COHERENT SCATTERING BY MULTIPLE PARTICLES IN-PHASE DOPPLER INTERFEROMETRY

A theoretical model has been developed for studying the response of th e phase Doppler interferometer when multiple particles are simultaneou sly present within the measurement probe volume. The developed model i ncorporates the geometrical optics theory for describing the coherent interaction between the scattered light signals of multiple particles, each having different size, velocity, trajectory, and arrival time. T he resulting Doppler signal is processed by a theoretical signal proce ssor which can simulate the performance characteristics of different s ignal processing schemes that are widely used in phase Doppler interfe rometry, namely, zero-crossing counter, covariance, autocorrelation, a nd DFT processors. The application of the developed model for studying the coherent scattering by two particles has been specifically addres sed in this paper. It has been shown that a DFT processor can be used to simultaneously measure the size and velocity of the two particles i n most instances. However, for more than two particles, the signal pro cessing scheme becomes more complex because of a quadratic increase in the beat frequency components.