Fast Fourier transform

Brief Description

File: \examples\Processing\Advanced\FastFourierTransform\mE5-MA-VCL\fft.va

File: \examples\Processing\Advanced\FastFourierTransform\mE5-VD8-CL\fft.va

Default Platform: mE5-MA-VCL or mE5-VD8-CL

Short Description

Shows the usage of operator FFT. The applet generates a sine pattern and performs the FFT. The results show the frequency part. Use the VisualApplets simulation.

The provided example will demonstrate the use of the FFT. In the example, a simple sine wave with period 256 and magnitude ± 16384 is generated.

Sinewave

Figure 216. Sinewave


The resulting real and imaginary part are squared and added. So the output is the squared absolute value.

The result shows the expected peak at x = 32 i.e. a period of 8192 / 32 = 256. At position 32 the real part value is -43 and imaginary part is -67108738. When we compare the values with a Matlab FFT calculation we see real = 8,7e-10 and imag = 6710900. So we can see that the result is very good. There exists a small inaccuracy in the calculation only.

FFT Result

Figure 217. FFT Result


The implementation is very simple. A sine wave input. H-Box DynamicReduceResolutionFFTOut is used to shift results and reduce their resolution. This is not required for the given sine wave.

FFT Result

Figure 218. FFT Result