Flat Top Windows

The flat top window has the best amplitude accuracy of all the window functions. The increased amplitude accuracy (± 0.02 dB for signals exactly between integral cycles) is at the expense of frequency selectivity. The Flat Top window is most useful in accurately measuring the amplitude of single frequency components with little nearby spectral energy in the signal. The flat top window can be defined as

w(n) = a0 – a1*cos(2n/N) + a2*cos(4n/N) – a3*cos(6n/N) + a4*cos(8n/N),

where

a0 = 0.21557895,

a1 = 0.41663158,

a2 = 0.277263158,

a3 = 0.083578947, and

a4 = 0.006947368.

A flat top window is shown in the following illustration.