dfilt.df1 (Signal Processing Toolbox)

Construct a discrete-time, direct form I filter object

Syntax

```
Hd = dfilt.df1(b,a)
Hd = dfilt.df1
```

Description

Hd = dfilt.df1(b,a) returns a discrete-time, direct form I filter object, Hd, with numerator coefficients b and denominator coefficients a.

Hd = dfilt.df1 returns a default, discrete-time, direct form I filter object, Hd, with b=1 and a=1. This filter passes the input through to the output unchanged.

Note If a(1) is not equal to 1, the 1/a(1) block is included as shown below. If a(1) is equal to 1, the 1/a(1) block is replaced by a direct connection.

Examples

Specify a second-order direct form I structure for a dfilt object, Hd, with the following code:

b = [0.3 0.6 0.3];
a = [1 0 0.2];
Hd = dfilt.df1(b,a)
Hd =
     FilterStructure: 'Direct form I'
           Numerator: [0.3000 0.6000 0.3000]
         Denominator: [1 0 0.2000]

dfilt.cascade dfilt.df1sos