How can I simulate a LTI system with complex data?

Question

Americo Cunha 2011-2-9

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回答： Rahim Gholami 2018-12-11

Hello,

I wrote a simple code to to simulate a LTI system:

% -----------------------------------------------------------

N = 200; t0 = 0.0;

t1 = 50.0;

T = t1-t0;

dt = T/(Nsteps-1);

time = (t0:dt:t1)';

f = zeros(N,1);

m = 1;

c = 1;

K = 5;

H = tf(1,[-m i*c k]);

h = impulse(H,time);

x = conv(f,h);

% -----------------------------------------------------------

But using the code above I receive the following message:

Cannot simulate the time response of LTI models with complex data.

Is there any way to compute the unit impulse response for a transfer function with complex entries?

I also appreciate other suggestions to solve this problem.

Thanks in advance.

Americo

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Answer 1

Gurudatha Pai 2011-6-18

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It looks like impulse() function does not take continuous time systems with complex coefficients; However, if I were to just solve this problem, you system has a unstable complex pole pair and no zeros. It would be a matter of using exponential functions with of the roots of denominator polynomial. Does that makes sense?

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Answer 2

Rajiv Singh 2011-6-19

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Simulation (time domain response calculation) of complex LTIs is not supported. You can cast is into a real system (as Gurudatha suggests), or convert your system into a model type used by System Identification Toolbox: H2 = idss(H); h2 = impulse(H2,time);