nRF52832 ANT pin Impedance

RE: nRF52832 ANT pin Impedance

ketiljo — Thu, 24 Jan 2019 14:53:56 GMT

Measure into the matching network with the chip in TX mode and adjust the values of the matching network , C and L, until you see 50 ohm. You must check the levels of the harmonics as well with a spectrum analyzer.

RE: nRF52832 ANT pin Impedance

bjorn-spockeli — Fri, 04 Jan 2019 15:07:13 GMT

We're still handling our backlog due to Christmas vacation, so there will be some delayes in our replies. I will transfer the case to one of our RF Application Engineers that can assist you with matching your custom antenna to the nRF52832 QFN.

RE: nRF52832 ANT pin Impedance

Sugumar — Fri, 04 Jan 2019 12:55:39 GMT

Please confirm mentioned impedance for nRF52832 QFN is 53 + j66 Ohms ANT pin impedance or recommended Load impedance?

RE: nRF52832 ANT pin Impedance

Sugumar — Fri, 04 Jan 2019 10:11:11 GMT

Is there any update for my below latest query?

RE: nRF52832 ANT pin Impedance

Sugumar — Thu, 03 Jan 2019 14:35:45 GMT

I didn't understand, if I am not following manufacturer recommended dielectric material (FR4) and matching components and Antennas

Then how should I match the antenna port and get best performance for my custom design?

What is the typical steps should I use it to achieve? I know conjugate can be used to do proper impedance matching and even though with the matching LC values able to suppress the harmonics if proper EM simulation is done.

bjorn-spockeli Please suggest how to proceed.

RE: nRF52832 ANT pin Impedance

Steve — Thu, 03 Jan 2019 14:07:50 GMT

So what is the pin impedance and recommended load impedance for the WLCSP? I don't typically assume a conjugate match is ideal unless the manufacturer recommends it, since load impedance can impact power, stability, harmonics, etc, and sometimes the optimal load isn't the conjugate due to these other factors...

RE: nRF52832 ANT pin Impedance

Sugumar — Thu, 03 Jan 2019 12:16:32 GMT

Whether ANT pin impedance for the nRF52832 QFN is 53 + j66 Ohms or Load Impedance?

If Pin impedance is 53 + j66 Ohms is then my load impedance should be 53 - j66 Ohms.

Please confirm.

RE: nRF52832 ANT pin Impedance

bjorn-spockeli — Thu, 03 Jan 2019 11:21:13 GMT

The ANT pin impedance for the nRF52832 QFN is 53 + j66 Ohms.

RE: nRF52832 ANT pin Impedance

Sugumar — Thu, 03 Jan 2019 10:25:20 GMT

What is the ANT pin impedance for QFN package? Since we are using QFN package not WLCSP.

We will incorporate a LPF for harmonics suppression with detailed EM simulation by using our layout.

But we can't follow your eval-board layout and components, Because we are using custom PCB antenna with non 50 Ohm impedance.

So we will match your antenna pin impedance to our antenna impedance using LC but with our impedance values.

To do the same we need the ANT pin impedance or Recommended Load impedance value for QFN Package?

RE: nRF52832 ANT pin Impedance

bjorn-spockeli — Thu, 03 Jan 2019 10:09:46 GMT

[quote user="Sugumar"]If the Load impedance of antenna pin should be 53 + j66 Ohms then the ANT pin impedance should be conjugate of the same 53 - j66 Ohms right?[/quote]

You are correct! However, you should note that the matching network used in our reference design does impedance transformation to 50ohms AND low pass filtering. So in order to stay with in regulatory limits you will need to add the LP filter component to your custom antenna design. Simply matching the impedance is not enough.

RE: nRF52832 ANT pin Impedance

bjorn-spockeli — Thu, 03 Jan 2019 10:03:45 GMT

Yes, the WLCSP package does not have the series inductance from the bonding wire used on the QFN.

RE: nRF52832 ANT pin Impedance

Sugumar — Wed, 02 Jan 2019 14:53:59 GMT

If the Load impedance of antenna pin should be 53 + j66 Ohms then the ANT pin impedance should be conjugate of the same 53 - j66 Ohms right?

This will help us instead of keeping the load as 53 + j66ohms, we will do matching from pin impedance 53 - j66 Ohms to final antenna impedance with matching circuits.

Please confirm, Because our antenna impedance is not 50Ohms.

RE: nRF52832 ANT pin Impedance

Steve — Thu, 17 May 2018 16:13:44 GMT

Is there actually a recommended load somewhere in the spec?

If so, I can't find it. I know that different matching networks are given to get to 50 ohms but to the point about non-ideal components and board parasitics, these are not really transferable to another board design.

RE: nRF52832 ANT pin Impedance

AmbystomaLabs — Wed, 16 May 2018 20:18:11 GMT

There are a few questions here so:

1. Yes antenna port impedance is package dependent. You will notice on the spec the recommended load is a little different for the WLCSP vs. QFN versions.

2. No you can't calculate it like that. For starters your calculation doesn't include the effects of the vias, component to component spacing, it should use real not idealized component physics and also it assumes a 50 ohm strip going into the WLCSP. The designs always have a parasitic inductance going into the chip due to the pin pitch.

Also, you can't assume the recommended antenna load results in a 50 ohm match. Power amplifiers rarely perform optimally in a conjugate match condition. Mis-match is often included to optimize the IP3 and harmonic performance.

On your custom board, your only course of action is to come up with a match that optimally conveys power to your antenna, while maximizing IP3 performance and minimizing harmonic output.

RE: nRF52832 ANT pin Impedance

Steve — Wed, 16 May 2018 18:06:47 GMT

Hello,

I have the same question as noe in the follow up. Is the optimum load impedance of the antenna pin dependent on package for the nRF52832?

Thanks,

Steve

RE: nRF52832 ANT pin Impedance

tomkawal — Wed, 21 Mar 2018 16:38:45 GMT

RE: nRF52832 ANT pin Impedance

noe — Wed, 26 Jul 2017 13:38:49 GMT

This is somewhat confusing for me.

Isn't this package dependent?
In the reference design (let's take the nRF52832CIAA as example) the matching components are L = 3.3nH and C = 1pF

Assuming that these components result in 50Ohm I calculated the impedance of the pin and got 78 + j48 Ohms. The reason why this bothers me is that I'd like to match the nRF and the antenna with one single PI-filter and not with the proposed LC and an additional PI-filter due to size limitation constraints.

RE: nRF52832 ANT pin Impedance

bjorn-spockeli — Thu, 04 May 2017 10:50:22 GMT

Hi Rodrigo,

the load impedance of the antenna pin should be 53 + j66 Ohms.

Best regards

Bjørn