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Digital Filter Analysis

Magnitude, phase, impulse, and step responses, phase and group delays, pole-zero analysis

Analyze frequency- and time-domain responses of filters. Visualize filter poles and zeros in the complex plane.


abs Absolute value (magnitude)
angle Phase angle
freqz Frequency response of digital filter
grpdelay Average filter delay (group delay)
phasedelay Phase delay of digital filter
phasez Phase response of digital filter
unwrap Correct phase angles to produce smoother phase plots
zerophase Zero-phase response of digital filter
zplane Zero-pole plot
impz Impulse response of digital filter
impzlength Impulse response length
stepz Step response of digital filter
filtord Filter order
filternorm 2-norm or infinity-norm of digital filter
firtype Type of linear phase FIR filter
isallpass Determine whether filter is allpass
isfir Determine if digital filter has finite impulse response
islinphase Determine whether filter has linear phase
ismaxphase Determine whether filter is maximum phase
isminphase Determine whether filter is minimum phase
isstable Determine whether filter is stable
fvtool Open Filter Visualization Tool
sptool Open interactive digital signal processing tool


Filter Designer Design filters starting with algorithm selection


Compensate for the Delay Introduced by an FIR Filter

Use indexing to counteract the time shifts introduced by filtering.

Compensate for the Delay Introduced by an IIR Filter

Remove delays and distortion introduced by filtering, when it is critical to keep phase information intact.

Take Derivatives of a Signal

Use a differentiator filter to differentiate a signal without amplifying the noise.

Speaker Crossover Filters

Devise a simple model of a digital three-way loudspeaker using Chebyshev Type I designs. Visualize the poles, zeros, and frequency responses of the filters.

Frequency Response

Compute and display frequency responses of IIR and FIR lowpass, highpass, and bandpass filters.

Magnitude and Phase

Extract magnitude and phase from a frequency response vector.


Measure the average time delay of a filter as a function of frequency.

Zero-Pole Analysis

Find and visualize poles and zeros of a linear system.

Impulse Response

Generate and display the impulse response of a simple filter.

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