Aerosol Particle Beam Modulation for Resolution and Sensitivity
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Solution Overview
Problem
Existing methods for determining aerosol particle size distribution face a trade-off between resolution and sensitivity, as forming narrow pulses for high resolution reduces sensitivity and forming broad pulses for higher sensitivity reduces resolution.
Innovation Solution
The method involves modulating an aerosol particle beam with a controlled modulation function, guiding it through a drifting region, and calculating the correlation of the modulation function and signal to determine particle size distribution, allowing for multiple pulses while maintaining high resolution and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If narrow pulses of aerosol particle beam are formed to provide higher flight time resolution, then measurement precision is improved, but sensitivity is reduced due to reduced duty cycle
Solution Approach 1:
The patent applies periodic modulation of the aerosol particle beam using a pseudo-random binary sequence (PRBS) gate, creating a series of periodic pulses instead of continuous or single pulses. This periodic action allows multiple pulses to pass through the drift region simultaneously, maintaining high duty cycle while preserving flight time resolution through correlation processing of the modulated signal
Solution Approach 2:
The patent uses correlation processing between the known modulation function (PRBS sequence) and the detected signal to extract flight time information. This feedback mechanism allows the system to process modulated signals from multiple simultaneous pulses, recovering both high resolution and high sensitivity by comparing the received signal with the expected modulation pattern
2Quantity of substance
If broad pulses of aerosol particle beam are formed to provide enhanced sensitivity, then quantity of substance measured is improved, but flight time resolution is reduced
Solution Approach 1:
Instead of using single broad pulses, the system employs periodic modulation with PRBS sequences that create multiple narrow pulses within the modulation period. This maintains the benefits of periodic sampling for sensitivity while preserving the narrow pulse width needed for flight time resolution through the time-correlation processing of the modulated signal
Solution Approach 2:
The aerosol particle beam is pre-modulated with a known PRBS sequence before entering the drift region. This preliminary modulation encodes the timing information in a way that allows subsequent correlation processing to extract precise flight time data even when multiple pulses are present, effectively preparing the signal for high-resolution measurement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the determination of aerosol particle size distribution with a higher signal-to-noise ratio and improved measurement speed, achieving enhanced sensitivity and resolution simultaneously.
Implementation Method 1
guiding the modulated aerosol particle beam through a drifting region
Data Source
AI summary
The invention relates to a method and an apparatus (1) for determining an aerosol particle size distribution. The method includes the steps of modulating an aerosol particle beam (6) with an aerosol particle gate (2) which is controlled by a modulation function for generating a modulated aerosol particle beam, of guiding the modulated aerosol particle beam through a drifting region (3), of measuring a signal of the modulated aerosol particle beam after the modulated aerosol particle beam has passed the drifting region (3) and of calculating a correlation of the modulation function and the signal in order to determine the size distribution of the aerosol particles. The apparatus (1) includes an aerosol particle gate (2) which is controlled by a modulation function for generating from an aerosol particle beam (6) a modulated aerosol particle beam, a drifting region (3) through which the modulated aerosol particle beam is guidable, a detector (4) by which the signal of the modulated aerosol particle beam is measurable after the modulated aerosol particle 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 size distribution of the aerosol particles.