Continuous wavelet transform wavelength modulation spectrum harmonic extraction method based on prior knowledge

Abstract

The invention provides a continuous wavelet transform wavelength modulation spectrum harmonic extraction method based on prior knowledge, and relates to the field of gas measurement, spectral analysis and data processing. Aiming at a wavelength modulation spectrum (WMS) harmonic extraction process, the method mainly comprises the following steps: inputting a measurement parameter into a WMS physical model to obtain a theoretical transmittance signal, and obtaining a theoretical harmonic through Fourier transform frequency selection; converting the theoretical harmonic wave to enable the theoretical harmonic wave to meet a permissible condition of a continuous wavelet transform (CWT) mother wavelet function, and obtaining a mother wavelet function based on priori knowledge; according to the method, a primary wavelet function based on priori knowledge is modulated by using a shift strategy to obtain a secondary wavelet function, the secondary wavelet function is used as a convolution kernel to process a transmitted light signal to obtain a target harmonic, and on the basis of the scheme, the method realizes rapid and high signal-to-noise ratio extraction of the target harmonic, so that the precision and stability of gas measurement are improved.

Description

Technical Field

[0001] The present application relates to the fields of gas measurement, spectral analysis and data processing, and in particular to a method and device for extracting harmonics from a continuous wavelet transform wavelength modulation spectrum based on prior knowledge. Background Art

[0002] Tunable diode laser absorption spectroscopy (TDLAS) has been widely used in industry due to its non-invasive, high sensitivity and ability to measure a variety of gases. Among them, wavelength modulation spectroscopy (WMS) applies a modulation signal to the laser to increase the effective information to the high-frequency harmonic region, and then inverts the gas parameters by harmonic extraction, thereby achieving the purpose of suppressing the 1 / F noise of lasers, detectors and other equipment in the measurement system. WMS is widely used in industrial production, medical testing, atmospheric sensing, basic experimental spectroscopy, combustion diagnosis and other fields because of its higher signal-to-noise ratio and lower detection limit. However, in WMS, the current traditional harmonic extraction method uses a traditional bandpass filter, which cannot distinguish the noise with the same frequency as the gas absorption harmonic. In addition, the optimization of the filter parameters is time-consuming, which increases the complexity of the measurement algorithm and reduces the robustness to the measurement parameters (modulation coefficient). Summary of the invention

[0003] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0004] To this end, the first purpose of this application is to propose a continuous wavelet transform wavelength modulation spectrum harmonic extraction method based on prior knowledge, which reduces the optimization time of filter parameters, simplifies the harmonic extraction process, improves the robustness of measurement parameters, and reduces the detection limit of measurement while improving the signal-to-noise ratio of harmonics.

[0005] The second objective of the present application is to propose a harmonic extraction device of continuous wavelet transform wavelength modulation spectrum based on prior knowledge.

[0006] To achieve the above-mentioned purpose, the first embodiment of the present application proposes a method for extracting harmonics by continuous wavelet transform wavelength modulation spectroscopy based on prior knowledge, which is used to extract harmonic signals when measuring gas by TDLAS technology and wavelength modulation spectroscopy WMS technology. The method includes:

[0007] The measurement parameters are input into the WMS physical model to obtain the theoretical transmittance signal, and the theoretical harmonics are obtained through Fourier transform frequency selection;

[0008] The theoretical harmonics are transformed to satisfy the admissible conditions of the CWT mother wavelet function, and the mother wavelet function based on prior knowledge is obtained;

[0009] Using the shift strategy, the mother wavelet function based on prior knowledge is modulated to obtain a daughter wavelet function, and the daughter wavelet function is used as the CWT filter convolution kernel to process the transmitted light signal to obtain the target harmonic.

[0010] Optionally, in one embodiment of the present application, the measurement parameters include modulation coefficient, scanning coefficient, collision broadening, Doppler broadening, modulation frequency and scanning frequency.

