Optimum rf impedance to present to transceiver output.

[DashRiprock]

I am tying to match the nRF52840 rf output to my 50 ohm 2.45GHz pcb antenna.  What is the optimum rf impedance for best transmitter/receiver performance?  The markings on the chip are N52840 QIAAC0 1908GK. 

Thankyou,

Doug

[RenanSP]

[I MOVED MY QUESTIONS TO A NEW TICKET]

For now, to dispense with the attenuator, I programmed a harmless carrier of only -12 dBm. Hopefully, the output impedance at -12 dBm is still representative of the impedance at +0 dBm.

With the VNA looking into my radio matching network (reference layout) towards the nrf52810, it reads 130+j25.3 Ohm at the frequency closest to the carrier. That is not too far from Martin's example at +0 dBm (115+j33 Ohms).

But still, why so far from 50+j0 or 70+j0 Ohms? Thanks!