Complex FFT
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Standard FFT function in SIGVIEW operates on real-valued sequences, i.e. real signal. If your signal is complex, i.e. contains complex samples, you can still calculate its FFT by using Complex-FFT function in Signal calculator . Good examples of such signals are complex signals used in for signal analysis in radio communication.

Before applying this function, you need to load both real and complex part of your signal as separate signal windows in SIGVIEW. Alternatively, you can perform 2-channel data acquisition where the first channel contains real values and the second one complex values. Afterwards, simply open Signal calculator window, choose real signal component, then press Complex FFT button, and then finally choose your imaginary signal component. The result should look like this:

graphic


Press OK button in Signal calculator dialog and a new window containing complex FFT will appear. As expected, its frequency axis will contain both negative and positive frequencies.

If your real and complex signals have different lengths, SIGVIEW will use only a part of the longer signal (starting from its first sample) which has the length of the smaller signal.
Complex FFT