Contents

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

Ωp

Ωp, Rp

Ωs, Rs

Ωp, Rp, Rs

Highpass

Ωp

Ωp, Rp

Ωs, Rs

Ωp, Rp, Rs

Bandpass

Ωp1, Ωp2

Ωp1, Ωp2, Rp

Ωs1, Ωs2, Rs

Ωp1, Ωp2, Rp, Rs

Bandstop

Ωp1, Ωp2

Ωp1, Ωp2, Rp

Ωs1, Ωs2, Rs

Ωp1, Ωp2, Rp, Rs

The table parameters are

  • Ωp — passband edge frequency

  • Ωp1 — lower passband edge frequency

  • Ωp2 — upper cutoff frequency

  • Ωs — stopband edge frequency

  • Ωs1 — lower stopband edge frequency

  • Ωs2 — 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 Signal Processing Toolbox software.

    Note:   The Analog Filter Design block does not work with the Simulink discrete solver, which is enabled when the Solver list is set to Discrete (no continuous states) in the Solver pane of the Model Configuration Parameters dialog box. Select one of the continuous solvers (such as ode4) instead.

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