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Antenna
A: rx noise voltage A, signal voltage a
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Antenna
B: rx noise voltage B, signal voltage b
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After
correlation: (A+a).(B+b) = A.B + a.b + A.b + B.a
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Only a.b
may have a non-zero expectation value.
This is the
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desired,
correlated signal. The other terms
give purely random
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noise.
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In conventional interferometry, A>>a and B>>b,
so A.b and B.a
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are
negligible compared with A.B .
The
random noise on the
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image is dominated by A.B .
The
noise is statistically constant.
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With
FASR, usually a>>A
and b>>B, so A.B becomes negligible,
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and
the noise on the image
is dominated by A.b, B.a & a.b .
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Since
a and b are also highly variable with time,
this can
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give
noise in an image strange properties.
Some imaging
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algorithms
may not work as expected.
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