The balun of nrf51822

[KING JAMES]

I simulated the balun of nrf51822 accroding to the referenced design of nrf51822 on the official website.
However,it showed the differential phase of the balun was not 180 degrees.
Please help me to find a solution,thanks.

[KING JAMES]

1.Please tell me the specific description in official document about the impedance of the Nrf51822 RF port and the design of the Balun circuit.

2.When simulating the circuit with ADS,how should the impedance of two RF ports be set respectively？

[ketiljo]

1. See the product specification, chapter 8.5.7

2. The impedance in #1 is what the radio will like to see, yes, not 50 ohm

Note that you're missing the properties of the PCB, like tracks, pads etc, so your results may not be very accurate.

[KING JAMES]

1.Is the theoretical impedance of point A to the ground 50 ohms?

2.I simulated the circuit diagram above and found that the impedance was 28+j*51, not 15+j85.

Is this simulation circuit correct?

If the layout simulation with PCB, can we get 15+j*85 and NRF can work properly?

[ketiljo]

1. Yes

2. No, as said earlier, you need to take the layout into account as well. I don't see that you're using component models. Theoretical components doesn't give correct results. 

 The impedance 15 +j85 is measured on the actual layout with real components, it's not a simulated value. 

[KING JAMES]

I simulated the circuit with the actual PCB Layout and Murata's capacitance,getting the impedance was 2.6+68.7j. What's the cause?And the key point is how to adjust the layout to match to 15 + 85j?