Filter transformation

1
Filter transformation High-pass Bandpass
Bandstop
wCHPws/2 -wCLP
Ws /2
Ws /2
WcLP
WcHP
Ws /2
Ws /2
WcLP
Wcu
Wcl
Ws /2
WcLP
Wcu
Wcl
Ws /2
2
IIR FILTER DESIGN
0. Determine the specifications for your filter
type, ripple, order,
Butterworth?
1. Determine the specifications for the
corresponding low pass filter ws, wcu, wLP
2. Determine the transfer function of the
normalised low pass filter H(s)

• Denormalise and calculate the analogue filter
  cut-off frequency
• prior to warping
  s -gt s/wa

4. Apply the bilinear transformation s
HLP(z)
5. Apply the low pass to ? Transformation (
zLP -gt f(?)) H(z)
6. Calculate the difference equation by taking
the inverse z-transform y(n)
7. Draw the physical realisation and justify your
choice almost done !