I need to find a better way to switch the two impedances. So I will try with a MOSFET, and also another model of pin diode, but new this time to avoid any problem.
When I will receive them, I will be able to first test with a VNA that I have a consistent impedance switching, and then I will start to make a frequency generator and do the first RF backscatter experiments.
Then I will be able to choose the best uC suited for this task. When I receive the parts, I will post again.