Filter Design and Analysis

FIR, IIR, frequency transformations

You can design and analyze a variety of digital FIR and IIR filters using DSP System Toolbox™ functions and apps. Some of these filters include advanced filters such as Nyquist filters, halfband filters, advanced equiripple filters, and quasi-linear phase IIR filters.

The design techniques compute the filter coefficients based on the specifications. The analysis techniques help you validate the specifications of the designed filter. Analysis techniques include plotting the frequency response of the filter, finding the group delay of the filter, or determining if the filter is stable.

Filter design and analysis are complementary and iterative. After you design a filter, analysis tools help you determine if the filter meets the required specifications. The toolbox provides design and analysis apps such as filterBuilder and filterAnalyzer. To learn how to use filterBuilder, see Filter Builder Design Process.

You can also transform filters from one form to another form using functions such as firlp2hp, iirlp2bs, iirlp2bpc. To learn more about frequency transformations, see Digital Frequency Transformations.

Highlighted Topics

Featured Examples

Design Lowpass FIR Filters

Design lowpass FIR filters. You can extend many of the concepts presented here to other responses such as highpass, bandpass, and others.

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FIR Halfband Filter Design

Design FIR halfband filters. Halfband filters are widely used in multirate signal processing applications when you interpolate or decimate by a factor of two. In many cases, you can implement halfband filters efficiently in a polyphase form because nearly half of the halfband filter coefficients are equal to zero.

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Efficient Narrow Transition-Band FIR Filter Design

Design efficient FIR filters with very narrow transition-bands using multistage techniques. The techniques can be extended to the design of multirate filters. See Multistage Design Of Decimators/Interpolators for an example of that.

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Complex Bandpass Filter Design

Design complex bandpass filters. Complex bandpass filters are used in many applications from IF subsampling digital down converters to vestigial sideband modulation schemes for analog and digital television broadcast. One easy way to design a complex bandpass filter is to start with a lowpass prototype and apply a complex shift frequency transformation. This example reviews lowpass prototypes from single-stage single-rate FIR filters to multistage multirate FIR filters to IIR filters.