c語言寫的fir低通濾波器

1、根據(jù) fir 濾波器的公式 y(n)= Eh(m)x(nm);(m: 0 (N-1).利用 MATLAB 產(chǎn)生濾波器系 數(shù)(h (n)并歸一化，下面為一個 LP 濾波算擊 void filter( void) uint16 i,j; fp32 sum; int16 x12030; fp32 h19= -0.0027, -0.0025, 0.0050, 0.0157, -0.0000, -0.0471, -0.0482, 0.0838, 0.2953, 0.4013, 0.2953, 0.0838, -0.0482, -0.0471, -0.0000,0.0157, 0.0050, -0.002

2、5, -0.0027; for(i=0;i2020;i+) x1i = data0i; for(i=0;i2020;i+) sum=0.0; for(j=0;j= j) sum+=hj*x1i-j; else ; data0i=(int16)sum; for(i=0;i2000;i+) data0i = data0i+20; 考慮到前 19個點為不完全累加和，故拋去前 19個點。(應(yīng)該是前后各 18個點都是 不完全累加和，都應(yīng)該去掉，對于數(shù)據(jù)分段進入濾波器的情況，應(yīng)該把前一段的后 面數(shù)據(jù)放到下一段的前面，這段時間我在解調(diào) FSK 時遇到了這個問題，通過濾波器 的數(shù)據(jù)的分段處理。) 設(shè)輸入數(shù)據(jù)x

3、N,輸出數(shù)據(jù)yN,濾波器系數(shù)hn 1.直接法(由y(m)=h(0)*x(m)+h(1)*x(m-1)+.+h(N-1)*x(m-n-1); void fir(short x, short h, short y) int i,j; long long sum; for (j = 0; j N; j+) sum = 0; for (i = 0; i 15; 乘法器使用次數(shù)：N*n 2逆推法： void fir(short x, short h, short y) int i,j; long sum; for (j = 0; j n; j+) for (i = 0; i 15; ) ) ) 乘法器使

4、用次數(shù)：N*n 3.倒序法：(輸入輸出可以是同一量) void fir(short x, short h口，short y) ( int i,j; long long sum; for (j = N; j 0; j-) ( sum = 0; for (i = n; i 0; i-) sum += xj-i * hi; yj = sum 15; ) )#include #include #define true 1 #define false 0 #define n 8 #define bufsize 100 /* the buffer size is 100 */ /* global decl

5、arations */ int in_bufferbufsize; /* processing data buffers */ int out_bufferbufsize; /* functions */ static int processing *input, int *output); static void dataio(void); static long round(long a); void main() int *input = &in_buffer0; int *output = &out_buffer0; puts(the 1st experiment st

6、artedn); /* loop forever */ while (true) /* * read input data using a probe-point connected to a host file. * write output data to a graph connected through a probe-point. */ / read the input signal. / if the input file is sine1.dat, the signal contains 300hz,400hz and 500hz. / if the input file is

7、sine2.dat, the signal contains 100hz,400hz and 500hz. / the sampling frequency is 1200hz. dataio(); /* remove the frequency compoment of 400hz and 500hz*/ processing(input, output); / write the output signal. / the output file is result.dat. dataio(); /* * = processing = * * function: apply a low-pa

8、ss fir filter to input signal and remove the frequency higher than 350hz. * * parameters: address of input and output buffers. * * return value: true. */ static int processing *input, int *output) int i,size = bufsize; short xx0,x,y; / short zn=0,0,0,0,0,0,0,0,0; short zn=0,0,0,0,0,0,0,0; /short w2*

9、n+1=22,356,155,990,466,220,777,216,777,26,466,9,155,0,22; /short w2*n+1=6,457,56,1024,224,418,523,382,784,99,784,43,523; / short w2*n+1=330*2,3299*2,1982*2,6867*2,4955*2,1594*2,6607*2,1065*2,4955*2,109*2,1982*2,17*2,330*2; /short w2*n+1=661,6598,3964,13733,9910,3187,13214,2131,9910,217,3964,34,661;

10、/ short w2*n+1=58,5628,526,8192,2105,5883,4913,3829,7369,1543,7369,504,4913,102,2105,14,526,1,58; /short w2*n+1=28,4432,280,8192,1259,4883,3356,3975,5873,1509,7048,644,5873,142,3356,30,1259,3,280,0,28; / short w2*n+1=26,651,182,1024,545,421,909,247,909,51,545,11,182,1,26; /short w2*n+1=831,20846,581

11、5,32768,17445,13486,29075,7888,29075,1647,17445,349,5815,21,831; /short w2*n+1=208,5211,1454,8192,4361,3371,7269,1972,7269,412,4361,87,1454,5,208; short w2*n+1=101,4356,810,8192,2835,3403,5670,2517,7088,605,5670,193,2835,21,810; / short w2*n+1=101,4356,810,8192,2835,3403,5670,2517,7088,605,5670,193,

12、2835,21,810,2,101; / short w2*n+1=50,3814,454,8192,1815,3504,4235*,3084,6353,831,6353,349,4235,50,1815,8,454,0,50; long y0,z0;/22222222222222 while (size-) xx0=*input+; x=xx0*6; z0=(long)x15; y0=0; for(i=0;i15); y0=round(y0); for(i=n-1;i0;i-) zi=zi-1; z0=round(z0); z0=(short)(z015); y=(short)(y015); *output+ =y; /* additional processing load */ return(true); /* * = dataio = * * function: read input signal and w