Matt Pitkin edited We_can_define_the_Fourier__.tex  over 8 years ago

Commit id: eba57acccdfccd616dd49ff2cef3c699a05a523e

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We can define the Fourier transform of our signal, which has complex amplitude at time $t_k$ of $y_k$ as  \begin{align}  H_k(f) \approx & y_k e^{i\phi_k-i\pi f \Delta t} \int_{-\Delta t/2}^{\Delta t/2} \exp{\left[2\pi i \left((f_k-f)t + \frac{t^2}{2}\dot{f}_k + \frac{t^3}{6}\ddot{f}_k \right) \right]} {\rm d}t  \nonumber \\ & + y_k^{*}e^{-i\phi_k-i\pi f \Delta t} \int_{-\Delta t/2}^{\Delta t/2} \exp{\left[-2\pi i \left((f_k+f)t - \frac{t^2}{2}\dot{f}_k - \frac{t^3}{6}\ddot{f}_k \right) \right]}. \right]} {\rm d} t.  \label{eq:fourier} \end{align}  The second term in this equation involving $(f+f_k)$ is negligible for our purposes, so only the first term is required.