Fourier formats for mixed radix disk format


IFORM
IMAGE/VOLUME ODD NX EVEN NX
2D -11 -12
3D -21 -22

Fourier files have NX changed depending on NX of the corresponding real file. For odd NX of a real file, the Fourier file will have record length NNNN=NX+1, for even NX of a real file, the Fourier file will have record length NNNN=NX+2. Thus, the record length of a Fourier file, both 2D and 3D is even.

The Fourier coefficients are written in in such a way that element (KX=0,KY=0,KZ=0) is in location (1,1,1).

First record contains Fourier coefficients:

    Location in file:          KX KY KZ
    1,1,1                 Re(  0  0  0)
    2,1,1                 Im(  0  0  0)
    3,1,1                 Re(  1  0  0)
    4,1,1                 Im(  1  0  0)
    .
    .
    NNNN-1,1,1            Re(NNNN/2  0  0)
    NNNN,1,1              Im(NNNN/2  0  0)

Record LY, LZ contains Fourier coefficients:

     Location in file:          KX   KY   KZ
      1,LY,LZ               Re(  0  LY-1 LZ-1)
      2,LY,LZ               Im(  0  LY-1 LZ-1)
      3,LY,LZ               Re(  1  LY-1 LZ-1)
      4,LY,LZ               Im(  1  LY-1 LZ-1)
      .
      .
      NNNN-1,LY,LZ          Re(NNNN/2  LY-1 L-1Z)
      NNNN,LY,LZ            Im(NNNN/2  LY-1 LZ-1)

Important: if KY>NY/2+1 the corresponding frequency becomes LY=KY-1-NY, if KZ>NZ/2+1 the corresponding frequency becomes LZ=KZ-1-NZ.

08/28/96 PP


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