请教一下关于FIR滤波器的程序问题

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reporter发表于 2013-9-18 14:40 | 只看该作者

请教一下关于FIR滤波器的程序问题

include, 滤波器, 信号源, 程序, 网上

我参照网上盛传的FIR滤波器程序，通过调整参数修改了模拟信号和模拟噪声的频率，生成了一个350Hz sin信号含50Hz cos噪声的信号源。通过以下程序进行处理。抽头系数为FDAT计算得出。FDAT设计时，采用blackman窗函数型设计的25阶带通滤波，通频带为100～1000Hz。
结果发现，50Hz低频信号滤除不掉，但修改噪声为4KHz时，可完全滤除。
请高手帮忙指点一下为什么会这样。谢谢。#include&lt;math.h&gt;#define FIRNUMBER 25#define SIGNAL1F 1000#define SIGNAL2F 4500#define SAMPLEF&nbsp;&nbsp;10000#define PI 3.1415926float InputWave();float FIR();//float fHn[FIRNUMBER]={ 0.0,0.0,0.001,-0.002,-0.002,0.01,-0.009,//&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;-0.018,0.049,-0.02,0.11,0.28,0.64,0.28,//&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;-0.11,-0.02,0.049,-0.018,-0.009,0.01,//&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp;&nbsp;-0.002,-0.002,0.001,0.0,0.0//&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;};float fHn[FIRNUMBER]={0.0,0.0,-0.001,-0.003,-0.009,-0.017,-0.022,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; -0.012,0.021,0.079,0.147,0.204,0.226,0.204,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; 0.147,0.079,0.021,-0.012,-0.022,-0.017,-0.009,&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; -0.003,-0.001,0.0,0.0&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp; };float fXn[FIRNUMBER]={ 0.0 };float fInput,fOutput;float fSignal1,fSignal2;float fStepSignal1,fStepSignal2;float f2PI;int i;float fIn[256],fOut[256];int nIn,nOut;main(){&nbsp; &nbsp; &nbsp; &nbsp; nIn=0; nOut=0;&nbsp; &nbsp; &nbsp; &nbsp; f2PI=2*PI;&nbsp; &nbsp; &nbsp; &nbsp; fSignal1=0.0;&nbsp; &nbsp; &nbsp; &nbsp; fSignal2=PI*0.1;&nbsp; &nbsp; &nbsp; &nbsp; fStepSignal1=2*PI/30;//&nbsp; &nbsp; &nbsp; &nbsp; fStepSignal2=2*PI*1.4;&nbsp; &nbsp; &nbsp; &nbsp; fStepSignal2=2*PI/200;&nbsp;&nbsp;/*1.4;*/&nbsp; &nbsp; &nbsp; &nbsp; while ( 1 )&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fInput=InputWave();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fIn[nIn]=fInput;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; nIn++; nIn%=256;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fOutput=FIR();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fOut[nOut]=fOutput;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; nOut++;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; /* 请在此句上设置软件断点 */&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if ( nOut&gt;=256 )&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; nOut=0;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }}float InputWave(){&nbsp; &nbsp; &nbsp; &nbsp; for ( i=FIRNUMBER-1;i&gt;0;i-- )&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fXn=fXn[i-1];&nbsp; &nbsp; &nbsp; &nbsp; fXn[0]=sin(fSignal1)+cos(fSignal2)/6.0;&nbsp; &nbsp; &nbsp; &nbsp; fSignal1+=fStepSignal1; &nbsp; &nbsp; &nbsp; &nbsp; if ( fSignal1&gt;=f2PI )&nbsp; &nbsp; &nbsp; &nbsp; fSignal1-=f2PI;&nbsp; &nbsp; &nbsp; &nbsp; fSignal2+=fStepSignal2;&nbsp; &nbsp; &nbsp; &nbsp; if ( fSignal2&gt;=f2PI )&nbsp; &nbsp; &nbsp; &nbsp; fSignal2-=f2PI;&nbsp; &nbsp; &nbsp; &nbsp; return(fXn[0]);}float FIR(){&nbsp; &nbsp; &nbsp; &nbsp; float fSum;&nbsp; &nbsp; &nbsp; &nbsp; fSum=0;&nbsp; &nbsp; &nbsp; &nbsp; for ( i=0;i&lt;FIRNUMBER;i++ )&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; fSum+=(fXn*fHn);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; return(fSum);}

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