PROPAGATION CONSTANT AND THE VELOCITY OF THE COHERENT WAVE IN A DENSESTRONGLY SCATTERING MEDIUM

Frequency- and time-domain experiments are conducted to study the effe ctive propagation constant of the coherent wave in a dense strongly sc attering medium, A wide-band microwave signal (10-40 GHz) is propagate d through randomly distributed glass spheres with a 5.73 mm average di ameter and separated into incoherent and coherent fields. The real and imaginary parts of the propagation constant are obtained from the coh erent field, The narrow size distribution of the particles enables us to study scattering from the Rayleigh region through the Mie resonance scattering region, The results of the experiments are compared to ind ependent scattering, effective-field approximation (Foldy's), and the higher order quasi-crystalline approximation (QCA) using Mie scatterin g coefficients and the Percus-Yevick approximation for the pair-distri bution function, The phase and group velocities of the coherent wave a re obtained from the effective propagation constant and compared with theory, In addition, the velocity of the coherent wave in random media is measured using the time-domain technique, It is shown that the vel ocity of the coherent wave in random media is neither phase nor group velocity.