Olxx
Member level 1
Hi everyone,
My question may appear strange to you but I am a newbie in RF, that’s why I’m asking for your help.
I have three-port network with port 1 for input, ports2 and 3 for output. All ports are 50 Ohm. Frequency range 1-2 GHz.
In my application I need to split the incoming signal between ports 2 and 3 with -11dB at port 2 and -8dB at port 3.
Theoretically this is a simple task which requires only 4 resistors. I’ve calculated the traces width according to the 50Ohm requirements taking into account the substrate.
But when I start simulating this simple network (S11, S21, S31) taking into account microstrip lines, microstrip via (connection to ground) model, resistors RF models then the results looks strange for me. It is possible to achieve the required -11/-8 dB at ports 2 and 3 but the S11 became too high. When I try to optimize the resistors values for better S11 then I loose the required output levels. The only way I’ve found to get all parameters (S11, S21, S31) in the range is to change the traces width between resistors. But in this case the traces impedance will not be 50 Ohms! So my question is – does it really matter to have the traces impedance equal to the port impedance if all other parameters will be difficult to adjust?
My question may appear strange to you but I am a newbie in RF, that’s why I’m asking for your help.
I have three-port network with port 1 for input, ports2 and 3 for output. All ports are 50 Ohm. Frequency range 1-2 GHz.
In my application I need to split the incoming signal between ports 2 and 3 with -11dB at port 2 and -8dB at port 3.
Theoretically this is a simple task which requires only 4 resistors. I’ve calculated the traces width according to the 50Ohm requirements taking into account the substrate.
But when I start simulating this simple network (S11, S21, S31) taking into account microstrip lines, microstrip via (connection to ground) model, resistors RF models then the results looks strange for me. It is possible to achieve the required -11/-8 dB at ports 2 and 3 but the S11 became too high. When I try to optimize the resistors values for better S11 then I loose the required output levels. The only way I’ve found to get all parameters (S11, S21, S31) in the range is to change the traces width between resistors. But in this case the traces impedance will not be 50 Ohms! So my question is – does it really matter to have the traces impedance equal to the port impedance if all other parameters will be difficult to adjust?