NRF905 Impedance Matching Network for different medium

[Leonardo Cabral]

Hello everybody

I have a nRF905 circuit sealed in a different medium than air and I am facing an 8 dBm power loss after sealing. I would like to know the following: Is there any modification needed in the impedance matching network since I am working in a different medium? Or, in other words. Is there some component value that must be reviewed to guarantee maximum power transference to the antenna?

Relevant project information:

We use a single ended connection to 50 Ohms antenna. Our schematics and layout are the ones described at the nRF905 datasheet (section 15.3 and 15.4).

The antenna is not under the sealant. There is a 50 Ohms coaxial cable connecting the impedance matching network output and the antenna. This coaxial cable is under the sealant.

The circuit is sealed with a polyurethane sealant. The dielectric constant of the medium is known (and equal to 4.32).

[Øyvind Karlsen]

Hi,

The matching network must be tuned in the usage scenario, with sealant applied in your case. Possibly you could device some keepout over the matching network, or chose another sealant compound.

The antenna and coaxial cable should be fine because of the way they are designed. However the transition to coaxial cable might cause issues as well.

If you need assistance with tuning please create a ticket on MyPage.

Best regards,

Øyvind