A CAD methodology for ultra-sharp roll-off elliptic band-stop filter for suppression of adjacent channel interference

A CAD oriented approach for synthesis of passive elliptic filters is outlined. A combination of various techniques leads to a simple user friendly algorithm which can help in designing very high orders of such filters. Also presented is the computer simulation of a typical 9^th degree filter which gives a 70 dB attenuation of f_c/f ratio of 1.1. A bandstop filter is designed with these prototype values and installed in the communication channels of Eastern Railways.