KR20120068181A - A signal process method for improving s/n of ion cyclotron resonance mass spectrometer - Google Patents

Abstract

PURPOSE: A method for processing an ion cyclotron resonance mass spectrograph is provided to reduce noise by performing a noise reduction operation process in regard to a noise component. CONSTITUTION: An analog signal obtained by a digitizer is transformed to a digital signal(S10). A DC voltage included in a signal component is eliminated(S20). Loss in regard to the signal component is reduced through a differentiation windowing signal processing process(S30). FFT calculation in regard to data of a time area is operated(S40). A noise component which is increased in the process that the FFT calculation is operated is eliminated(S50). A frequency area signal of the data in which noise is reduced is changed into a mass-to-electron ratio area(S60).

Description

A Signal Process Method for improving S / N of Ion Cyclotron Resonance Mass Spectrometer

The present invention relates to an ion cyclotron resonance mass spectrometer signal processing method, and more particularly, to a signal processing method of an ion cyclotron resonance mass spectrometer for signal-to-noise component improvement to reduce noise components using a noise reduction algorithm. .

A control device of a general ion cyclotron resonance mass spectrometer will be described in detail with reference to FIG. 1.

1 is an overall configuration diagram of a general ion cyclotron resonance mass spectrometer control device.

As shown in FIG. 1, a typical ion cyclotron resonance mass spectrometer includes a sample injection ionizer 1 for ionizing and releasing an injected sample, and a first ion for transmitting ions emitted from the sample injection ionizer 1. An ion selector (separation) unit 3 for selecting or separating and transmitting ions transmitted through the transmission unit 2 and the first ion transport unit 2 according to a specific purpose, and the ion selector (separation) unit 3 Ion bombardment part 4 which collides the ion selected or separated by impingement with the collision gas and emits it into smaller sizes, and a second ion transmitter 5 which transmits the ions divided by the ion bombardment part 4. In the ion trap 6 and the ion trap 6, which collects ions transmitted through the second ion transmitter 5 to an ion trap and detects an electrical signal representing a mass of ions meeting a specific purpose. Signal detection is carried out by the control program of the computer 10. An arbitrary waveform generator (AWG) 8 for generating an arbitrary waveform, an RF amplifier 7 for amplifying the generated arbitrary waveform, and an amplified waveform to the ion trap 6 to excite ions. .

The excited signal is passed through the digitizer (A / D) 10 through another electrode of the ion trap and amplified to a signal size suitable for detection through the preamplifier 11 shown in FIG. Signal processing is performed on the computer. In each step of control, a control signal is transmitted to the control device of each step through the control unit 12 by a control program operated by a computer.

The signal processor of the ion cyclotron resonance mass spectrometer according to the prior art is as shown in FIG.

In other words, Figure 2 is a flow diagram of the signal processing process of the ion cyclotron resonance mass spectrometer, the conventional ion cyclotron resonance mass spectrometer is a data acquisition process (S1) for obtaining data from the digitizer, windowing technique for improving the signal-to-noise ratio of the obtained data Windowing processing using S2, Fast Fourier Transformer (F3) processing time domain signal into frequency domain signal (S3), Mass domain display process converting frequency domain signal into m / z domain (S4) ) To perform a signal processing algorithm.

Here, although the noise may be reduced when performing the signal processing of the windowing process S2, which is a signal processing process, signal loss occurs.

Therefore, the ion cyclotron resonance mass spectrometer according to the prior art has a problem in that signal loss is inevitable because the windowing process selects only a limited area.

The present invention is to solve the above-mentioned problems, the signal loss generated during the windowing process of the ion cyclotron resonance mass spectrometer by processing the differential window to reduce the signal loss and increase the noise which is a disadvantage of the differential windowing noise reduction algorithm An object of the present invention is to provide an ion cyclotron resonance mass spectrometer signal processing method for improving signal-to-noise that is used to attenuate noise components.

In order to achieve the object of the present invention, the ion cyclotron resonance mass spectrometer signal processing process for improving the signal-to-noise is performed after the signal-to-noise ratio of the data obtained from the digitizer is improved, and the time-domain signal is processed to the frequency-domain signal by FFT (Fast Fourier Transformer). A signal processing method of an ion cyclotron resonance mass spectrometer for converting a frequency domain signal into a mass-to-charge ratio (m / z) region, the method comprising: a data acquisition process of converting an analog signal obtained through the digitizer into a digital signal (S10); A DC voltage processing step (S20) of removing the DC voltage included in the signal component obtained from the data acquisition step (S10); A differential window processing step (S30) of reducing the loss of signal components through differential windowing signal processing of the signal obtained through the DC voltage processing step (S20); An FFT process (S40) for performing a fast fourier transformer (FFT) operation on the data in the time domain obtained in the differential window processing process (S30); A noise reduction operation (S50) for removing an increased noise component in the operation calculated through the FFT process (S40); And a mass region display process S60 for converting the frequency domain signal of the noise reduced data from the noise reduction operation S50 to a mass-to-charge ratio (m / z) region.

