Hi everyone,
I am trying to sort out a design that has following line
Pin -> VGA -> gain block -> driver amp -> PA -> Filter -> directional coupler (coupled signal fed back to VGA control) -> diode PIN switch -> Relay -> Pout
Now problem is that PA can deliver and does deliver 48dBm when filter is not in loop but as soon as the filter gets in the loop power drops back to 43dBm at some frequency points. One more important thing, Filter consists of 5 different filters that are switched in by relays controlled by micro-controller. PA's last stage has a BALUN at it's output to provide the match.
My understanding and conclusion is that because BALUN works on wavelength theory and it's impedance transformation heavily depends on the impedance seen by it on both sides. Now in this case filter is providing a dynamic impedance that is changing with frequency rapidly and so is the match seen by the PA hence it doesn't deliver the power on those particular frequencies. But if this is the case than how can i solve this and if this isn't the case than please guys help me to solve it,, all ideas are welcomed and deeply appreciated.
Kind regards and many thanks