s 87.1 Digital Filter Specifications .. We discuss in this course only the magnitude approximation problem There are four basic types of ideal filters with magnitude responses as shown below P(e.) 所P(e) -Oc 0 Oc π0c0 0c冗 HBP(e/o) HBs(edo) -0c2"0cl 0cloc2兀 丌-0c2-0cl Oclc2兀§7.1 Digital Filter Specifications • We discuss in this course only the magnitude approximation problem • There are four basic types of ideal filters with magnitude responses as shown below   –c 0 c 1 HHP(e j)       –1 –c2 –c1 c1 c2 HBP(e j)     1 –c2 –c1 c1 c2 HBS(e j)