<s>
In	O
numerical	B-General_Concept
analysis	I-General_Concept
,	O
the	O
uniform	B-Algorithm
theory	I-Algorithm
of	I-Algorithm
diffraction	I-Algorithm
(	O
UTD	O
)	O
is	O
a	O
high-frequency	B-Algorithm
method	O
for	O
solving	O
electromagnetic	O
scattering	O
problems	O
from	O
electrically	O
small	O
discontinuities	O
or	O
discontinuities	O
in	O
more	O
than	O
one	O
dimension	O
at	O
the	O
same	O
point	O
.	O
</s>
<s>
UTD	O
is	O
an	O
extension	O
of	O
Joseph	O
Keller	O
's	O
geometrical	B-Algorithm
theory	I-Algorithm
of	I-Algorithm
diffraction	I-Algorithm
(	O
GTD	O
)	O
.	O
</s>
<s>
The	O
uniform	B-Algorithm
theory	I-Algorithm
of	I-Algorithm
diffraction	I-Algorithm
approximates	O
near	O
field	O
electromagnetic	O
fields	O
as	O
quasi	O
optical	O
and	O
uses	O
knife-edge	O
diffraction	O
to	O
determine	O
diffraction	O
coefficients	O
for	O
each	O
diffracting	O
object-source	O
combination	O
.	O
</s>
