Where to get it

Click here to download the package comprising the C-source for a very fast arbitrary N FFT routine as well as a benchmark program demonstrating the numerical capabilities and the performance of the routine. 




Mixfft contains the C source for a mixed-radix FFT routine. It performs a fast discrete Fourier transform (FFT) of a complex sequence, x, of an arbitrary length, n. The output, y, is also a complex sequence of length n.

The routine is accompanied by a demo program, fftbench.c, that demonstrates the numerical capabilities. It measures the execution time as well. If you wish to test the capabilities of another FFT routine, the fftbench.c is easy to modify.


For a really nice application using the FFT check out ScopeDSP.

The package contains four variants of the FFT. Download the zip file and read more about them in the mixfft.h file.


Real and imaginary part in separate arrays.


The inverse of fft


Trigonometric and factorization tables are setup prior to the fftCtxt. Context constructor and destructor functions are provided.


Same as above but with the input data provided in a single IQ array. Output is still in separate arrays.

Registered user

If you decide to use my routine either in a product or on a regular basis you (or your company) must pay a fee to become a registered user.

Please Contact me


Check out my YouTube channel to learn more about neat and useful math and algorithms.

Math Crumbs





If you have any questions please don’t hesitate to e-mail me. You can also take a look on some questions and answers I have collected from the past.