I have made an RF amplifier based on the MiniCircuits PSA4-5043+. The circuit is very similar to the one in the evaluation board by MiniCircuits. The layout was changed a bit but not much, and I am using the suggested bias T. The main difference I would say is that in the input I don't have an RF line but rather a radiation detector installed very close to the amplifier, less than 1 cm away, like this:
which produces fast signals pulses. These radiation detectors I know very well because I have used a lot with a different amplifier.
Now, when I look at the signals in the output with the scope I get this:
The peak looks good, but there is this change in the baseline that I have indicated in red. Zooming out it looks like this:
i.e. a damped low frequency oscillation.The signals are all with different amplitude because of the different energies deposited by the particles in the sensor, but over time it ends up looking like this:
What could be the reason for this?
I am trying to simulate this behavior but I don't think it can be replicated with a linear circuit like this
because the kink in the signal at ~4 ns (see oscilloscope) looks non linear.