DSP

C语言直接DFT和FFTW两种方式实现离散傅里叶变换

2019-07-13 20:31发布

站内文章 / DSP
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/* * dft.c * * Created on: 2018年5月16日 * Author: ChiWang */ #include #include #include "fftw3.h" #define N 16 //采样个数 #define PI 3.1415926535 typedef struct //complex数据类型，用于实现傅里叶运算 { float r; float i; }complex; complex dft_out[N]; //complex out data float dft_in[N]; //sample in data float amp[N]; //real_amp=amp*2/N void DFT_Cal(void) { int i = 0; int n = 0; complex part[N]; for(i=0; i f=50Hz,w=2*Pi/T -> w=2*pi*f -> 220sin(2*pi*f*t) dft_in[i] = 220*sin(2*PI*50*i*0.02/N);//一个周期采样N个点，那么一个点的时间就是T/N=0.02/N printf("%lf ",dft_in[i]); } /* fftw related init */ float *fft_in_buffer=NULL; fftwf_complex *fft_out_buffer = NULL; fftwf_plan fft_plan; size_t FFT_len = N; fft_in_buffer = (float *)fftwf_malloc(sizeof(float) * FFT_len); fft_out_buffer = (fftwf_complex *)fftwf_malloc(sizeof(fftwf_complex) * FFT_len); #define FFTW 1 #if FFTW fft_plan = fftwf_plan_dft_r2c_1d(FFT_len, dft_in, fft_out_buffer, FFTW_ESTIMATE); fftwf_execute(fft_plan); #else DFT_Cal();//进行DFT计算 #endif printf(" "); for(i=0; i1，使能FFTW，运行输出（#define FFTW 1，并下载libfftw3f-3.dll，然后编译时连接该库）：0.000000 84.190353 155.563492 203.253494 220.000000 203.253494 155.563492 84.190353 0.000000 -84.190353 -155.563492 -203.253494 -220.000000 -203.253494 -155.563492 -84.190353 
(freq=0.000000,amp=0.000000)
(freq=50.000000,amp=220.000000)
(freq=100.000000,amp=0.000000)
(freq=150.000000,amp=0.000002)
(freq=200.000000,amp=0.000000)
(freq=250.000000,amp=0.000002)
(freq=300.000000,amp=0.000000)
(freq=350.000000,amp=0.000006)
(freq=400.000000,amp=0.000000)
(freq=450.000000,amp=0.000000)
(freq=500.000000,amp=0.000000)
(freq=550.000000,amp=0.000000)
(freq=600.000000,amp=0.000000)
(freq=650.000000,amp=0.000000)
(freq=700.000000,amp=0.000000)2，直接DFT计算运行输出（#define FFTW 0）：0.000000 84.190353 155.563492 203.253494 220.000000 203.253494 155.563492 84.190353 0.000000 -84.190353 -155.563492 -203.253494 -220.000000 -203.253494 -155.563492 -84.190353 


(freq=0.000000,amp=0.000002)
(freq=50.000000,amp=220.000000)
(freq=100.000000,amp=0.000002)
(freq=150.000000,amp=0.000001)
(freq=200.000000,amp=0.000000)
(freq=250.000000,amp=0.000001)
(freq=300.000000,amp=0.000000)
(freq=350.000000,amp=0.000004)
(freq=400.000000,amp=0.000000)
(freq=450.000000,amp=0.000004)
(freq=500.000000,amp=0.000000)
(freq=550.000000,amp=0.000001)
(freq=600.000000,amp=0.000000)
(freq=650.000000,amp=0.000001)
(freq=700.000000,amp=0.000002)
(freq=750.000000,amp=220.000000)

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