We have a CC1101 for 868MHz communication in a circuit we are currently revising and the matching therefore needs to be tuned again. The person who was in charge of the RF circuits now works somewhere else and I am therefore trying to figure out the matching, but I have a question I hope you can answer.
The CC1101 matching network is implemented using a Johanson 0896BM15A0001E which contains the Balun filter and according to the Design Note DNO25 there should be a LCL filter before connecting to the antenna:
In case the antenna is not 50Ohms and a tuning is needed is it then necessary to insert an extra filter after L122/C123/C124 or should I just measure the impedance at the L122 terminal (picture above) seen from the CC1101 side and tune L122/C123 to make sure that this node is measuring 50Ohms at the desired frequency? Or is the correct way to measure at C124 and make sure this node is 50Ohm?
I hope you can help me, thanks!
