FIR数字滤波器设计.ppt

《FIR数字滤波器设计.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、第七章FIR数字滤波器设计7.1FIRDF的线性相位特征7.2FIRDF设计的窗函数法7.3频率抽样法7.4IIRDF和FIRDF的比较Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.1.线性相位幅频响应相频响应如果：线性相位若:也称线性相位7.1FIRDF的线性相位特性Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright20

2、04-2011AsposePtyLtd.所以：输出是输入的简单移位，移位的大小正比于因此不会发生失真。例：h(n)输出：若：则：线性相位Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.例1：则：没有发生相位失真Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.例2：若：则：发生了相

3、位失真Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.如果系统的相频响应不是线性的，那么系统的输出将不再是输入信号作线性移位后的组合，因此，输出将发生失真。定义：为系统的群延迟(GroupDelay,GD)显然，若系统具有线性相位，

4、则其GD为常数。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.2FIRDF的线性相位条件在绝大部分信号处理的场合，人们都期盼系统具有线性相位，但是，如何实现线性相位？对FIR系统，如果保证：则该系统具有线性相位。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.第一类线性相位条件

5、偶对称奇对称第二类线性相位条件证明Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.1.为奇数令：并利用的对称性，有第一类线性相位条件Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.相位增益所以，只要保证滤波器的系数偶对称，该滤波器必然具有线性相位。令：Evaluationonly

6、.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.增益(Amplitude)与幅度(Magnitude)可正可负，例：总为正增益幅度Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.增益(Amplitude)与幅度(Magnitude)可正可负，例：总为正增益幅度Evaluationonly.Createdwi

7、thAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.2.为偶数令：则：Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5