The balun of nrf51822

RE: The balun of nrf51822

ketiljo — Tue, 23 Apr 2019 14:23:34 GMT

The length of the bonding wires are difference due to the larger die of the QFAC (more memory), meaning that the QFAC has shorter bonding wires and hence less series inductance.

RE: The balun of nrf51822

KING JAMES — Sat, 13 Apr 2019 03:02:38 GMT

RE: The balun of nrf51822

KING JAMES — Sat, 13 Apr 2019 03:00:53 GMT

Why the parameters of QFAC are different ?

RE: The balun of nrf51822

ketiljo — Fri, 12 Apr 2019 12:11:28 GMT

The impedance, looking from the matching network, at A, into the load is 50 ohm. It's _not_ 50 ohm seen from the load into A.

RE: The balun of nrf51822

KING JAMES — Fri, 12 Apr 2019 06:41:47 GMT

Please confirm it to you again.Is the impedance from point A to NRF51822 50 ohms, or the load at point A 50 ohms?

RE: The balun of nrf51822

ketiljo — Wed, 10 Apr 2019 13:44:09 GMT

Sorry, I have no idea what you do wrong here.

Note that even if the impedance you get matches the recommended load impedance, you don't know how the harmonics are going to behave. Only real measurements will show that.

RE: The balun of nrf51822

KING JAMES — Wed, 10 Apr 2019 08:09:01 GMT

RE: The balun of nrf51822

KING JAMES — Wed, 10 Apr 2019 08:04:04 GMT

RE: The balun of nrf51822

KING JAMES — Wed, 10 Apr 2019 08:02:29 GMT

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?

RE: The balun of nrf51822

ketiljo — Mon, 08 Apr 2019 07:32:54 GMT

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.

RE: The balun of nrf51822

KING JAMES — Sat, 06 Apr 2019 10:56:58 GMT

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?

RE: The balun of nrf51822

ketiljo — Fri, 05 Apr 2019 13:45:05 GMT

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.

RE: The balun of nrf51822

KING JAMES — Fri, 05 Apr 2019 13:06:43 GMT

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？

RE: The balun of nrf51822

ketiljo — Fri, 05 Apr 2019 08:57:51 GMT

The optimal load impedance is 15 +j85 ohm. This is not the reciprocal of the output impedance, but the load impedance that gives the highest output power and lowest noise in the RX LNA.

RE: The balun of nrf51822

KING JAMES — Fri, 05 Apr 2019 06:52:55 GMT

What is the output impedance of the nrf51822 Radio Frequency output port?

RE: The balun of nrf51822

ketiljo — Tue, 02 Apr 2019 13:57:49 GMT

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.

RE: The balun of nrf51822

KING JAMES — Mon, 01 Apr 2019 10:00:04 GMT

RE: The balun of nrf51822

KING JAMES — Mon, 01 Apr 2019 09:57:51 GMT