释义 |
Hanning FunctionAn Apodization Function, also called the Hann Function, frequently used to reduce Aliasing inFourier Transforms. The illustrations above show the Hanning function, its InstrumentFunction, and a blowup of the Instrument Function sidelobes. The Hanning function is given by
 | (1) |
The Instrument Function for Hanning apodization can also be written
 | (2) |
Its Full Width at Half Maximum is . It has Apparatus Function
The first integral is
 | (4) |
The second integral can be rewritten
Combining (4) and (5) gives
 | (6) |
To find the extrema, define and rewrite (6) as
 | (7) |
Then solve
 | (8) |
to find the extrema. The roots are and 10.7061, giving a peak Negative sidelobe of and a peakPositive sidelobe (in units of ) of 0.00843441. The peak in units of is 1, and the full-width at half maximum isgiven by setting (7) equal to 1/2 and solving for , yielding
 | (9) |
Therefore, with , the Full Width at Half Maximum is
 | (10) |
See also Apodization Function, Hamming Function |