Ion Mobility Spectrometer Modulation for Signal Noise
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Solution Overview
Problem
Existing ion mobility spectrometers face challenges in achieving a high signal-to-noise ratio while maintaining measurement speed, as the correlation calculation introduces features that can lead to misinterpretations in ion mobility spectra, limiting the dynamic range and requiring the discarding of small peaks as potential false peaks.
Innovation Solution
The method employs a modulation function with a two-valued autocorrelation and additional steps to calculate a blurred signal and its difference, followed by correlation with the modulation function, which improves resolution and reduces noise, using techniques such as convolution with symmetric functions and probability distributions to sharpen the correlation and suppress noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ion beam is modulated with a continuous modulation function and correlation calculation is performed, then measurement speed is improved, but the signal-to-noise ratio deteriorates due to introduction of artificial features
Solution Approach 1:
The patent changes the parameter of the modulation function from continuous to binary (two-valued), which fundamentally alters the autocorrelation properties. This parameter change eliminates the artificial features introduced by continuous modulation while preserving the ability to perform correlation calculation for fast measurement.
Solution Approach 2:
Instead of using continuous modulation functions and accepting the artificial features they produce, the patent inverts the approach by using binary modulation functions that inherently produce clean two-valued autocorrelation, thereby eliminating the problem rather than working around it.
2Reliability
If small peaks are discarded as false peaks to avoid misinterpretation, then reliability is improved, but the dynamic range deteriorates
Solution Approach 1:
The patent converts the previously harmful artificial features into a benefit by using binary modulation functions whose autocorrelation properties naturally produce clean, interpretable spectra without false peaks. This allows all peaks including small ones to be reliably interpreted, expanding dynamic range while maintaining accuracy.
3Adaptability or versatility
If the modulation function is varied over a large frequency range, then measurement versatility is improved, but device complexity increases
Solution Approach 1:
The patent changes the modulation function from continuous varying frequency to discrete binary sequences, simplifying the control mechanism while maintaining versatility through the use of different binary code sequences (e.g., Barker codes) that can be selectively applied.
Data Source
Figure 1a~1b
Figure 2~3
Figure 4~5
AI summary
The invention relates to a method and an apparatus (1) for determining a mobility of ions. The method includes the steps of modulating an ion beam (6) with an ion gate (2) which is controlled by a modulation function for generating a modulated ion beam, of guiding the modulated ion beam through a drifting region (3), of measuring a signal of the modulated ion beam after the modulated ion beam has passed the drifting region (3) and of calculating a correlation of the modulation function and the signal in order to determine the mobility of the ions. The apparatus (1) includes the ion gate (2), the drifting region (3) through which the modulated ion beam is guidable, a detector (4) by which the signal of the modulated ion beam is measurable after the modulated ion beam has passed the drifting region (3) and a calculation unit (5) by which the correlation of the modulation function and the signal is calculable in order to determine the mobility of the ions. An autocorrelation of the modulation function is a two-valued function.