Signal Processing Toolbox

Filter Structures

The available filter structures are:

• Direct-form, which includes direct-form I, direct-form II, direct-form I transposed, direct-form II transposed, and direc-form FIR
• Lattice, which includes lattice allpass, lattice MA min phase, lattice MA max phase, and lattice ARMA
• Discrete-time filter (dfilt object)

The structure that you choose determines the type of coefficients that you need to specify in the text fields to the right.

Direct-form

For direct-form I, direct-form II, direct-form I transposed, and direct-form II transposed, specify the filter by its transfer function representation

• The Numerator field specifies a variable name or value for the numerator coefficient vector b, which contains m+1 coefficients in descending powers of z.
• The Denominator field specifies a variable name or value for the denominator coefficient vector a, which contains n+1 coefficients in descending powers of z. For FIR filters, the Denominator is 1.

Filters in transfer function form can be produced by all of the Signal Processing Toolbox filter design functions (such as fir1, fir2, firpm, butter, yulewalk). See Transfer Function for more information.

Importing as second-order sections .   For all direct-form structures, except Direct-form FIR, you an import the filter in its second-order section representation:

The Gain field specifies a variable name or a value for the gain g, and the SOS Matrix field specifies a variable name or a value for the L-by-6 SOS matrix

whose rows contain the numerator and denominator coefficients b_ik and a_ik of the second-order sections of H(z).

Filters in second-order section form can be produced by functions such as tf2sos, zp2sos, ss2sos, and sosfilt. See Second-Order Sections (SOS) for more information.

Lattice

For lattice allpass, lattice minimum and maximum phase, and lattice ARMA filters, specify the filter by its lattice representation:

• For lattice allpass, the Lattice coeff field specifies the lattice (reflection) coefficients, k(1) to k(N), where N is the filter order.
• For lattice MA (minimum or maximum phase), the Lattice coeff field specifies the lattice (reflection) coefficients, k(1) to k(N), where N is the filter order.
• For lattice ARMA, the Lattice coeff field specifies the lattice (reflection) coefficients, k(1) to k(N), and the Ladder coeff field specifies the ladder coefficients, v(1) to v(N+1), where N is the filter order.

Filters in lattice form can be produced by tf2latc. See Lattice Structure for more information.

Discrete-time Filter (dfilt object)

For Discrete-time filter, specify the name of the dfilt object. See dfilt for more information.

Multirate Filter (mfilt object)

For Multirate filter, specify the name of the mfilt object. See mfilt in the Filter Design Toolbox for more information.

Importing a Filter Design

Exporting a Filter Design

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