Step response of discrete-time filter System object


[stepResp,t] = stepz(sysobj)
[stepResp,t] = stepz(sysobj,n)
[stepResp,t] = stepz(sysobj,n,fs)
[stepResp,t] = stepz(sysobj,[],fs)
[stepResp,t] = stepz(sysobj,Name,Value)


[stepResp,t] = stepz(sysobj) computes the step response of the filter System object™, sysobj, and returns the response in column vector stepResp, and a vector of times (or sample intervals) in t, where t = [0 1 2 ...k-1]'. k is the number of filter coefficients.

[stepResp,t] = stepz(sysobj,n) computes the step response at floor(n) 1-second intervals. The time vector t equals (0:floor(n)-1)'.

[stepResp,t] = stepz(sysobj,n,fs) computes the step response at floor(n) 1/fs-second intervals. The time vector t equals (0:floor(n)-1)'/fs.

[stepResp,t] = stepz(sysobj,[],fs) computes the step response at k 1/fs-second intervals. k is the number of filter coefficients. The time vector t equals (0:k-1)'/fs.

[stepResp,t] = stepz(sysobj,Name,Value) returns a step response with additional options specified by one or more Name,Value pair arguments.

stepz(sysobj) uses fvtool to plot the step response of the filter System object sysobj.

For more input options, refer to stepz in Signal Processing Toolbox™ documentation.


stepz works for both real and complex filters. When you omit the output arguments, stepz plots only the real part of the step response.

Input Arguments

collapse all


Filter System object.

The following Filter System objects are supported by this analysis function:


Length of the step response vector.

Default: Number of filter coefficients


Sampling frequency.

Default: 1

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Specify the arithmetic used during analysis. When you specify 'double' or 'single', the function performs double- or single-precision analysis. When you specify 'fixed' , the arithmetic changes depending on the setting of the CoefficientDataType property and whether the System object is locked or unlocked.

 Details for Fixed-Point Arithmetic

When you do not specify the arithmetic for non-CIC structures, the function uses double-precision arithmetic if the filter System object is in an unlocked state. If the System object is locked, the function performs analysis based on the locked input data type. CIC structures only support fixed-point arithmetic.

Output Arguments


n-element step response vector. If n is not specified, the length of the step response vector equals the number of coefficients in the filter.


Time vector of length n, in seconds. t consists of n equally spaced points in the range (0:floor(n)-1)'/fs. If n is not specified, the function uses the number of coefficients of the filter.

See Also


Introduced in R2011a