonic signal _1f) and Y component (Y _1f), and the X component (X of second harmonic _2f) and Y component (Y _2f), and calculate respectively R amount;

(2) modulated spectrum emulation module comprises that laser parameter input submodule, line parameters input submodule, linear function calculating sub module, harmonic signal calculating sub module, simulation data base build submodule.Wherein,

Laser parameter input submodule, inputs or read data files by keyboard, for harmonic signal simulation calculation provides laser parameter;

Line parameters input submodule, inputs or read data files by keyboard, for harmonic signal simulation calculation provides line parameters;

Linear function calculating sub module, carries out numerical integration calculating to the line parameters of input, obtains linear function;

Harmonic signal calculating sub module, utilizes the laser parameter of input and the linear function calculating, and calculates harmonic signal;

Simulation data base builds submodule, by calculating the harmonic signal that different laser parameters and line parameters are corresponding, obtains simulation data base;

(3) measurement parameter extraction module comprises that velograph operator module, signal height extraction submodule, temperature, concentration solve submodule.Wherein,

Velograph operator module, for extracting Doppler shift amount the computational flow speed of harmonic signal;

Signal height is extracted submodule, obtains the height value of harmonic signal by extracting the maximal value of harmonic signal;

Temperature, concentration solve submodule, by the iterative algorithm height value of emulation harmonic signal and the height value of experiment harmonic signal, solve temperature and the concentration in flow field.

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