DSP Blockset

Analog Filter Design Block

The Analog Filter Design block designs and implements analog IIR filters with standard band configurations. All of the analog filter designs let you specify a filter order. The other available parameters depend on the filter type and band configuration, as shown in the following table.

Configuration	Butterworth	Chebyshev I	Chebyshev II	Elliptic
Lowpass	p	p, Rp	s, Rs	p, Rp, Rs
Highpass	p	p, Rp	s, Rs	p, Rp, Rs
Bandpass	p1, p2	p1, p2, Rp	s1, s2, Rs	p1, p2, Rp, Rs
Bandstop	p1, p2	p1, p2, Rp	s1, s2, Rs	p1, p2, Rp, Rs

The table parameters are

p	=	passband edge frequency
p1	=	lower passband edge frequency
p2	=	upper cutoff frequency
s	=	stopband edge frequency
s1	=	lower stopband edge frequency
s2	=	upper stopband edge frequency
Rp	=	passband ripple in decibels
Rs	=	stopband attenuation in decibels

For all of the analog filter designs, frequency parameters are in units of radians per second.

The Analog Filter Design block uses a state-space filter representation, and applies the filter using the State-Space block in the Simulink Continuous library. All of the design methods use Signal Processing Toolbox functions to design the filter:

• The Butterworth design uses the toolbox function butter.
• The Chebyshev type I design uses the toolbox function cheby1.
• The Chebyshev type II design uses the toolbox function cheby2.
• The elliptic design uses the toolbox function ellip.

The Analog Filter Design block is built on the filter design capabilities of the Signal Processing Toolbox. For more information on the filter design algorithms, see the Filter Designs section of the Signal Processing Toolbox documentation.

Note    The Analog Filter Design block does not work with the Simulink discrete solver, which is enabled when the discrete (no continuous states) option is selected in the Solver panel of the Simulation Parameters dialog box. Select one of the continuous solvers (such as ode4) instead.

Part 4 -- Looking at Filtering Results

Adaptive Filters