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SUMMARY OF FILTER CHARACTERISTICS
EXTERNAL ANTI·ALlAS
I r<;j"
BW
's·BW
a. Original spectrum showing bandwidth of digital processing.
External anti-alias filter must pass below BW, stop beyond fs-BW
1
EXTERNAL ANTI·ALlAS
FILTER
,~L
INTERNAL
DIGITAL
FILTER
b. Spectrum using double rate sampling.
21
5
External filter passes BW, stops beyond 2f s -BW, internal digital filter performs
rest of anti-alias function.
Figure 5-18. Effects of Double Rate Input Sampling
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:~
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1.
8~.
Figure 5·19a. Cascade Structure for Complex Filter
(Directly Derived from Matched Z or Bilinear Transform)
5-18
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