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Can someone help evaluate the following integral? (I have tried doing it with Mathematica but I just get the integral back - I am assuming that it can't figure out how to solve it?)

\begin{equation} I=\int \frac{\csc ^2(\pi f) (\sin (2 \pi f))^{2a}}{-2 \cos (2 \pi a f)+\cos (2 \pi f-2 \pi a f)-2 \cos (2 \pi f)+3} \, df \end{equation}

$a(>>1)$ is just a constant. Some context:
The above integral is actually the result of a particular electrical circuit which implements the following $Z$ domain transfer function:

$\begin{equation} H(z)= \frac{\left(1-z^{-a}\right)^2}{\left(1-z^{-1}\right) \left(2-z^{-a}-z^{-1}\right)} \end{equation}$

where $z=e^{2\pi i f}$. In order to find the total power at the output, I need to evaluate the following integral:

$\begin{equation} \int_{f=0}^{f=f_s} |H(z)|^2 df \end{equation}$

The integral that you see in the first equation is actually the above function ($|H(z)|^2$) after simplification by Mathematica.

  • Hi! Welcome to MSE. Please share what you have tried. – Aditya Kumar Mar 08 '16 at 10:22
  • Hi Aditya, I haven't even tried solving this by hand (I did try with Mathematica to no avail). Could you help me get started on how I can solve this? – Saqib Shah Mar 08 '16 at 10:27
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    That indeed looks a bit messy. Do you have any reason to believe it does have a solution? It would help if you added some context to your question. – Daniel R Mar 08 '16 at 10:30
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    This actually comes out from an Analog to Digital Converters Noise transfer function - the circuit shapes the noise using the transfer function $\begin{equation} \bigg| \frac{\left(1-z^{-2}\right)^a}{\left(1-z^{-1}\right) \left(2-z^{-a}-z^{-1}\right)} \bigg|^2 \end{equation}$ $z$ is the complex exponential from the $Z$ transform.The above equation when simplified using Mathematica yields the trigonometric function above, which now needs to be integrated to find the total noise. I DO NOT know if the integral has a closed form. The only thing I have tried is to use Mathematica which doesnt work. – Saqib Shah Mar 08 '16 at 10:34
  • This question might be well-suited for dsp.stackexchange.com. – Daniel R Mar 08 '16 at 10:45
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    I think the DSP part is pretty much finished once the transfer function is evaluated. EE guys would be pretty much hopeless at solving integrals that mathematicians can't, or am I wrong there? – Saqib Shah Mar 08 '16 at 10:47

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