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]

[ketiljo]

When you simulate the phase difference on the pins, you will find that this is not 180 degrees. Inside the radio front end, on the PA output in TX mode and on the input of the LNA in RX mode, you will find that the phase difference is close to 180 degrees. 

[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?

[KING JAMES]

[KING JAMES]