C语言实现FFT算法的代码怎么写?
时间: 2023-05-21 18:07:37 浏览: 77
以下是一个实现FFT算法的C语言代码示例:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.141592654
typedef struct {
double real;
double imag;
} complex;
/* 计算X[k]的值 */
void fft(complex *X, int n)
{
int k; /* 迭代变量 */
int N = n/2; /* 每次迭代中模拟的DFT的点数 */
complex Wn; /* 旋转因子 */
complex *X1, *X2;
if (n == 1) {
/* 做一点没有意义的FFT */
return;
}
/* 分离x[n]的奇偶项 */
X1 = (complex *) malloc(N * sizeof(complex));
X2 = (complex *) malloc(N * sizeof(complex));
for (k = 0; k < N; k++) {
X1[k].real = X[2*k].real;
X1[k].imag = X[2*k].imag;
X2[k].real = X[2*k+1].real;
X2[k].imag = X[2*k+1].imag;
}
/* 递归计算下一级FFT */
fft(X1, N);
fft(X2, N);
/* 合并结果 */
for (k = 0; k < N; k++) {
Wn.real = cos(2 * PI * k / n);
Wn.imag = -sin(2 * PI * k / n);
X[k].real = X1[k].real + Wn.real * X2[k].real - Wn.imag * X2[k].imag;
X[k].imag = X1[k].imag + Wn.real * X2[k].imag + Wn.imag * X2[k].real;
X[k+N].real = X1[k].real - Wn.real * X2[k].real + Wn.imag * X2[k].imag;
X[k+N].imag = X1[k].imag - Wn.real * X2[k].imag - Wn.imag * X2[k].real;
}
free(X1);
free(X2);
}
/* FFT算法测试 */
int main(void)
{
int i, n;
complex *x, *X;
n = 8;
x = (complex *) malloc(n * sizeof(complex));
X = (complex *) malloc(n * sizeof(complex));
/* 在这里插入输入x[n]的代码 */
/* 调用FFT算法 */
fft(x, n);
/* 在这里插入输出X[k]的代码 */
free(x);
free(X);
return 0;
}