[0011] Optionally, in one embodiment of the present application, the measurement parameters are input into the WMS physical model to obtain a theoretical transmittance signal, including:

[0012] The measured parameters are input into the WMS physical model, and the simulated harmonics are output, where the simulated harmonics are expressed as:

[0013]

[0014] Among them, X 2 and Y 2 represents the vertical phase-locked decomposition result of 2f, G opt is the photoelectric gain, I 1,M is the modulation amplitude of the laser intensity, is the average value of the laser output intensity, φ 1,M is the phase angle of wavelength modulation, H k is the frequency kf m The complex Fourier coefficient of the transmission intensity, H 1 , H 3 For distortion.

[0015] Optionally, in one embodiment of the present application, the theoretical harmonic H 2 The permissible conditions of the CWT mother wavelet function satisfied after the transformation are:

[0016]

[0017] ∫ |t|<T dt|ψ(t)| 2 ≥(1-ε)||ψ(t)|| 2

[0018] ∫ψ(t) 2 dt=1

[0019] ∫ψ(t 1 )ψ(t 2 )dt=δ(t 1 ,t 2 )

[0020] Among them, ω is the frequency, ε is an arbitrary small quantity, t is the time, ψ(ω) is the frequency domain expression of the wavelet function, ψ(t) is the time domain expression of the wavelet function, and δ(,) is the impulse function.

[0021] Optionally, in one embodiment of the present application, a shift strategy is used to modulate a mother wavelet function based on prior knowledge to obtain a daughter wavelet function, including:

[0022] By using Modulate the sub-wavelet functions and adjust the center frequency independently so that the frequency scale a is optimized according to the shape of the target harmonics;

[0023] The modulation process is expressed as:

[0024]

[0025] in, is the time domain expression of the daughter wavelet function, ψ(at-b) is the mother wavelet function, j is a unit imaginary number, W DWF is the sub-wavelet bandwidth, W MWF is the mother wavelet bandwidth, C DWF is the sub-wavelet center frequency, C MWF is the center frequency of the mother wavelet, ω c is the shift frequency.

[0026] To achieve the above-mentioned purpose, the second aspect of the present invention proposes a continuous wavelet transform wavelength modulation spectrum harmonic extraction device based on prior knowledge, which is used to realize harmonic signal extraction when gas measurement is performed using TDLAS technology and wavelength modulation spectrum WMS technology. The device includes:

[0027] A priori knowledge module is used to input the measurement parameters into the WMS physical model to obtain the theoretical transmittance signal and obtain the theoretical harmonics through Fourier transform frequency selection;

[0028] Improved CWT module is used to transform theoretical harmonics to satisfy the admissible conditions of CWT mother wavelet function, obtain mother wavelet function based on prior knowledge, and use shift strategy to modulate mother wavelet function based on prior knowledge to obtain daughter wavelet function.

[0029] The harmonic extraction module is used to process the transmitted light signal using the sub-wavelet function as the CWT filter convolution kernel to obtain the target harmonic.

[0030] Optionally, in one embodiment of the present application, the measurement parameters include modulation coefficient, scanning coefficient, collision broadening, Doppler broadening, modulation frequency and scanning frequency.

[0031] Optionally, in one embodiment of the present application, the measurement parameters are input into the WMS physical model to obtain a theoretical transmittance signal, including:

[0032] The measured parameters are input into the WMS physical model, and the simulated harmonics are output, where the simulated harmonics are expressed as:

[0033]

[0034] Among them, X 2 and Y 2 represents the vertical phase-locked decomposition result of 2f, G opt is the photoelectric gain, I 1,M is the modulation amplitude of the laser intensity, is the average value of the laser output intensity, φ 1,M is the phase angle of wavelength modulation, H k is the frequency kf m The complex Fourier coefficient of the transmission intensity, H 1 , H 3 For distortion.

