  We report the development of a new ray-tracing simulation tool having the
potential of the full characterization of a radio link through the accurate
study of the propagation path of the signal from the transmitting to the
receiving antennas across a perturbed atmosphere. The ray-tracing equations are
solved, with controlled accuracy, in three dimensions (3D) and the propagation
characteristics are obtained using various refractive index models. The
launching of the rays, the atmospheric medium and its disturbances are
characterized in 3D. The novelty in the approach stems from the use of special
numerical techniques dealing with so called stiff differential equations
without which no solution of the ray-tracing equations is possible. Starting
with a given launching angle, the solution consists of the ray trajectory, the
propagation time information at each point of the path, the beam spreading, the
transmitted (resp. received) power taking account of the radiation pattern and
orientation of the antennas and finally, the polarization state of the beam.
Some previously known results are presented for comparative purposes and new
results are presented as well as some of the capabilities of the software.
