dfilt.df1t (Signal Processing Toolbox)

Discrete-time, direct-form I transposed filter

Syntax

Hd = dfilt.df1t(b,a)
Hd = dfilt.df1t

Description

Hd = dfilt.df1t(b,a) returns a discrete-time, direct-form I transposed filter, Hd, with numerator coefficients b and denominator coefficients a. The filter states for this object are stored in a filtstates object.

Hd = dfilt.df1t returns a default, discrete-time, direct-form I transposed filter, Hd, with b=1 and a=1. This filter passes the input through to the output unchanged.

Note The leading coefficient of the denominator a(1) cannot be 0.

To display the filter states, use this code to access the filtstates object.

Hs = Hd.states           % Where Hd is the dfilt.df1 object and
double (Hs)              % Hs is the filtstates object

The vector is

Examples

Create a direct-form I transposed discrete-time filter with coefficents from a fourth-order lowpass Butterworth design

[b,a] = butter(4,.5);  
Hd = dfilt.df1t(b,a)
Hd = 
     FilterStructure: 'Direct-Form I Transposed'
           Numerator: [0.0940 0.3759 0.5639 0.3759 0.0940]
         Denominator: [1 -3.6082e-016 0.4860 3.6545e-017 0.0177]
    PersistentMemory: false

dfilt.df1sos dfilt.df1tsos