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![]() | Plane waves in three dimensions | ![]() |
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The filter can be lengthened in time but not in space.
The choice of exactly two columns is a choice
to have an analytic form that can exactly destroy
a single plane, but cannot destroy two.
Applied to two signals that are statistically independent,
the filter (2)
reduces to the well-known prediction-error filter
in the left column and zeros in the right column.
If the filter coefficients were extended
in both directions on
and to the right on
,
the two-dimensional spectrum of the input would be flattened.