Why Nordic chips have differential RF ports?

[mahmoud.tolba]

Hi Nordic Community and Developers,

I'm a beginner in the RF world and I'm designing a small Bluetooth module using nRF51822 to acquire the RF knowledge and to use it in my next projects.

While reading some white papers, I found that many RF IC’s have differential RF ports and a transformation network is required to use a single ended antenna with these IC’s. So we use a balun to transform the signal from balanced to un-balanced configuration.

So I have some questions:

1. Why many RF IC’s have differential RF ports? we have to use some external components like a balun which increase the BOM and complicate the design? I know that the matching network has another tasks like transforming the output impedance of the radio to a 50 ohm antenna and suppressing the harmonics.
2. Is it for the differential antennas like the folded dipole antennas?
3. Which antenna type is the most common, the single ended antennas or the differential antennas?

Waiting for your kind help and useful answers :)

Thanks..

[Andreas]

Hi

Among the reasons there are a lot of RF ICs with differential outputs is the common mode noise rejection and easy implementation of well performing transceiver architectures in CMOS. Differential antennas are perhaps more common with sub-GHz, e.g. loop antennas, which are relatively small.

I do not have any statistics to refer to, but as far as our designs on the nRF51 series are concerned, single-ended antennas are far more common, using either a chip balun or the reference matching network. Both printed monopole antennas, printed meander antennas and ceramic chip antennas are common.

[mahmoud.tolba]

Thanks Andreas for your answer.