[0035] Optionally, in one embodiment of the present application, the theoretical harmonic H 2 The permissible conditions of the CWT mother wavelet function satisfied after the transformation are:

[0036]

[0037] ∫ |t|＜T dt|ψ(t)| 2 ≥(1-ε)||ψ(t)|| 2

[0038] ∫ψ(t) 2 dt=1

[0039] ∫ψ(t 1 )ψ(t 2 )dt=δ(t 1 ,t 2 )

[0040] Among them, ω is the frequency, ε is an arbitrary small quantity, t is the time, ψ(ω) is the frequency domain expression of the wavelet function, ψ(t) is the time domain expression of the wavelet function, and δ(,) is the impulse function.

[0041] Optionally, in one embodiment of the present application, a shift strategy is used to modulate a mother wavelet function based on prior knowledge to obtain a daughter wavelet function, including:

[0042] By using Modulate the sub-wavelet functions and adjust the center frequency independently so that the frequency scale a is optimized according to the shape of the target harmonics;

[0043] The modulation process is expressed as:

[0044]

[0045] in, is the time domain expression of the daughter wavelet function, ψ(at-b) is the mother wavelet function, j is the unit imaginary number W DWF is the sub-wavelet bandwidth, W MWF is the mother wavelet bandwidth, C DwF is the sub-wavelet center frequency, C MWF is the center frequency of the mother wavelet, ω c is the shift frequency.

[0046] The method for extracting harmonics from wavelength modulated spectra using continuous wavelet transform based on prior knowledge in the embodiment of the present application, on the basis of the traditional CWT method, uses the ideal harmonics obtained based on the WMS calculation model to construct the mother wavelet function. The mother wavelet function based on prior knowledge maximizes the correlation between the CWT filter convolution kernel and the effective signal, suppresses the noise of the same frequency as the harmonics to the greatest extent, and omits the process of optimizing the frequency scale when constructing the DWF, thereby greatly reducing the calculation time. In addition, when constructing the sub-wavelet, the shift scheme is used to achieve the decoupling of the frequency center and the frequency width, thereby solving the harmonic aliasing problem of the traditional CWT method. This embodiment uses a reasonable method to integrate the WMS physical model with the CWT algorithm, which improves the signal-to-noise ratio while reducing the optimization calculation time of harmonic extraction, thereby improving the convenience and efficiency of the method.

[0047] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0049] Figure 1 A schematic flow chart of a method for extracting harmonics from a continuous wavelet transform wavelength modulation spectrum based on prior knowledge provided in Example 1 of the present application;

[0050] Figure 2 Another schematic diagram of the process of the method for extracting harmonics from a continuous wavelet transform wavelength modulation spectrum based on prior knowledge according to an embodiment of the present application;

[0051] Figure 3 A schematic diagram of the structure of a harmonic extraction device of a continuous wavelet transform wavelength modulation spectrum based on prior knowledge provided in an embodiment of the present application. DETAILED DESCRIPTION

[0052] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0053] The following describes a method and device for extracting harmonics from a continuous wavelet transform wavelength modulation spectrum based on prior knowledge in an embodiment of the present application with reference to the accompanying drawings.

[0054] Figure 1 A flow chart of a method for harmonic extraction of continuous wavelet transform wavelength modulation spectroscopy based on prior knowledge provided in Example 1 of the present application is provided, which is used to realize harmonic signal extraction when performing gas measurement through TDLAS technology and wavelength modulation spectroscopy WMS technology.

[0055] like Figure 1 As shown, the continuous wavelet transform wavelength modulation spectrum harmonic extraction method based on prior knowledge includes the following steps:

[0056] Step 101, inputting the measurement parameters into the WMS physical model to obtain a theoretical transmittance signal, and obtaining theoretical harmonics through Fourier transform frequency selection;

[0057] Step 102, transforming the theoretical harmonics to satisfy the admission condition of the continuous wavelet transform CWT mother wavelet function, and obtaining the mother wavelet function based on prior knowledge;

[0058] Step 103, using a shift strategy, modulates the mother wavelet function based on prior knowledge to obtain a daughter wavelet function, and uses the daughter wavelet function as a CWT filter convolution kernel to process the transmitted light signal to obtain the target harmonic.

