Regarding 85070e dielectric slim form probe (of the former dielectric 85070e Agilent KIT), I have some doubts about its maximum operation frequency.
1) In the specifications (attached), I observe that its calculation is made from a complex number. I don't understand the physical reasons of that (Complex frequency?).
2) On second place, I don't know which MUT's permittivity should I use in the divisor, since its a frequency-dependant value. How can I calculate the frequency with that formula if a term of it depends on the result?
I hope someone can help me on this. I am not now sure that the sensor works up to 50 GHz.