[Scilab-users] Bode of discret time transfer function.

Tim Wescott tim at wescottdesign.com
Sat Feb 25 22:57:31 CET 2017


Not sure what you're trying to achieve, but if you want a plot of the
linear amplitude response on a linear frequency line, use Horner:

H = syslin('d', (%z - 0.9) / (%z - 99));
th = %pi * (-1:0.01:1)';
clf; plot2d(th, abs(horner(H, exp(%i * th)))); xgrid(2)

On Sat, 2017-02-25 at 18:17 +0000, Pablo Fonovich wrote:
> Hi:
> This is the first time i work with discrete time transfers functions
> and Scilab.
> I want to use bode() for plotting the magnitud and phase response of
> the system, however, i don't understand how to set the frequencies to
> normalized values (-pi, pi).
> This is what i'm doing:
> 
> s=poly(0,'s')
> H=(s^(-2400))/(1-0.5*s^(-2400))
> S=syslin('d',H)
> bode(S)
> 
> i get a warning that frequencies beyond nyquist rate are ignored and
> the resulting plot is attached.
> 
> In the help, it says that bode parameter could include fmin and fmax
> in herz, but isn't a discrete system response limited to normalized
> frequencies? And to transform the normalized frecuency to herz the
> sample rate must be used, but i don't know how to pass it to the
> system or something.
> 
> Any hints would be appreciated.
> Thanks
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-- 

Tim Wescott
www.wescottdesign.com
Control & Communications systems, circuit & software design.
Phone: 503.631.7815
Cell:  503.349.8432






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