[0059] The method for extracting harmonics from wavelength modulated spectra using continuous wavelet transform based on prior knowledge in the embodiment of the present application, on the basis of the traditional CWT method, uses the ideal harmonics obtained based on the WMS calculation model to construct the mother wavelet function. The mother wavelet function based on prior knowledge maximizes the correlation between the CWT filter convolution kernel and the effective signal, suppresses the noise of the same frequency as the harmonics to the greatest extent, and omits the process of optimizing the frequency scale when constructing the DWF, thereby greatly reducing the calculation time. In addition, when constructing the sub-wavelet, the shift scheme is used to achieve the decoupling of the frequency center and the frequency width, thereby solving the harmonic aliasing problem of the traditional CWT method. This embodiment uses a reasonable method to integrate the WMS physical model with the CWT algorithm, which improves the signal-to-noise ratio while reducing the optimization calculation time of harmonic extraction, thereby improving the convenience and efficiency of the method.

[0060] Figure 2Another schematic diagram of the process of the harmonic extraction method of the continuous wavelet transform wavelength modulation spectrum based on prior knowledge in an embodiment of the present application.

[0061] like Figure 2 As shown in the figure, the method is mainly divided into: 1. Input experimental parameters (modulation coefficient m, scanning coefficient s, collision broadening v c 、Doppler broadening v d , modulation frequency F m and scanning frequency F s ) to the WMS physical model to obtain the theoretical transmittance signal, and then obtain the theoretical harmonics through Fourier transform frequency selection; 2. The theoretical harmonics are transformed to meet the permissible conditions of the CWT mother wavelet function to obtain the final mother wavelet function based on prior knowledge; 3. The shift strategy is used to construct the sub-wavelet function, and it is used as the convolution kernel to process the experimental signal to obtain the final experimental harmonics.

[0062] The principle of traditional CWT involves selecting a mother wavelet, constructing a daughter wavelet, and using it as a convolution kernel to extract the target harmonics, such as Figure 2 (a), its mathematical expression is as follows:

[0063] ψ a,b (t) = a -1 / 2 ψ(at-b)

[0064] CWT a (t) = f(t)*ψ a,0 (t)=∫f(t′)×ψ a,t (-t′)dt′

[0065] Where a and b are the frequency scale and time scale respectively. The frequency scale a corresponds to the stretching and compression of the wavelet, while the time scale b corresponds to the translation of the wavelet. a,b (t) and ψ(t) are the daughter wavelet and mother wavelet in the time domain, respectively, while CWT a (t) represents the continuous wavelet transform coefficient of f(t) at the frequency scale a.

[0066] Since the correlation between the mother wavelet function and the target harmonic significantly affects the extraction performance, using prior knowledge when building the model can maximize the harmonic extraction effect. Therefore, when building a mother wavelet based on prior knowledge, first simulate the harmonics through the physical model of WMS. After determining the measurement parameters of the model input (such as modulation and scanning coefficients, Gaussian broadening and collision broadening), the harmonics can be obtained by calculation:

[0067]

[0068] Among them, X 2 and Y 2 represents the vertical phase-locked decomposition result of 2f, Gopt is the photoelectric gain, I 1,M is the modulation amplitude of the laser intensity, is the average value of the laser output intensity, φ 1,M is the phase angle of wavelength modulation, H k is the frequency kf m The complex Fourier coefficient of the transmission intensity. Among the 2f components, $H_2$ is the main target component in WMS, and H 1 and J 3 is regarded as a distortion. Therefore, in PK-S-CWT, based on J 2 Constructing the mother wavelet function can enhance the target features and suppress the 1 and J 3 In order to construct the mother wavelet function, H 2 The admissibility conditions of the CWT mother wavelet function must be met:

[0069]

[0070] ∫ |t|＜T dt|ψ(t)| 2 ≥(1-ε)||ψ(t)|| 2

[0071] ∫ψ(t) 2 dt=1

[0072] ∫ψ(t 1 )ψ(t 2 )dt=δ(t 1 ,t 2 )

