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upsample

Upsample discrete-time models

Syntax

sysl = upsample(sys,L)

Description

sysl = upsample(sys,L) resamples the discrete-time dynamic system model sys at a sampling rate that is L-times faster than the sample time of sys (Ts0). L must be a positive integer. When sys is a TF model, H(z), upsample returns sysl as H(zL) with the sample time Ts0 / L.

The responses of models sys and sysl have the following similarities:

  • The time responses of sys and sysl match at multiples of Ts0.

  • The frequency responses of sys and sysl match up to the Nyquist frequency π / Ts0.

    Note:   sysl has L times as many states as sys.

Examples

Create a transfer function with a sample time that is 14 times faster than that of the following transfer function:

sys = tf(0.75,[1 10 2],2.25)

Transfer function:
     0.75
--------------
z^2 + 10 z + 2

Sample time: 2.25
To create the upsampled transfer function sys1, type the following commands:
L=14;
sys1 = upsample(sys,L)
These commands return the result:
Transfer function:
       0.75
------------------
z^28 + 10 z^14 + 2

Sample time: 0.16071
The sample time of sys1 is 0.16071 seconds, which is 14 times faster than the 2.25 second sample time of sys.

See Also

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Introduced in R2008b

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