DSP Blockset

Choosing Between Filter Design Blocks

The Digital Filter Design block and Filter Realization Wizard block both let you design and implement digital filters. This topic explains the similarities and differences between the Digital Filter Design block and the Filter Realization Wizard. In addition, this topic covers how to choose the block that is best suited for your needs.

Similarities

The Digital Filter Design Block and Filter Realization Wizard are similar in the following ways:

• Filter design and analysis options -- Both blocks provide the Filter Design and Analysis Tool (FDATool) GUI for filter design and analysis.
• Output values -- In double precision, both blocks' outputs numerically match the outputs of the filter function in the Filter Design Toolbox and the filter function in the Signal Processing Toolbox.

Differences

The Digital Filter Design Block and Filter Realization Wizard handle the following things differently:

• Data type support -- Both blocks support single- and double-precision floating-point computation, but the Filter Realization Wizard additionally supports fixed-point computation.
• Filter implementation method
• The Digital Filter Design block implements very efficient filters that are optimized for both speed and memory use in simulation and in C code generation. For more information on code generation, see Code Generation Support.
• The Filter Realization Wizard implements filters using Sum, Gain, and Unit Delay blocks from either DSP Blockset or Fixed-Point Blockset.
• Supported filter structures -- Both blocks support many of the same basic filter structures, but the Filter Realization Wizard supports more structures than the Digital Filter Design block. See the Filter Realization Wizard and Digital Filter Design block reference pages for a list of all the structures they support.
• Multichannel filtering -- The Digital Filter Design block can filter multichannel signals. Filters implemented by the Filter Realization Wizard can only filter single-channel signals.

When to Use Each Block

The following are specific situations where only the Digital Filter Design block or the Filter Realization Wizard is appropriate.

• Digital Filter Design
• Use to simulate single- and double-precision floating-point filters.
• Use to filter multichannel signals.
• Use to generate highly optimized ANSI/ISO C code that implements floating-point filters for embedded systems. For more information on code generation, see Code Generation Support.
• Filter Realization Wizard
• Use to simulate numerical behavior of fixed-point filters in a DSP chip, FPGA, or ASIC.
• Use to simulate single- and double-precision floating-point filters with structures that the Digital Filter Design does not support.
• Use to visualize the filter structure (the block builds the filter from Sum, Gain, and Delay blocks).

See Filter Realization Wizard for information about this block.

Overview of the Digital Filter Design Block

Creating a Lowpass Filter