nRF52832 ANTENNA

[Tizana]

Hi,

so i was using the NRF51822-QFAC with an external balun and this antenna chip 2450AT43A100E .

now i want to move to the nRF52832 chip and from what i read is that the balun is integrated into the chip which is a good news,

1/ i want to know if the antenna chip 2450AT43A100E still OK for the nRF52832 ? knowing that i want to take advantage of the extra range proposed by the BLUETOOTH 5?

2/ according to the Schematic QFAA QFN48 section inside the datasheet the inductance L1 and the capacitor C3 connected to the ANT output are they the antenna tuning component or are they a simple component that i have to put them there by default?

in case they're not the antenna tuning components should my schema look like the image below ? :

3/ i downloaded the nRF52832-QFAx Reference Layout 1_1 and opened the nRF52832-QFAA project with altuim software. and i want it to check how the antenna track was made and calculate its impedance.

above a screen shot of the values that i got inside altuim :

when i tried to calculate the antenna track impedance using theses values i figure out that the track impedance is equal to 46.2851 Ohm and not 50 Ohm ?

below a screen shot of the calculation :

i even used other online tools to calculate the impedance and had the same result

the only way to get 50 Ohm is to change the clearance to 6 mil,

did i do something wrong? any explanation ?

[AmbystomaLabs]

I disagree with Jorn though on the significance of 2 mm change in electrical length. On a board the wave travels at less than the speed of light due to Er. In this case about 64% of the speed of light. At 2.4GHz every 1.2mm of distance is 10 degrees of rotation around the smith chart. On a smith chart every 360 degree rotation corresponds to half a wavelength. If all these things were 50ohm they would just spin around the center of the smith chart. However, they are not and 10 or 20 degrees will change things considerably.
When you finally do your antenna match just make sure it is conjugate to the nRF (as it appears on your board) and make sure to do the match while it is in any enclosure you are planning. Any plastic, metal or skin if it is worn nearby will change the antenna match.