离散时间信号处理（英文版）chp6-第2讲推荐.pptVIP

Type III: Direct form structure for linear-phase FIR SY Delayer: M Multiplier: M/2 M is odd (type II or IV) Direct form structure for linear-phase FIR SY = Direct form structure for linear-phase FIR SY Type II: Delayer: M Multiplier: (M+1)/2 Type IV: Delayer: M Multiplier: (M+1)/2 Direct form structure for linear-phase FIR SY 特点: Type I: M/2+1 Type II: (M+1)/2 Type III: M/2 Type IV: (M+1)/2 Direct form structure for linear-phase FIR SY 实现M阶线性相位FIR 系统所需乘法器个数 相对于同阶数的非线性相位FIR系统的直接型结构，可减少大约一半的乘法器。 Zeros of linear-phase SY: occur in mirror-image pairs Cascade form structure for linear-phase FIR SY If z0 is a zero of H(z), then 1/ z0 is also a zero of H(z). Four cases: If h[n] is real, then zeros of H(z) occur in complex-conjugate pairs, i.e., and are also zeros of H(z). Case 1: fourth-order factor multiplier: 2 Cascade form structure for linear-phase FIR SY Case 2: second-order factor multiplier: 1 Case 3: Cascade form structure for linear-phase FIR SY Case 4: first-order factor multiplier: 0 Cascade form structure for linear-phase FIR SY Cascade form structure for linear-phase FIR SY A linear-phase FIR SY can be implemented as a cascade of first-, second-, and fourth-order factors. For example: direct form: (M=9) cascade form: 2 1 1 1 + + + = 5 multiplier: multiplier: Cascade form structure for linear-phase FIR SY (type II) 6.3 Basic structures for IIR systems Direct Form Cascade Form Parallel Form IIR: 6.3.1 Direct Forms Direct Form I Let Then (realize zeros) (realize poles) Delayer: (M+N) Multiplier: (M+N+1) Direct Form II (Canonic Form) —— minimum number 6.3.1 Direct Forms (realize zeros) (realize poles) Delayer: Multiplier: (M+N+1) 特点: 直接I型结构由两个网络级联：第一个横向结构M节延时网络实现零点，第二个有反馈的N节延时网络实现极点；直接II型结构也由两个网络级联：第一个有反馈的N节延时网络实现极点，第二个横向结构M节延时网络实现零点； 实现N阶IIR系统(一般N≥M) ，直接I型结构需要(N+M)个延时单元；直接II型结构需要N个延时单元，所需延时单元最少，故称为规范型； 系数ak, bk与系统函数的零、极点关系不明显，因而不能很好地对系统频率响应性能进控制。 极点对系数的变化过于灵敏，从而使系统频率响应对系统变化过于灵敏，也就是对有限精度(有限字长)运算过于灵敏，容易出现不稳定或产生较大误差。 6.3.1 Direct Fo