DSP Blockset

Creating a Lowpass Filter

The Digital Filter Design block, located in the DSP Blockset Filter Designs library, is useful for designing and implementing a digital FIR or IIR filter. In this example, you create a lowpass filter using the Digital Filter Design block. To implement a filter you already designed, see Digital Filter Block:

1. To create the lowpass filter in the model, open Simulink and create a new model file.
2. From the Filter Designs library, drag a Digital Filter Design block into your new model
3. Double-click the Digital Filter Design block.

1. The Filter Design and Analysis Tool (FDATool) GUI opens.

4. Set the block parameters of the GUI as shown in the following figure.
   
   
5. Click Design Filter at the bottom of the GUI to design the filter.

1. Your Digital Filter Design block now represents a filter with the parameters you specified. You can explore the other buttons, which provide other filter analysis tools such as pole-zero plots and impulse response plots. Click the Magnitude Response button  to view the original display.

6. In the Edit menu, select Convert Structure.

1. The Convert Structure dialog box opens.

7. Select Direct-Form FIR Transposed and click OK.

The Digital Filter Design block now represents a lowpass filter with a Direct-Form FIR Transposed structure. As the wpass and wstop settings indicate, the filter passes all frequencies up to 20% of the Nyquist frequency (half the sampling frequency), and stops frequencies greater than or equal to 50% of the Nyquist frequency.

To learn how to create a highpass filter using the Digital Filter Design block, see Creating a Highpass Filter.

Choosing Between Filter Design Blocks

Creating a Highpass Filter