:<math>
\exp[-(\pi f_{\delta} \tau)^2] = \exp[-(\pi \Delta f \tau)^2] = \delta
\quad \Rightarrow \quad \tau = \frac{\sqrt{-\ln\delta}}{\pi f_{max}}</math>
<!--[[Image:FDTD64(1).png]]-->
\exp[ -[\pi(f_{\delta} - f_0)\tau] ^2 ] = \exp \left[ -\left(\pi \frac{\Delta f}{2} \tau\right)^2 \right] = \delta
\quad \Rightarrow \quad
\tau = \frac{2\sqrt{-\ln \delta}}{\pi \Delta f}</math>
<!--[[Image:FDTD65.png]]-->
\tilde{F}(f) = \int_{-\infty}^{\infty} f(t) e^{-j2\pi f t} \, dt
\quad \approx \quad
\Delta t \sum_{n=0}^N f(n\Delta t) e^{-j2 \pi n f \Delta t}</math>
<!--[[Image:FDTD68.png]]-->
:<math>
\mathbf{E^{inc}}(r,t) = (E_{\theta}^{inc} \hat{\theta} + E_{\phi}^{inc} \hat{\phi})
f \left[ (t-t_0) - \frac{\mathbf{\hat{k} \cdot r} - l_0}{c} \right]</math>
<!--[[Image:FDTD69.png]]-->