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Picket fence effect or Scalloping

Started by rajgerman April 7, 2006
Hey 
 
Could anyone explain to me what the picket fence effect or scalloping 
is and how you would see such effects when doing fourier analysis and 
using windowing? 
 
I would appreciate any help. 
 
Thanks 
 
Raj
>Hey > >Could anyone explain to me what the picket fence effect or scalloping >is and how you would see such effects when doing fourier analysis and >using windowing? > >I would appreciate any help. > >Thanks > >Raj >
Picket fencing or scalloping effect is the fall off in frequency between two FFT bins. Scalloping Loss is the apparent attenuation of the measured value for a frequency component that falls exactly half way between FFT bins. Scalloping loss may be mathematically defined as the ratio of the power gain for a signal frequency component located half way between FFT bins, to the Coherent Power Gain for a signal frequency component located exactly on the FFT bin. Scalloping loss is one of the figure of merits to determine the quality of the FFT windowing function. It can be calculated by taking the ratio of the value of the window function's kernel one half a frequency sample off centre, to its value at the centre. - Krishna