Upsample discrete-time models
sysl = upsample(sys,L)
sysl = upsample(sys,L) resamples the discrete-time dynamic system model sys at a sampling rate that is L-times faster than the sampling 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 sampling 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.
Create a transfer function with a sampling 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 Sampling 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 Sampling time: 0.16071
The sampling time of sys1 is 0.16071 seconds, which is 14 times faster than the 2.25 second sampling time of sys.