Layout design using SMD antenna

[felipe]

Hello

I am doing a PCB design using nRF51422-QFAC chip. I did based on nRF51-DK but now I would like to change for a SMD antenna (2450AT18A100 from Johanson Tech.) instead of a microstrip antenna type.

I am sending two screenshots, one is the schematic with components values and the layout of the RF part.

1. I saw also people using a balun, it is better than the components that I am using?

2. Do I need to add another component or this way I can get the antenna perfect matching?

I appreciate if you can give me advices to achieve a good RF design.

schematic.jpg

layout.jpg

[Dave_couling]

1. You have a discrete balun insteads of a chip balun. Discrete baluns are sensitive to tune, whereas chip Baluns are already done. But they will have greater insertion loss.

2. You need to have a T or Pi network in series with the antenna to tune with a Network Analyzer.

[Håkon Alseth]

Hi,

1. integrated BALUNs are often used for space concerns and ease-of-development (1 component vs. 6). If you follow the reference schematic and layout, the performance is more or less equal in both scenarios.

2. As @Dave_couling says; you will need an antenna tuner (pi-network) between the BALUN output and the antenna input. Other than that, it looks to be in order.

Cheers, Håkon