201203110317林逸磊_实验十一报告.docx

实验十一 FIR算法实验目的1、掌握用窗函数法设计FIR数字滤波器的原理和方法。2、熟悉线性相位FIR数字滤波器特性。3、了解各种窗函数对滤波器特性的影响。实验原理根据要求设计低通FIR滤波器。设计指标等效模拟滤波器指标：通带截止频率：10kHz阻带截止频率：16kHz阻带最小衰减：70dB采样频率：50kHz转换成数字滤波器指标：通带截止频率：0.4rad阻带截止频率：0.64rad阻带最小衰减：50dB设计计算过渡带宽：截止频率：理想低通滤波器脉冲响应：其中M为滤波器阶数。根据要求阻带衰减大小，选择Hamming窗。选择M=28，则窗函数长度N=29。窗函数为：滤波器脉冲响应为：根据上面计算，各式计算出。得到的滤波器系数为：{ -0.0014,0.001534,0.00228,-0.004,-0.0047372,0.01,0.00839,-0.0222,-0.012545,0.04478,0-0-0.019,0.314,0.52,0.314,-0.019,-000.04478,-0.012545,-0.0222,0.00839,0.01,-0.0047372,-0.004,0.00228,0.001534,-0.0014 }实验程序分析//#include C5509.h//#include ICETEK-VC5509-EDU.h#include math.h#define FIRNUMBER 25//数字滤波器系数的数量#define SIGNAL1F 1000#define SIGNAL2F 4500#define SAMPLEF 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, -0.018,0.049,-0.02,0.11,0.28,0.64,0.28, -0.11,-0.02,0.049,-0.018,-0.009,0.01, -0.002,-0.002,0.001,0.0,0.0 };//25 个数字滤波器系数, h[n]float fXn[FIRNUMBER]={ 0.0 };//输出信号 x[n]float fInput,fOutput;float fSignal1,fSignal2;float fStepSignal1,fStepSignal2;float f2PI;int i;float fIn[256],fOut[256];int nIn,nOut;main(){nIn=0; nOut=0;f2PI=2*PI;fSignal1=0.0;fSignal2=PI*0.1;fStepSignal1=2*PI/30;fStepSignal2=2*PI*1.4;while (1){fInput=InputWave();fIn[nIn]=fInput;nIn++; nIn%=256;fOutput=FIR();fOut[nOut]=fOutput;nOut++;/* 断点 */if ( nOut=256 ){nOut=0;}}}float InputWave() //生成一个信号，为两种频率的正弦波叠加。{for ( i=FIRNUMBER-1;i0;i-- )fXn[i]=fXn[i-1];fXn[0]=sin((double)fSignal1)+cos((double)fSignal2)/6.0;fSignal1+=fStepSignal1; if ( fSignal1=f2PI )fSignal1-=f2PI;fSignal2+=fStepSignal2;if ( fSignal2=f2PI )fSignal2-=f2PI;return(fXn[0]);}float FIR() //FIR滤波算法{float fSum;fSum=0;for ( i=0;iFIRNUMBER;i++ ){fSum+=(fXn[i]*fHn[i]);}return(fSum);}实验结果