29-03-2012, 03:35 PM
Digital Filter Specifications
1-Digital_filters_(FIR).ppt (Size: 707 KB / Downloads: 156)
These filters are unealisable because (one of the following is sufficient)
their impulse responses infinitely long non-causal
Their amplitude responses cannot be equal to a constant over a band of frequencies
Another perspective that provides some understanding can be obtained by looking at the ideal amplitude squared.
Selection of Filter Type
The transfer function H(z) meeting the specifications must be a causal transfer function
For IIR real digital filter the transfer function is a real rational function of
Linear phase
For phase linearity the FIR transfer function must have zeros outside the unit circle