CZT script 問題

- April 14, 2023 at 10:06 am
  
  Da cheng Mo
  Subscriber
  
  老師您好:
  想請問czt這個離散傅立葉的腳本，如果是傅立葉transform的話為什麼在sigma中的exp沒有負號？
  還有想請問他跟其他的傅立葉轉換比較的話是有做數學上的近似嗎？
  佛朗和斐:
  fresnal:
  
  謝謝您！
- April 14, 2023 at 7:44 pm
  
  Guilin Sun
  Ansys Employee
  
  谢谢指出。可能是漏掉负号了，我用czt 与Matlab比较，结果一样： https://www.mathworks.com/help/signal/ug/chirp-z-transform.html
  - April 16, 2023 at 8:00 am
    
    Da cheng Mo
    Subscriber
    
    老師您好:
    那在FDTD中有除了CZT之外，其他傅立葉轉換的方式嗎？
    - April 17, 2023 at 1:38 am
      
      Da cheng Mo
      Subscriber
      
      因為我用相同的近場影像，分別用CZT和fresnal propagation投影去遠場得出來的強度最大值不一樣。
      czt 投影結果:
      fresnal propagation公式和結果:
- April 17, 2023 at 4:05 pm
  
  Guilin Sun
  Ansys Employee
  
  幅值不一样正常，你看看CZT前面没有常数，而傅里叶变换前面有。此外，CZT里面也没有空间增量Delta。
  你可以用farfield3d，如果是几毫米的话，可以反算回来，参见 Adjusting the projection distance in far field projections

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