I have been given an input and output signal.

input: x(n)=(0.3^n)*u(n) + (5^n)*u(-n-1)

output: y(n)=(3^n)*u(-n-1) - ((2^(n+2))/(3^n))*u(n).


x=(0.3.^n).*(n>=0) + (5.^n). *(n<=-1) --> in Matlab

y=(3.^n). * (n<=-1) - 4. * ((2/3).^n).*(n>=0) --> in Matlab

I am supposed to find the tranfer function, it's poles and zeros and impulse response using matlab . I searched a lot but I couldn't find a way to aproach it in matlab.

I managed to find a transfer polynomial solving this on paper and came up with a=[-5 39.16 -74,63 19], as numerator coefficients and b=[0 -4.7 17.23 -9.4], as denominator coefficients. It turns out, whatsoever, that matlab can't make a valid computation of the poles and zeros as well as the impulse resonspe of the system since "the first denominator filter coefficient must be non-zero".

Any idea on how can I solve this exclusively using matlab or how can I eliminate the first 0 (zero) denominator coefficient?

thank you.


1 Answer 1


The Z-transform of the transfer function is $H(z) = Y(z)/X(z)$: the ratio of output to input Z-transforms.

Matlab provides a ztrans() method for computing Z-transforms symbolically (I didn't know this existed until now).

I'm assuming this is a homework problem, so I won't provide a complete solution.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.