The Design of varactor Tuned Semi-elliptic Function Microstrip Filters

As we need to add varactors at the edge of resonators while design varactor tuned filters, so the electromagnetic field will be changed greatly as the control voltage changed, it´s extremely disadvantaged to semi-elliptic function filters as they have special demand on coupling, so we haven´t see any report on voltage controlled semi-elliptic function filters. Through the additional weak couple between the input line and the output line, there will appear two transmission zeros from the normal band-pass filters, and thus achieved a novel type of semi-elliptic function filters; on the other hand, from change the couple structure of the traditional semi-elliptic function filters, we can also achieve varactor tuned semi-elliptic function filters, and thus find a new way for the design of varactor tuned semi-elliptic filters.