And through the comparisons of results, we analyzed the effects of sampling plane to far field, demonstrated the applicability of PWS theory to high and low directivity antennas , so that we can further researchthe error analysis and correction.

With a two dimensional problem as an example, the effect of scattering from wall of anechoic chamber on planar near field measurements with ultra low sidelobe antennas is studied by means of computer simulation based on theory of plane wave spectrum expansion and approximation in geometrical optics.

For spatial discretization,the compact finite difference schemes on non-uniform meshes in x and y direction are adopted with Fourier spectral expansion for numerical approximation in z direction,the spanwise direction.

By constructing a quasi birth-and-death process and applying the spectral expansion method the algorithm of stable indexes are given,especially the explicit expression of stationary distribution when c=2.