Analog Filter Design (DSP Blockset)

Design and implement an analog filter.

Library

Description

The Analog Filter Design block designs and implements a Butterworth, Chebyshev type I, Chebyshev type II, or elliptic filter in a highpass, lowpass, bandpass, or bandstop configuration.

The input must be a sample-based scalar signal.

The design and band configuration of the filter are selected from the Design method and Filter type pop-up menus in the dialog box. For each combination of design method and band configuration, an appropriate set of secondary parameters is displayed.

Filter Design
Description

Butterworth

The magnitude response of a Butterworth filter is maximally flat in the passband and monotonic overall.

Chebyshev type I

The magnitude response of a Chebyshev type I filter is equiripple in the passband and monotonic in the stopband.

Chebyshev type II
The magnitude response of a Chebyshev type II filter is monotonic in the passband and equiripple in the stopband.

Elliptic
The magnitude response of an elliptic filter is equiripple in both the passband and the stopband.

Filter Design	Description
Butterworth	The magnitude response of a Butterworth filter is maximally flat in the passband and monotonic overall.
Chebyshev type I	The magnitude response of a Chebyshev type I filter is equiripple in the passband and monotonic in the stopband.
Chebyshev type II	The magnitude response of a Chebyshev type II filter is monotonic in the passband and equiripple in the stopband.
Elliptic	The magnitude response of an elliptic filter is equiripple in both the passband and the stopband.

The table below lists the available parameters for each design/band combination. For lowpass and highpass band configurations, these parameters include the passband edge frequency _p, the stopband edge frequency _s, the passband ripple R_p, and the stopband attenuation R_s. For bandpass and bandstop configurations, the parameters include the lower and upper passband edge frequencies, _p1 and _p2, the lower and upper stopband edge frequencies, _s1 and _s2, the passband ripple R_p, and the stopband attenuation R_s. Frequency values are in rad/s, and ripple and attenuation values are in dB.

Lowpass
Highpass
Bandpass
Bandstop

Butterworth
Order, _p
Order, _p
Order, _p1, _p2
Order, _p1, _p2

Chebyshev Type I
Order, _p, R_p
Order, _p, R_p
Order, _p1, _p2, R_p
Order, _p1, _p2, R_p

Chebyshev Type II
Order, _s, R_s
Order, _s, R_s
Order, _s1, _s2, R_s
Order, _s1, _s2, R_s

Elliptic
Order, _p, R_p, R_s
Order, _p, R_p, R_s
Order, _p1, _p2, R_p, R_s
Order, _p1, _p2, R_p, R_s

	Lowpass	Highpass	Bandpass	Bandstop
Butterworth	Order, _p	Order, _p	Order, _p1, _p2	Order, _p1, _p2
Chebyshev Type I	Order, _p, R_p	Order, _p, R_p	Order, _p1, _p2, R_p	Order, _p1, _p2, R_p
Chebyshev Type II	Order, _s, R_s	Order, _s, R_s	Order, _s1, _s2, R_s	Order, _s1, _s2, R_s
Elliptic	Order, _p, R_p, R_s	Order, _p, R_p, R_s	Order, _p1, _p2, R_p, R_s	Order, _p1, _p2, R_p, R_s

The analog filters are designed using the Signal Processing Toolbox's filter design commands buttap, cheb1ap, cheb2ap, and ellipap, and are implemented in state-space form. Filters of order 8 or less are implemented in controller canonical form for improved efficiency.

Dialog Box

The parameters displayed in the dialog box vary for different design/band combinations. Only a portion of the parameters listed below are visible in the dialog box at any one time.

Design method: The filter design method: Butterworth, Chebyshev type I, Chebyshev type II, or Elliptic. Tunable.
Filter type: The type of filter to design: Lowpass, Highpass, Bandpass, or Bandstop. Tunable.
Filter order: The order of the filter, for lowpass and highpass configurations. For bandpass and bandstop configurations, the order of the final filter is twice this value.
Passband edge frequency: The passband edge frequency, in rad/s, for the highpass and lowpass configurations of the Butterworth, Chebyshev type I, and elliptic designs. Tunable.
Lower passband edge frequency: The lower passband frequency, in rad/s, for the bandpass and bandstop configurations of the Butterworth, Chebyshev type I, and elliptic designs. Tunable.
Upper passband edge frequency: The upper passband frequency, in rad/s, for the bandpass and bandstop configurations of the Butterworth, Chebyshev type I, or elliptic designs. Tunable.
Stopband edge frequency: The stopband edge frequency, in rad/s, for the highpass and lowpass band configurations of the Chebyshev type II design. Tunable.
Lower stopband edge frequency: The lower stopband edge frequency, in rad/s, for the bandpass and bandstop configurations of the Chebyshev type II design. Tunable.
Upper stopband edge frequency: The upper stopband edge frequency, in rad/s, for the bandpass and bandstop filter configurations of the Chebyshev type II design. Tunable.
Passband ripple in dB: The passband ripple, in dB, for the Chebyshev Type I and elliptic designs. Tunable.
Stopband attenuation in dB: The stopband attenuation, in dB, for the Chebyshev Type II and elliptic designs. Tunable.

References

Antoniou, A. Digital Filters: Analysis, Design, and Applications. 2nd ed. New York, NY: McGraw-Hill, 1993.

Supported Data Types

Double-precision floating point

To learn how to convert to the above data types in MATLAB and Simulink, see Supported Data Types and How to Convert to Them.

See Also

Digital Filter Design
DSP Blockset

buttap
Signal Processing Toolbox

cheb1ap
Signal Processing Toolbox

cheb2ap
Signal Processing Toolbox

ellipap
Signal Processing Toolbox

Digital Filter Design	DSP Blockset
`buttap`	Signal Processing Toolbox
`cheb1ap`	Signal Processing Toolbox
`cheb2ap`	Signal Processing Toolbox
`ellipap`	Signal Processing Toolbox

See the following sections for related information:

Filters
Analog IIR Filters
Filtering -- List of all DSP Blockset filtering blocks

Blocks -- Alphabetical List Analytic Signal