[0073] Then, when constructing the sub-wavelet function, the shift strategy is used instead of the traditional stretching and shrinking. This scheme can well achieve the decoupling of frequency center and frequency bandwidth:

[0074]

[0075] By using The modulator wavelet function can adjust the center frequency independently, so that the frequency scale a can be optimized according to the shape of the target harmonic, such as Figure 2 (b) As shown. The mother wavelet function is modulated by this method to obtain the final daughter wavelet function, and this daughter wavelet function is used as the convolution kernel to process the transmitted light signal and obtain harmonics, as shown in Figure 2 (c) as shown.

[0076] This embodiment significantly improves the signal-to-noise ratio of harmonics and the detection limit of the measurement system. Due to the strong correlation between the mother wavelet function and harmonics in the time domain and the consistency of amplitude and phase in the frequency domain, CWT can suppress the noise of the same frequency as the harmonics that is difficult to remove in traditional methods and greatly improve the signal-to-noise ratio of harmonics (increased by 78.7%), reducing the detection limit of the system.

[0077] This embodiment reduces the algorithm optimization time and simplifies the process of harmonic extraction. In the prior art solution, a lot of time is needed to optimize the filter parameters (cutoff frequency, filter order and other parameters), which seriously affects the convenience and measurement effect of WMS in actual measurement. This embodiment combines the prior knowledge of WMS and directly obtains the optimal mother wavelet function of CWT through a forward physical model, replacing the traditional iterative parameter optimization process (calculation time is reduced by 98.6%), greatly reducing the calculation time and simplifying the process of the method.

[0078] This embodiment significantly improves the robustness of the method to the measurement parameters (modulation coefficient, etc.). In the prior art solution, when optimizing the measurement parameters with the signal-to-noise ratio as the goal, a smaller filter width is used, which makes the measurement system extremely sensitive to the measurement parameters. This embodiment extracts harmonics in a more stable manner based on the mother wavelet function of prior knowledge, relying on the correlation in the time domain rather than the unstable frequency domain filtering method, thereby avoiding the conflict between the signal-to-noise ratio and the robustness of the modulation index, thereby ensuring good robustness while optimizing the signal-to-noise ratio.

[0079] In order to implement the above embodiment, the present application also proposes a continuous wavelet transform wavelength modulation spectrum harmonic extraction device based on prior knowledge, which is used to realize harmonic signal extraction when gas measurement is performed using TDLAS technology and wavelength modulation spectroscopy WMS technology.

[0080] Figure 3 A schematic diagram of the structure of a harmonic extraction device of a continuous wavelet transform wavelength modulation spectrum based on prior knowledge provided in an embodiment of the present application.

[0081] like Figure 3 As shown, the continuous wavelet transform wavelength modulation spectrum harmonic extraction device based on prior knowledge includes:

[0082] A priori knowledge module is used to input the measurement parameters into the WMS physical model to obtain the theoretical transmittance signal and obtain the theoretical harmonics through Fourier transform frequency selection;

[0083] Improved CWT module is used to transform theoretical harmonics to satisfy the admissible conditions of CWT mother wavelet function, obtain mother wavelet function based on prior knowledge, and use shift strategy to modulate mother wavelet function based on prior knowledge to obtain daughter wavelet function.

[0084] The harmonic extraction module is used to process the transmitted light signal using the sub-wavelet function as the CWT filter convolution kernel to obtain the target harmonic.

[0085] Optionally, in one embodiment of the present application, the measurement parameters include modulation coefficient, scanning coefficient, collision broadening, Doppler broadening, modulation frequency and scanning frequency.

[0086] Optionally, in one embodiment of the present application, the measurement parameters are input into the WMS physical model to obtain a theoretical transmittance signal, including:

[0087] The measured parameters are input into the WMS physical model, and the simulated harmonics are output, where the simulated harmonics are expressed as:

[0088]

[0089] Among them, X 2 and Y 2 represents the vertical phase-locked decomposition result of 2f, G opt is the photoelectric gain, I 1,M is the modulation amplitude of the laser intensity, is the average value of the laser output intensity, φ 1,M is the phase angle of wavelength modulation, H k is the frequency kf m The complex Fourier coefficient of the transmission intensity, H 1 , H 3 For distortion.

