R&S®EVS-K4 FFT Technical Explanation

FFT - General Information

While the FSCAN mode is used to scan a signal in the RF range, the FFT (Fast Fourier Transformation) is used to scan in the baseband range. This is useful if you want to display the different components of a signal (see example) or analyse a signal supplied at the external baseband input.

Window Functions

The choice of the FFT window will determine frequency resolution, shape factor and sidelobe suppression.

Flat Top Window

  • Frequency resolution: Modest (equivalent resolution BW = 0.8 % of span)
  • Shape factor: Excellent
  • Sidelobe suppression: Excellent
  • Animated example

Hann Window

  • Frequency resolution: Good (equivalent resolution BW = 0.31 % of span)
  • Shape factor: Medium
  • Sidelobe suppression: Poor
  • Animated example

No Window

  • Frequency resolution: Optimum (equivalent resolution BW = 0.2 % of span)
  • Shape factor: Very poor
  • Sidelobe suppression: Very poor
  • Animated example
Back