제13주
Chapter 10 : Design of Digital Filters
10.1 General Considerations
In the filter design process
we determine the coefficients of a causal FIR or IIR filter that closely approximates the desired frequency response spec.
FIR: linear-phase characteistics.
IIR: lower sidelobes in the stopband, fewer parameters, less memory, lower computational complexity.
Frequency transformations
LP prototype filter -> BPF, BSF, HPF.
10.1.1 Causality and Its Implications
10.1.1 Causality and Its Implications
What are the necessary & sufficient conditions that a frequency response characteristic H(w) must satisfy for causality?
Conversely, if |H(w)| is square integrable and if the integral (8.1.3) is finite, then H(w) is causal.
The magnitude function |H(w)| can be zero at some frequencies, but it cannot be zero over any finite band of frequencies, since the
integral then becomes infinite.
Therefore, ideal filter is non-causal.
10.1.1 Causality and Its Implications
Causality on the real and imaginary components of H(w)
j
