# Digital Signal Processing/Continuous-Time Fourier Transform

The **Continuous-Time Fourier Transform** (CTFT) is the version of the fourier transform that is most common, and is the only fourier transform so far discussed in EE wikibooks such as Signals and Systems, or Communication Systems. This transform is mentioned here as a stepping stone for further discussions of the **Discrete-Time Fourier Transform** (DTFT), and the **Discrete Fourier Transform** (DFT). The CTFT itself is not useful in digital signal processing applications, so it will not appear much in the rest of this book

## CTFT Definition[edit]

The CTFT is defined as such:

[CTFT]

## CTFT Use[edit]

## Frequency Domain[edit]

## Convolution Theorem[edit]

Multiplication in the time domain becomes convolution in the frequency domain. Convolution in the time domain becomes multiplication in the frequency domain. This is an example of the property of **duality**. The convolution theorem is a very important theorem, and every transform has a version of it, so it is a good idea to become familiar with it now (if you aren't previously familiar with it).

## Further reading[edit]

For more information about the Fourier Transform, see Signals and Systems.