The signal processing method of the ion cyclotron resonance mass spectrometer for improving the signal-to-noise according to the present invention performs differential order windowing to reduce the loss of signal components and a noise reduction operation for the increased noise components. It has a noise reduction effect.

1 is an overall configuration diagram of a general ion cyclotron resonance mass spectrometer control device,
Figure 2 is a flow diagram of the signal processing process of the ion cyclotron resonance mass spectrometer according to the prior art,
3 is a flowchart of a signal processing procedure of an ion cyclotron resonance mass spectrometer for signal-to-noise improvement according to an embodiment of the present invention;
4 is a comparison chart for finding an optimal point for signal-to-noise ratio calculation and resolving power through a differential window process and a noise reduction operation process according to an embodiment of the present invention.
5 is a diagram to help understand the differential windowing operation.

The signal processing method of the ion cyclotron resonance mass spectrometer for signal-to-noise improvement according to an embodiment of the present invention will be described in detail with reference to FIGS. 3 to 5 as follows.

An on-cyclotron resonance mass spectrometer control device for implementing the present invention has been described in the background art as shown in FIG. 1, and the present invention is denoted by the same reference numerals and the detailed description thereof is omitted.

That is, according to the present invention, the control signal generated by the signal processing algorithm in the computer 9 receiving the digital signal obtained through the digitizer 10 is transmitted to the control device of each stage through the control unit 12. .

As described above, the signal processing of the ion cyclotron resonance mass spectrometer for signal-to-noise improvement in the computer 9 will be described in detail with reference to FIG. 3.

3 is a flowchart illustrating a signal processing process of an ion cyclotron resonance mass spectrometer for improving signal-to-noise according to an embodiment of the present invention, and a data acquisition process of converting an analog signal obtained through the digitizer 10 into a digital signal (S10). And a DC voltage process (S20) for removing a DC voltage included in the signal component obtained from the data acquisition process (S10), and a signal obtained through the DC voltage process (S20) through differential windowing signal processing. Differential window processing to reduce the loss of signal components (S30), FFT processing (S40) to perform the FFT (Fast Fourier Transformer) operation on the data in the time domain obtained in the differential window processing (S30), and Noise reduction operation (S50) for removing the increased noise component in the process calculated through the FFT process (S40), and noise reduction from the noise reduction operation (S50) A frequency domain signal of the data comprises a mass area display process (S60) to be converted to a mass to charge ratio (m / z) domain.

When the signal processing method of the ion cyclotron resonance mass spectrometer for improving the signal-to-noise according to the embodiment of the present invention made as described above will be described in detail.

What is important in the differential window processing process 30 is how many different derivatives are performed.

When the signal f (t) in the time domain is expressed by a Fourier transform equation,

Equation 2 is an expression for n derivatives.

After all, performing n derivatives is equivalent to multiplying t times in the time domain.

Here, the problem is to multiply a few times to find a value that is optimized for signal components, noise and other signal characteristics (resolving power variables in mass spectrometers).

The noise reduction calculation process (S50) is to calculate the noise value through the following equation (3).

n _i : current noise component, n _i-1 : previous noise component,

n _mean : average of all data, M _i : current data value

n ₀ : First noise component calculation

First, an average value (n _mean ) for all data is calculated, and then a noise level for each data is calculated.

Find the first noise component (n ₀ ) for the first data. Follow the above formula or give an appropriate value. When determination of the value of α calculate the n _0, and determines the number equal to or smaller than zero is greater 1 M ₁ n value is greater than the _mean. Preferably it is determined to be 1, and vice versa to a number less than 0 and equal to or greater than -1, preferably -1. In this way, we find all n _i for each data.

That is, it depends on the signal condition, but if it is increased, it is +1 and if it is decreased, it is -1.However, if the precision is needed, it is bigger than 0 and equal to or less than 1 if it is increased by the algorithm. Or the same number.

When the noise values calculated in Equation 3 are subtracted through the following Equation 4, the calculated new data value S _i is obtained.

