Signal

$ x(t) = e^{jt} $

Energy

$ E_\infty = \int_{-\infty}^\infty |x(t)|^2dt $

$ = \int_{-\infty}^\infty |e^{jt}|^2dt $

$ = \int_{-\infty}^\infty |cos(t) + jsin(t)|^2dt $ (Euler's Formula)

$ = \int_{-\infty}^\infty {\sqrt{cos^2(t) + sin^2(t)}}^2dt $ (Magnitude of a Complex Number)

$ = \int_{-\infty}^\infty dt $

$ = t|_{-\infty}^\infty $

$ = \infty - (-\infty) $

$ = \infty $

Power

$ P_\infty = \lim_{T \to \infty} \frac{1}{2T} \int_{-T}^T |x(t)|^2dt $

$ = \lim_{T \to \infty} \frac{1}{2T} \int_{-T}^T |e^{jt}|^2dt $

$ = \lim_{T \to \infty} \frac{1}{2T} \int_{-T}^T |cos(t) + jsin(t)|^2dt $ (Euler's Formula)

$ = \lim_{T \to \infty} \frac{1}{2T} \int_{-T}^T {\sqrt{cos^2(t) + sin^2(t)}}^2dt $ (Magnitude of a Complex Number)

$ = \lim_{T \to \infty} \frac{1}{2T} \int_{-T}^T dt $

$ = \lim_{T \to \infty} \frac{1}{2T} t|_{-T}^T $

$ = \lim_{T \to \infty} \frac{1}{2T} [T - (-T)] $

$ = \lim_{T \to \infty} \frac{1}{2T} (2T) $

$ = \lim_{T \to \infty} 1 $

$ = 1 $

Alumni Liaison

has a message for current ECE438 students.

Sean Hu, ECE PhD 2009