wide band IF amplifier design help
now the problem is that if I get the gain flatness in 1dB ,
the inband return loss will be poor.
This is due to most transistor has high gain and poor gain flatness at low frequency in a relative wide band.
Any advice can help me to catch both gain flatness and good RL?
Use Philips' "Wideband Transistors" with a little bit feedback ( series or parallel or both ).
You have to use a software ( any ) to optimize Input-Output Return Loss and Gain flatness. Take care stability !
For instance you may easily obtain 15dB Power Gain in that band with BFG93A or similar small signal wideband transistor a little bit feedback.
You can catch +/- 0.3dB flatness with a software optimization.
Feedback will correct flatness and return losses simultaneously.
It's not very difficult.. :)
Good Luck
AdLab contains a good two port analysis program. http://home.t-online.de/home/weberconnect/adlab2.htm is where you download the program. It will run for about 20 times. If you pay the S40 US registration fee the feedback function will be activated. You can the do a little cut and try with the feedback.
This set of programs is well worth the S40.
If you have an analysis program with optimization that program can do it all for you.