Squirtle
Newbie level 6
Hello guys,
I am trying to measure the gain of the LNA with a BPF using VNA. Below you see two block diagrams indicated as figure 1 and figure 2. In figure 1 band pass filter is in series with LNA and it is connected to LNA with arbitrary length of coax. In this diagram the length of the coax between BPF and LNA does not affect the gain of the LNA, we measure the gain as it is expected. However in block diagram of figure 2, the length of the coax between LNA and BPF does affect the gain of the amplifier and it is very annoying trying to find appropriate length of the coax to get the max gain that we obtained in figure 1 without any problem. I know for sure that the problem is with LNA because some other LNA types don't have this problem. Whatever I do, I could not figure out what the problem might be? Any help would be very appreciated.
I am trying to measure the gain of the LNA with a BPF using VNA. Below you see two block diagrams indicated as figure 1 and figure 2. In figure 1 band pass filter is in series with LNA and it is connected to LNA with arbitrary length of coax. In this diagram the length of the coax between BPF and LNA does not affect the gain of the LNA, we measure the gain as it is expected. However in block diagram of figure 2, the length of the coax between LNA and BPF does affect the gain of the amplifier and it is very annoying trying to find appropriate length of the coax to get the max gain that we obtained in figure 1 without any problem. I know for sure that the problem is with LNA because some other LNA types don't have this problem. Whatever I do, I could not figure out what the problem might be? Any help would be very appreciated.