I have a current loop "antenna" (design supplied by the customer) that's tuned to, guess, 50R :-)
C2 L ----+----||----UUUUU----. | | | | === C1 R esr | R | | GND GND
The esr resistance and L inductance are the current loop plus some added resistance.
Now the environment is somewhat uncontrolled (conductors,...) and the inductance is allowed to change quite a bit (circa 5%) which plays bad games with the matching and I'm trying to find some design that limit input sensitivity to the L parameter.
Since the smith plot with the distance to the perturbing conductors as the parameter almost retraces the frequency plot I had a look into wideband matching (Bode-Fano,...) but I now think this leads no where...
I guess this pb has been addressed by the RFID guys or possibly MRI too but can find no useful hint.
Any info/hint/link/idea is welcomed...