MIT 公开课程 信号与系统 Lecture10

1、 6.003: Signals and Systems Frequency Response of a High-Q System As Q increases, the width of the peak narrows. H (s = 1+ s plane 0 1 1 s + Q 0 s 2 0 log |H (j | 1 1 2Q 2 Lecture 10 Check Yourself March 9, 2010 Estimate the “3dB bandwidth” of the peak (assume Q 3. Let l (or h represent the lowest (

2、or highest frequency for which the magnitude is greater than the peak value divided by 2. The 3dB bandwidth is then h l . s plane 0 log |H (j | 1 1 2Q 2 0 1 0 1 1 1 2Q 1 1 21 Q 22 log 1 0 1 2 2 0 1 2Q 1 21 Q 2 2 2 1 0 1 2 log 0 Frequency Response of a High-Q System As Q increases, the phase changes

3、more abruptly with . H (s = 1 1 s 1+ + Q 0 s 2 0 |H (j | 0 /2 1 2 1 0 1 2 log 0 Frequency Response of a High-Q System As Q increases, the phase changes more abruptly with . H (s = 1 1 s 1+ + Q 0 s 2 0 |H (j | 1 1 2Q 2 s plane 0 s plane 0 0 /2 1 1 2Q 1 21 Q 2 1 0 1 2 0 2 log Check Yourself Estimate c

4、hange in phase that occurs over the 3dB bandwidth. H (s = 1 1 s 1+ + Q 0 s 2 0 |H (j | 1 21 Q 2 Summary The frequency response of a system can be quickly determined using Bode plots. Bode plots are constructed from sections that correspond to single poles and single zeros. Responses for each section simply sum when plotted on logarithmic coordinates. s plane 0 0 /2 1 1 2Q 2 1 21 Q log 1 0 1 2 2 0 6 MIT OpenCourseWare 6.003 Signals and Systems Spring 2010 For information about ci