Can any one tell me why doubly terminated LC ladder filter are used. What will happen without using input resistance and output load resistance? as shown in figure attached
LC ladder serves a purpose. Without a load, there is no purpose.
I guess with "input resistance" you are referring mistakenly to the "Rs", which is the output resistance of the source/previous stage.
It's a good idea to portray Rsource upstream of the filter, as a reminder of its presence. If it were absent entirely then enormous AC current passes back and forth through C1 (possibly other sections of the filter).
In addition, by varying Rsource it is a way to influence the sharpness of the filter curve.
I think it's less sensitive to component PVT variation.
I search in edaboard to find this post. Can anyone provide some good tutorial or book for design passive RLC ladder filter with transmission zeros?
I have a notch filter designed with this structure but I cannot understand how it is designed in that way. My circuit structure is exactly same as the first post picture shows with extra cap shunt with inductors.