[0090] Optionally, in one embodiment of the present application, the theoretical harmonic H 2 The permissible conditions of the CWT mother wavelet function satisfied after the transformation are:

[0091]

[0092] ∫ |t|＜T dt|ψ(t)| 2 ≥(1-ε)||ψ(t)|| 2

[0093] ∫ψ(t) 2 dt=1

[0094] ∫ψ(t 1 )ψ(t 2 )dt=δ(t 1 ,t 2 )

[0095] ∫ψ(t 1 )ψ(t 2 )dt=δ(t 1 ,t 2 )

[0096] Among them, ω is the frequency, ε is an arbitrary small quantity, t is the time, ψ(ω) is the frequency domain expression of the wavelet function, ψ(t) is the time domain expression of the wavelet function, and δ(,) is the impulse function.

[0097] Optionally, in one embodiment of the present application, a shift strategy is used to modulate a mother wavelet function based on prior knowledge to obtain a daughter wavelet function, including:

[0098] By using Modulate the sub-wavelet functions and adjust the center frequency independently so that the frequency scale a is optimized according to the shape of the target harmonics;

[0099] The modulation process is expressed as:

[0100]

[0101] in, is the time domain expression of the daughter wavelet function, ψ(at-b) is the mother wavelet function, j is a unit imaginary number, W DWF is the sub-wavelet bandwidth, W MWF is the mother wavelet bandwidth, C DWF is the sub-wavelet center frequency, C MWF is the center frequency of the mother wavelet, ω c is the shift frequency.

[0102] It should be noted that the above explanation of the embodiment of the method for extracting harmonics from a continuous wavelet transform wavelength modulation spectrum based on prior knowledge is also applicable to the device for extracting harmonics from a continuous wavelet transform wavelength modulation spectrum based on prior knowledge of this embodiment, and will not be repeated here.

[0103] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0104] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0105] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0106] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute the instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0107] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0108] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0109] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0110] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for extracting harmonics from continuous wavelet transform wavelength modulation spectrum based on prior knowledge, characterized in that: The method is used to realize harmonic signal extraction when gas measurement is performed by using TDLAS technology and wavelength modulation spectroscopy WMS technology, and the method comprises: The measurement parameters are input into the WMS physical model to obtain the theoretical transmittance signal, and the theoretical harmonics are obtained through Fourier transform frequency selection; The theoretical harmonics are transformed to satisfy the admissible conditions of the CWT mother wavelet function, and the mother wavelet function based on prior knowledge is obtained; The shift strategy is used to modulate the mother wavelet function based on prior knowledge to obtain a daughter wavelet function, and the daughter wavelet function is used as a CWT filter convolution kernel to process the transmitted light signal to obtain the target harmonic.

2. The method according to claim 1, characterized in that The measurement parameters include modulation coefficient, scanning coefficient, collision broadening, Doppler broadening, modulation frequency and scanning frequency.

3. The method according to claim 1, characterized in that The step of inputting the measurement parameters into the WMS physical model to obtain a theoretical transmittance signal includes: The measured parameters are input into the WMS physical model, and the simulated harmonics are output, wherein the simulated harmonics are expressed as: Among them, X2 and Y2 represent the vertical phase-locked decomposition results of 2f, G opt is the photoelectric gain, I 1,M is the modulation amplitude of the laser intensity, is the average value of the laser output intensity, φ 1,M is the phase angle of wavelength modulation, H k is the frequency kf m The complex Fourier coefficients of the transmission intensity, H1 and H3 are distortions.

