The multiple phase screens and Fourier-transform algorithm for numerical simulation of beam propagation through
atmospheric turbulence is important for imaging problems, lidar or laser radar. In this work Fast-Fourier-transform-based
model of phase screens are used to simulate the propagation of a radar beam. The refractive-index power spectrum used
for phase screen generation is the so-called modified atmospheric spectrum defined by L C Andrews. The standard
compensations used to correct the undersampling at low spatial frequencies are improved, and the limitations and
numerical requirements for a simulation of given accuracy are established. By using the improved algorithm, the
scintillation index of gaussian beams propagation through atmospheric turbulence is studied. Comparisons of simulations
with analytic results are presented. The on-axis theoretical scintillation index is compared with simulated results at
different ranges and good agreement is shown between numerical simulation and theoretical results.
Cat-eye effect of opto-electric system plays a important role in the active detection, which was studied by many
researchers based on the geometric methods. But in practical application of it on the war field, the laser beam must be
affected by the atmospheric turbulence, which make the conventional method invalid. The main subject of this paper is
to study the properties of the laser beam propagation through the atmospheric turbulence and cat-eye system. A
procedure is outlined to numerically simulate the propagation of beam through them. The effects of cat-eye system on
the wave field disturbed by the atmospheric turbulence are analyzed.