滤波器设计技巧.pptVIP

Feb.2008 DISP Lab 1.main lobe越窄 resolution越高 side lobe 越低越好 2.統計上常用 resolution降一半 main lobe 變寬(trade off) Main lobe變寬(trade off) side lobe降一半 * 1.In fact, the length of window is M-1 2.main lobe和HANN差不多但side lobe降了10dB 3.Hamming 常用在語音處理 * 有參數可調,能得適當的組合 * 優點:To avoid aliasing of the frequency response 缺點:It is nonlinear between discrete-time frequency and continuous-time frequency. FIR Filter Design by Window function technique 1.Rectangular window 2.Triangular window (Bartett window) FIR Filter Design by Window function technique 3.HANN window 4.Hamming window FIR Filter Design by Window function technique 3.HANN window 4.Hamming window FIR Filter Design by Window function technique 5.Kaiser’s window 6.Blackman window 5.Kaiser’s window 6.Blackman window FIR Filter Design by Window function technique FIR Filter Design by Window function technique Window Peak sidelobe level (dB) Transition bandwidth Max. stopband ripple(dB) Rectangular -13 0.9 -21 Hann -31 3.1 -44 Hamming -41 3.3 -53 Blackman -57 5.5 -74 FIR Filter Design by Frequency sampling technique For arbitrary, non-classical specifications of , the calculation of ,n=0,1,…,M, via an appropriate approximation can be a substantial computation task. It may be preferable to employ a design technique that utilizes specified values of directly, without the necessity of determining FIR Filter Design by Frequency sampling technique We wish to derive a linear phase IIR filter with real nonzero . The impulse response must be symmetric where are real and denotes the integer part FIR Filter Design by Frequency sampling technique It can be rewritten as where and Therefore, it may write where FIR Filter Design by Frequency sampling technique with corresponding transform where Hence which has a linear phase FIR Filter Design by Frequency sampling technique The magnitude response which has a maxim