Crystal Ladder Filter

[demetal]

Hi,


i would like to know what is the function of the coupling capacitors seen in the ladder filter.


Thank you.

 

[vfone]

The series capacitors in a crystal ladder filter are needed for tuning at various frequencies offsets from the central frequency of the filter.
Also they affect somehow the input/output impedances of the filter, so the parallel capacitors needs to be adjusted in the same time with the series ones, to keep impedances constant.

Play with this freeware Crystal Ladder Filter program, and see their influence on filter parameters:
https://www.bartelsos.de/index.php?dl_file=KA6HV763W6&skip=true