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Design Digital Filters in Simulink

Fixed-point digital filter design for embedded processors

In signal processing, a digital filter is a computational algorithm that converts a sequence of input numbers to a sequence of output numbers. The algorithm is designed such that the output signal meets frequency-domain or time-domain constraints (desirable frequency components are passed, undesirable components are rejected). In general terms, a discrete transfer function controller is a form of a digital filter. However, a digital controller can contain nonlinear functions such as lookup tables in addition to a discrete transfer function. This guide uses the term digital filter when referring to discrete transfer functions.

In the world of fixed-point numbers, where precision and range are limited, you must carefully select the data type, word size, and scaling for each realization element that results are accurately represented. To assist you with this selection, design rules for modeling dynamic systems with fixed-point math are provided in Targeting an Embedded Processor.


To design and implement a wide variety of floating-point and fixed-point filters suitable for use in signal processing applications and for deployment on DSP chips, use the DSP System Toolbox™.


  • Direct Form II

    Structure where coefficients of the transfer function appear directly as Gain blocks.

  • Series Cascade Form

    Transfer function that is written as a product of first-order and second-order transfer functions.

  • Parallel Form

    Transfer function that is expanded into partial fractions.

  • Canonical Forms

    Set of fundamental operations for the processor for a given digital filter.

  • Targeting an Embedded Processor

    Describes issues that arise when targeting a fixed-point design for use on an embedded processor.

  • fi Objects with DSP System Toolbox

    Describes how to pass fixed-point data back and forth between the MATLAB® workspace and Simulink® models using DSP System Toolbox blocks.

  • fi Objects with Simulink

    Describes the ways you can use Fixed-Point Designer™ fi objects with Simulink models.