>Gaussian lowpass vs.Butterworth lowpass -D2(a, 1 H(u.v)=e 20 H(u,v)= 1+D(u,y)/D H(u.v) H(u,v) 1.0 1.0 D。=10 0.667 -D。=20 -几=40 D。=100 ·D(L.) +D(,) ① Gaussian can completely eliminate ringing while Butter worth cannot. ② At the cutoff frequency,Gaussian is not as sharp as Butterworth ① So prefer Butterwoth to Gaussian when tight control of the transition between low and high frequencies about the cutoff frequency is needed ② Prefer Gaussian to Butterworth when no ringing is allowed(e.g.in Medical diagnosis) Gaussian lowpass vs. Butterworth lowpass 2 2 ( , ) 2 ( , ) D u v H u v e      2 0 1 ( , ) 1 ( , ) / H u v n D u v D   ① Gaussian can completely eliminate ringing while Butter worth cannot. ② At the cutoff frequency, Gaussian is not as sharp as Butterworth ① So prefer Butterwoth to Gaussian when tight control of the transition between low and high frequencies about the cutoff frequency is needed ② Prefer Gaussian to Butterworth when no ringing is allowed (e.g. in Medical diagnosis)