Signal Processing Blockset™

Analog Filter Design - Design and implement analog filters

Library

Filtering / Filter Designs

dsparch4

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, continuous-time, real-valued, 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.

The following table lists the available parameters for each design/band combination. For lowpass and highpass band configurations, these parameters include the passband edge frequency Ω_p, the stopband edge frequency Ω_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, Ω_p1 and Ω_p2, the lower and upper stopband edge frequencies, Ω_s1 and Ω_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, Ω_p	Order, Ω_p	Order, Ω_p1, Ω_p2	Order, Ω_p1, Ω_p2
`Chebyshev Type I`	Order, Ω_p, R_p	Order, Ω_p, R_p	Order, Ω_p1, Ω_p2, R_p	Order, Ω_p1, Ω_p2, R_p
`Chebyshev Type II`	Order, Ω_s, R_s	Order, Ω_s, R_s	Order, Ω_s1, Ω_s2, R_s	Order, Ω_s1, Ω_s2, R_s
`Elliptic`	Order, Ω_p, R_p, R_s	Order, Ω_p, R_p, R_s	Order, Ω_p1, Ω_p2, R_p, R_s	Order, Ω_p1, Ω_p2, R_p, R_s

The analog filters are designed using the filter design commands in Signal Processing Toolbox™ software's buttap, cheb1ap, cheb2ap, and ellipap functions, 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 some 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