Table of Fourier transform properties

This table is adapted and reworked from Dr Chris Jobling's resources, see this page. Other links: Properties of the Fourier Transform (Wikpedia) or Wikibooks: Engineering Tables/Fourier Transform Properties and Fourier Transfom—WolframMathworld for more complete references..

Name $x(n)$ $X(f)$ Remarks
1 Linearity $a_1x_1(n)+a_2f_2(t)+\cdots+a_kf_k(n)$ $a_1X_1(f)+a_2X_2( f)+\cdots+a_kX_k(f)$ Fourier transform is a linear operator.
2 Duality $$x(-f)$$ $$X(n)$$
3. Time and frequency scaling $$x(\alpha n)$$ $$\frac{1}{|\alpha|}S\left(\frac{ f}{\alpha}\right)$$ time compression is frequency expansion and vice versa
4. Time shifting $$x(n-n_0)$$ $$e^{-j2\pi f n_0}X(f)$$ A time shift corresponds to a phase shift in frequency domain
5. Frequency shifting $$e^{j2\pi f_0 n}x(n)$$ $$X(f-f_0)$$ Multiplying a signal by a complex exponential results in a frequency shift.
7. Frequency differentiation $$(-jn)^k x(n)$$ $$\frac{d^k}{d f^k}X(f)$$
8. Time integration $$\sum_{m=-\infty}^{n}f(m)$$ $$\frac{X(f)}{j2\pi f}+\pi X(0)\delta(f)$$
9. Conjugation $$s^*(n)$$ $$S^*(- f)$$
10. Time convolution $$x_1(n)*x_2(n)$$ $$X_1(f) X_2(f)$$
11. Frequency convolution $$x_1(n)x_2(n)$$ $$\frac{1}{2\pi} X_1(f)*X_2(f)$$ Application to amplitude modulation.
12. Sum of $x(n)$ $$\sum_{n=-\infty}^{\infty} x(n) $$ $X(0)$ Average value of a signal
13. Area under $X(f)$ $$f(0) $$ $$\frac{1}{2\pi}\int_{-\infty}^{\infty} X(f)\,df$$
15. Parseval's theorem $$\sum_{-\infty}^{\infty}|x(n)|^2$$ $$\frac{1}{2\pi}\int_{-\infty}^{\infty}|X(f)|^2\,df.$$