Work in progress for a formula sheet add things on :P?

  • Fourier series of a continuous-time signal x(t) periodic with period T
  • Fourier series coefficients of a continuous-time signal x(t) periodic with period T
$ CTFS $ $ x(t)=\sum_{n=-\infty}^\infty a_n e^{j \frac{2\pi}{T}nt}\;\;\;\;\;\;\;\;\;\;\;\;\;\;a_n=\frac{1}{T} \int_{0}^T x(t) e^{-j \frac{2\pi}{T}nt}dt $
$ CTFT $$ \ x(t) = \int_{-\infty}^{\infty} \chi(f)\ e^{j 2 \pi f t}\,df \;\;\;\;\;\;\;\;\;\;\;\;\;\ \chi(f) = \int_{-\infty}^{\infty} x(t)\ e^{- j 2 \pi f t}\,dt $
$ DFT $ $ \ X[k]=\sum_{k=0}^{N-1} x[n] e^{-j\frac{2 \pi k n}{N}}\;\;\;\;\;\;\; $ $ IDFT $ $ \ x[n]=\frac{1}{N} \sum_{n=0}^{N-1} X[k] e^{j\frac{2 \pi k n}{N}} $



$ rep_T [x(t)] = x(t)* \sum_{k=-\infty}^{\infty}\delta(t-kT) \;\;\;\;\;\;\;\;\;comb_T[x(t)] = x(t) . \sum_{k=-\infty}^{\infty}\delta(t-kT) $
$ rep_T [x(t)] \iff \frac{1}{T}comb_\frac{1}{T} [ \mathrm{X}(f)] \;\;\;\;\;\;\;\;\;\; comb_T [x(t)] \iff \frac{1}{T}rep_\frac{1}{T} [ \mathrm{X}(f)] $

$ \displaystyle\delta(\alpha f)= \frac{1}{\alpha}\delta(f)\;\;\;\;\;\;for\;\;\alpha>0 \;\;\;\;\;\;\;\;\;\;\;\;\;\;\;sinc(\theta)= \frac{sin(\pi\theta)}{\pi\theta} $

$ \displaystyle e^{j\pi}=-1 \;\;\;\;\;\;\; \cos(\theta) = \frac{(e^{j\theta}+e^{-j\theta})}{2}\;\;\;\;\;\;\;\;\;\;\;\; sin(\theta) = \frac{(e^{j\theta}-e^{-j\theta})}{2j} $

$ \mathcal{F}(\frac{rect( (t-\frac{T}{2})}{T})) \Rightarrow Tsinc(Tf)(e^{-j2 \pi f \frac{T}{2} }) $


Z-transform

$ Z-transform $ $ Z(x[n]) =\sum_{n=-\infty}^\infty x[n] z^{-n} $

Back to Exam 1 Discussion

Alumni Liaison

Prof. Math. Ohio State and Associate Dean
Outstanding Alumnus Purdue Math 2008

Jeff McNeal