Real-time, non-invasive measurement of medical aerosol charge and size distribution: Signal processing strategy, system modelling and optimization

This paper describes and compares two particle excitation methods, square and sine wave, used in conjunction with novel application of Phase Doppler Anemometry (PDA) to obtain particle size and charge simultaneously in real time. Different signal processing strategies for particle velocity and size estimation are investigated, including Quadrature Demodulation (QD), spectral analysis and correlation technique. The system performance has been tested using Monte Carlo simulations obtained from the synthesized Doppler burst signals. Finally a mathematical model has been developed in order to estimate the percentage of particles captured in the measurement volume and successfully analyzed by the signal processing system leading to the optimization of the system parameters. It can be concluded that the signal processing system working in the square-wave excitation field and based on the spectral analysis performs better both in terms of the measurement range and the SNR requirement.