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I have shown that the minimum-phase helical factorization of the
Helmholtz equation can be applied recursively to extrapolate waves up
to 90, demonstrating the power of helical boundary
conditions to solve wave-equation PDE's.
For the constant coefficient case, however, pure Fourier domain
methods are still more efficient than the helical factorization, and
do not suffer from the technical problems related to
the factoring of functions with roots near the unit circle.
This means that the methodology in this chapter does not have wide
practical value, but rather serves as an conceptual introduction to
the following chapters.

** Next:** Helical factorization of paraxial
** Up:** Helical factorization of the
** Previous:** Reducing the filter length
Stanford Exploration Project

5/27/2001