Nordic - printed antenna and impedance matching circuit

[efi malz]

Theranica  current solution already has a printed MIFA antenna and an impedance matching circuit that they have tested and is working very well.

they  would like to keep using their existing antenna and would like to know which impedance matching circuit to use.

 

Thernica current matching circuit and antenna are:

[efi malz]

see customer reply:

To clarify,

Our MIFA antenna is matched to 50 ohm and we do not plan on changing the ground planes. So is the impedance of the IC (both Cypress and Nordic), as well as the traces leading to/from the IC and the antenna.

The circuit shown in our current implementation (1^st picture below) actually serves only a filter.

 

Do you mean to say that the Nordic requires the components as in the 2^nd picture, as the Cypress required the 1^st one, and we should use the components in the 2^nd one now?

[Marjeris Romero]

Hi,

efi malz said:

Do you mean to say that the Nordic requires the components as in the 2^nd picture, as the Cypress required the 1^st one, and we should use the components in the 2^nd one now?

Yes, you should use the circuit on the 2nd one. I will explain why:

I assume the customer is using our nRF52832 chipset. The 0.8 pF and 3.9nH components are then required as shown by our refererence design. They serve both as a matching network for the chip radio but also add additional filtering of harmonics. It's important that the customer copies our the reference layout for the placement of these components as well. See PCB layout guidelines. The capacitor should not be directly connected to the ground plane, but grounded via VSS pin 31. Both components should be place as close to the nRF chip as possible (preferably copy the distances between the components in our reference design). The customer can download the Altium files for our reference desing from Nordic website: https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF52832

If the antenna is matched to 50 ohms then they don't need any extra matching components for the antenna.

Best regards,

Marjeris