Where M _i is the current data value to be processed, S _i is the calculated current data value, and n _i is the current noise component calculation.

However, when the M _i value is 3 to 5 times larger than n _mean , it is preferably determined as 5. S _i applies to M _i .

That is, the noise subtraction in the same manner as in Equation 4 increases the noise level when the noise value included in the signal increases, and decreases the noise level when the noise value decreases to follow the increase and decrease of the noise component. There is this.

4 is a comparison chart of signal-to-noise ratio calculation and resolving power through differential window processing and noise reduction according to an embodiment of the present invention, which is included in a signal component through the DC voltage processing (S20). The signal-to-noise ratio (S / N) for the first to seventh order derivatives is calculated through the raw data from which the DC voltage is removed and the differential window processing process (S30), and the signal through the noise reduction operation process (S50). Noise reduction S / N can be calculated and the optimum differential order can be determined by comparing the resolving power that characterizes the mass signal.

Here, as shown in FIG. 4, it can be seen that the optimal signal improvement is obtained when the first derivative is performed. In other words, the optimal differential calculation point becomes the first derivative calculation point.

5A and 5B are explanatory diagrams for reducing signal loss due to differential windowing. When differential windowing is performed, starting at y = 1 when the starting point of the multiplication function as in FIG. 5B is x = 0, the original signal is saved. Comes out. However, when x = 0, as shown in FIG. 5a, even when starting from the origin of y = 0, there is a sufficient signal loss, but the same result is obtained.

The present invention is not limited to the above-described embodiments, and any person having ordinary skill in the art to which the present invention pertains can make various changes without departing from the gist of the present invention as claimed in the following claims. It will be said that there is a technical spirit of the present invention.

9: computer 10: digitizer
12: control unit

Claims (4)

After the signal-to-noise ratio is improved by the computer 9 receiving the data obtained from the digitizer 10, the time-domain signal is processed into a frequency domain signal by FFT (Fast Fourier Transformer), and the frequency-domain signal is mass-to-charge ratio (m / In the signal processing method of the ion cyclotron resonance mass spectrometer to convert to z) region,
A data acquisition process of converting an analog signal obtained through the digitizer 10 into a digital signal (S10);
DC voltage processing (S20) for removing the DC voltage included in the signal component obtained from the data acquisition process (S10) by the computer (10);
Differential windowing process to reduce the loss of the signal component of the signal obtained from the DC voltage processes (S20) through differential signal windowing process (S30);
An FFT process (S40) for performing a fast fourier transformer (FFT) operation on the data in the time domain obtained in the differential window processing process (S30);
A noise reduction operation (S50) for removing an increased noise component in the operation calculated through the FFT process (S40); And
And a mass domain display process (S60) for converting the frequency domain signal of the noise reduced data from the noise reduction operation process (S50) into a mass to charge ratio (m / z) region. Ion cyclotron resonance mass spectrometer signal processing method for The method of claim 1,
The differential window processing process (S30) and the noise reduction operation process (S50) calculate the new signal component by increasing or decreasing the noise value according to the signal component to improve the signal-to-noise ratio and the optimal derivative for the nth-order differential operation. Ion cyclotron resonance mass spectrometer signal processing method for improving the signal-to-noise, characterized in that to remove the noise components by calculating the operating point.
The method of claim 1,
The differential window processing process (S30) is an ion cyclotron resonance mass spectrometer signal processing method for improving the signal-to-noise, characterized in that performing the differential n times as shown in the following equation (1).
[Equation 1]

here,

Is the Fourier transform of the signal f (t) in the time domain.
The method of claim 1,
The noise reduction operation S50 may include calculating a _mean value n of all original signal data;
Calculating each noise value (n _i ) for the entire original signal data by the following equation (2);
&Quot; (2) "

Where, n _i is the current noise value, n _i-1 is the noise value of the immediately preceding, M _i is the data value for the current processing, n ₀ is the initial noise value, determined for the α value when calculating a n ₀ If the M ₁ value is greater than n _{mean, the number} is greater than 0 and equal to or less than 1, and the calculated noise values are subjected to the arithmetic operation according to the increase and decrease of the noise component according to the following equation 3 for each original signal data value. Ion cyclotron resonance mass spectrometer signal processing method for improving the signal-to-noise, characterized in that consisting of.
[Equation 3]

Where M _i is the current data value, S _i is the calculated current data value, n _i is the current noise value, and where M _i is 3 to 5 times larger than n _mean , S _i Applies M _i .

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