hello dear friends.
I've designed a bandpass filter in 140 MHz and 20MHz bandwidth. I've casscaded two 3th order eliptic filter for this purpose.
the resulting insertion loss is about 3 dB in simulation , but Its about 12 dB practically.
it's return loss is very bad in pass band (4~6 dB) and this is the reason for high insertion loss.
So how I can improve the return Loss?
tnx
It's a very simple filter you are designing, I bet you are using LC filter designs. You need to tune inductances (coils) or capacitors (trimmers), or both. You should be able to obtain return loss better than 12 dB easily, if you try hard, you should be able to obtain 20 dB RL for such a simple filter.