National Instruments 320571-01 用户手册

Figure 1-1.  Choosing DSP2200 from the Functions Menu

The VIs in the Frequency Domain group are based upon the discrete implementation and optimization of the Fourier
Transform integral.  The Discrete Fourier Transform (DFT) of a complex sequence X containing n elements is
obtained using the following formula:

          

n-1

Y[i] = 

∑

  X[k] * exp (-j2

π

 ik / n),    for  i = 0, 1, …, n-1

          

k=0

where  Y[i]  is the ith element of the DFT of  X  and  j  =  

√

-1.

The DFT of X also results in a complex sequence Y of n elements.  Similarly, the Inverse Discrete Fourier
Transform (IDFT) of a complex sequence Y containing n elements is obtained using the following formula:

                    

n-1

X[i] = (1/n)  

∑

  Y[k] * exp (j2

π

 ik / n),    for  i = 0, 1, …, n-1

                   

k=0

where X[i] is the ith element of the IDFT of Y and j  =  

√

-1.