It is the purpose of this paper to review some fundamental contributions related to the problem of understanding the fundamental properties of the Doppler signal produced by a single scattering particle and to present typical results obtained by a computational procedure developed at the Politecnico di Milano. The analysis is based on Mie scattering theory for spherical particles and provides useful and reliable information in any experimental situation, without restricting to asymptotic cases. Only by accounting for this information, mainly the signal visibility and the S/N, the optimum optical configuration and the proper signal processing system can be selected. It is shown that some general criteria can be inferred in order to optimize the LDA system design, including the possibility of selecting particle size and type by optical means, in the presence of a polydisperse distribution of scattering particles.