Understanding Digital Filters

Thread Starter

nanobyte

Joined May 26, 2004
120
In a book I read ("Digital Signaling Processing" by Steve White) there is a concept that I am having a hard time grasping. Why do digital filters repeat their gain characteristics past the folding frequency?
 

Papabravo

Joined Feb 24, 2006
13,931
In a book I read ("Digital Signaling Processing" by Steve White) there is a concept that I am having a hard time grasping. Why do digital filters repeat their gain characteristics past the folding frequency?
Because they can't tell the difference between the frequencies. The higher frequencies alias and are indistinguishable from the lower frequency.
 

Dave

Joined Nov 17, 2003
6,970
Without delving into the details of it, it is a consequence of the discrete Fourier transform. As Papabravo says, they are indistinguishable but very real frequency components and should be dealt with when processing such signals.

Dave
 
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