我读到需要窗口来应用滤波器（低通、高通、带通或带阻），但不适用于 FFT。

1. 什么优点适用窗口或缺点不适用？

2. 选择尺码的标准是什么（我的长度W：汉窗的长度）？

3. 我在哪里可以找到具体的文献？

我的代码：

假设一个样本数组存储在

integer SIZE = 16384; //SomeValue
short[] sSamples = new short[SIZE];
sSamples = obtainSamples();  //Some method to fill my array

现在我需要获得我的 FFT。我为我的 FFT 任意选择了 4096，然后是 8 倍（或 8 fft）

FFTLength = 4096;
SIZE = 16384;
double Overlap = 0.5;
SIZE/(FFTLength*Overlap) = 8;

直接法：

complex cSamples = new complex[SIZE];
cSamples = short2Complex(sSamples);

现在我需要获取长度为 8 个样本数组的部分数组：SIZE/4

//getPartArray(from, until) maybe like System.ArrayCopy
complex[] cSamples00 = getPartArray(0,4095);
complex[] cSamples01 = getPartArray(4096,8191);
//similarly for all, from 00 until 07
complex[] cSamples01 = getPartArray(12287,16383);

最后，获得 FFT

//fft(complex[], length)
complex[] cFFT00 = fft(cSamples00,4096);
//similarly for all, from 00 until 07
complex[] cFFT07 = fft(cSamples00,4096);

窗口方法：

//int LengthW = ??  // (besides positive and odd)
double[] Wn = new double[LengthW];
//Suppose Han Window,can be Hamming, Kaiser, Blackman, etc
Wn = obtainHanWindow(LengthW);
double[] sWindowedSamples = applyingWindow(Wn,sSamples);

complex cSamples = new complex[SIZE];
cSamples = short2Complex(sWindowedSamples);

现在我需要获取长度为 8 个样本数组的部分数组：SIZE/4

//getPartArray(from, until) maybe like System.ArrayCopy
complex[] cSamples00 = getPartArray(0,4095);
complex[] cSamples01 = getPartArray(4096,8191);
//similarly for all, from 00 until 07
complex[] cSamples01 = getPartArray(12287,16383);

最后，获得 FFT

//fft(complex[], length)
complex[] cFFT00 = fft(cSamples00,4096);
//similarly for all, from 00 until 07
complex[] cFFT07 = fft(cSamples00,4096);

唯一的区别是计算一个窗口并将其应用于输入。

定义的类和方法

复杂类的定义如下：

class complex {
  public double real = 0.0;
  public double imag = 0.0;
} 

短2复杂：

short2Complex(short[] intSSample) {
  complex intCSample = new complex[intSSample.length];
  for (int i = 0; i < intSSample.length; i++) {
    complex tcomplex = new complex();
    tcomplex.real = intSSample[i];
    intCSample[i] = tcomplex;
  }
  return intCSample;
}

获取HanWindow：

double[] obtainHanWindow(int Size) {
  //Size must be Odd and Positive integer
  double[] dHan = new double[Size];
  int HalfSize = (int)Math.floor((double)Size/2);
  for (int i = 0; i < HalfSize; i++) {
    int j = 2*HalfSize - i;
    double Pi2DivSize = 2.0*Math.PI/Size;
    dHan[i] = 0.5+0.5*Math.cos(Pi2DivSize*(double)(i - HalfSize));
    dHan[j] = 0.5+0.5*Math.cos(Pi2DivSize*(double)(HalfSize - i));
  }
  dHan[HalfSize] = 1.0;
  return dHan;
}

应用窗口

applyingWindow(double[] dWn, double[] dSamples) {
  double dOutput = new double[dSamples.length]
  for (int i=0; i < dWn.length; i++) {
    dOutput[i] = 0;
    for (int j=0; j < dSamples.length; j++) {
      if(i-j>=0) {
        dOutput[i] += dSamples[j]*dWn[i-j];
      }
    }
  }
  return dOutput;
}