MATLAB: How to plot x(t) = 0.9^k*cos(pi*k/5)*u(k) with simulink

plot simulink

I tried to plot x(t) = 0.9^k*cos(pi*k/5)*u(k) with simulink.
I used constant, sine wave, Pulse generator and product block in order to express 0.9, cos(pi/5), and u(t). But I couldn't figure out how to express 0.9^k.
Please help…

Best Answer

Something is wrong with that equation, can you see the error?
here's the MATLAB code, I leave the simulink for you to do, it's easy after knowing the basics.
k=1:100; %samples
u(k)=ones(1,numel(k)); %the input is a discrete step
x(k) = 0.9.^k.*cos(pi*k/5).*u(k);
plot(k,x(k))
hold on
plot(k,u(k),'r')
axis([0 numel(k) -2 2])
legend('x(k)=0.9^k*cos(pi*k/5)*u(k)','u(k)')
I couldn't wait so I just tested it on simulink, never done something similar before so I improvised, the results are similar to those of the script.
First thing you should do is change the configuration parameters.
Start time -> 1 Stop time -> 100 Solver Type -> Fixed step Sample time -> 1
Now the blocks
Clock -> Fcn -> Scope
In the Fcn put the expression -> 0.9^u*cos(pi*u/5)
Do the simulation
PS: Don't blame me if there's something wrong, try it and check if all is correct.
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