 Considering the idea and theory of the "split-step" parabolic approximation, a discrete PE model using the Chebyshev spectral method (CSM) is derived, and the code is developed.
<meaning-changed>  Considering the idea and theory of the "split-step" parabolic approximation, a discrete PE model using the Chebyshev spectral method (CSM) is derived, and the code is developed.
 Considering the idea and theory of the wide-angle rational approximation, a discrete PE model using the Chebyshev spectral method (CSM) is derived, and the code is developed.