4. The method according to claim 3, characterized in that The permissible condition of the CWT mother wavelet function satisfied by transforming the theoretical harmonic H2 is: ∫ |t|＜T dt|ψ(t)| 2 ≥(1-ε)∥ψ(t)∥ 2 ∫ψ(t) 2 dt=1 ∫ψ(t1)ψ(t2)dt=δ(t1,t2) Among them, ω is the frequency, ε is an arbitrary small quantity, t is the time, ψ(ω) is the frequency domain expression of the wavelet function, ψ(t) is the time domain expression of the wavelet function, and δ(,) is the impulse function.

5. The method according to claim 1, characterized in that The shift strategy is used to modulate the mother wavelet function based on prior knowledge to obtain a daughter wavelet function, including: By using Modulate the sub-wavelet functions and adjust the center frequency independently so that the frequency scale a is optimized according to the shape of the target harmonics; Wherein, the modulation process is expressed as: in, is the time domain expression of the daughter wavelet function, ψ(at-b) is the mother wavelet function, j is a unit imaginary number, W DWF is the sub-wavelet bandwidth, W MWF is the mother wavelet bandwidth, C DWF is the sub-wavelet center frequency, C MWF is the center frequency of the mother wavelet, ω c is the shift frequency.

6. A harmonic extraction device for continuous wavelet transform wavelength modulation spectrum based on prior knowledge, characterized in that: The device is used to extract harmonic signals when measuring gas by using the TDLAS technology and the wavelength modulation spectroscopy WMS technology, and the device comprises: A priori knowledge module is used to input the measurement parameters into the WMS physical model to obtain the theoretical transmittance signal and obtain the theoretical harmonics through Fourier transform frequency selection; An improved CWT module is used to transform the theoretical harmonics so that they meet the admission conditions of the continuous wavelet transform CWT mother wavelet function, obtain the mother wavelet function based on prior knowledge, and use a shift strategy to modulate the mother wavelet function based on prior knowledge to obtain a daughter wavelet function; The harmonic extraction module is used to process the transmitted light signal using the sub-wavelet function as a CWT filter convolution kernel to obtain the target harmonic.

7. The device according to claim 6, characterized in that The measurement parameters include modulation coefficient, scanning coefficient, collision broadening, Doppler broadening, modulation frequency and scanning frequency.

8. The device according to claim 6, characterized in that The step of inputting the measurement parameters into the WMS physical model to obtain a theoretical transmittance signal includes: The measured parameters are input into the WMS physical model, and the simulated harmonics are output, wherein the simulated harmonics are expressed as: Among them, X2 and Y2 represent the vertical phase-locked decomposition results of 2f, G opt is the photoelectric gain, I 1,M is the modulation amplitude of the laser intensity, is the average value of the laser output intensity, φ 1,M is the phase angle of wavelength modulation, H k is the frequency kf m The complex Fourier coefficients of the transmission intensity, H1 and H3 are distortions.

9. The device according to claim 8, characterized in that The permissible condition of the CWT mother wavelet function satisfied by transforming the theoretical harmonic H2 is: ∫ |t|＜T dt|ψ(t)| 2 ≥(1-ε)||ψ(t)|| 2 ∫ψ(t) 2 dt=1 ∫ψ(t1)ψ(t2)dt=δ(t1,t2) Among them, ω is the frequency, ε is an arbitrary small quantity, t is the time, ψ(ω) is the frequency domain expression of the wavelet function, ψ(t) is the time domain expression of the wavelet function, and δ(,) is the impulse function.

10. The device according to claim 6, characterized in that The shift strategy is used to modulate the mother wavelet function based on prior knowledge to obtain a daughter wavelet function, including: By using Modulate the sub-wavelet functions and adjust the center frequency independently so that the frequency scale a is optimized according to the shape of the target harmonics; Wherein, the modulation process is expressed as: in, is the time domain expression of the daughter wavelet function, ψ(at-b) is the mother wavelet function, j is the unit imaginary number W DWF is the sub-wavelet bandwidth, W MWF is the mother wavelet bandwidth, C DWF is the sub-wavelet center frequency, C MWF is the center frequency of the mother wavelet, ω c is the shift frequency.

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