# SDR Theory

From Hamspirit wiki

## Useful links

- I/Q Data for Dummies A simple explaination of IQ signals.
- interactive complex FFT example
- The Scientist and Engineer's Guide to Digital Signal Processing
- http://www.earlevel.com/main/2010/12/11/a-closer-look-at-upsampling-filters/

## Polyphase discrete Fourier transform (Polyphase DFT)

AKA: "weighted overlap-add", "Window-presum FFT"

This technique is used to create a better spectrogram or panoramic display. It suffers less from the spectral-leakage that normal DFT has.