Is 4-layer PCB always better than 2-layer ?

[sprhawk]

I had a design on 4-layer PCB with nrf51822, then the requirement was changed, then the 2-layer is sufficient for routing.

But I thought 4-layer PCB is better for RF circuit, so I can remain 4-layer PCB with a Ground plane and Power plane.

Is my thought true ? Or I can just use a 2-layer then ?

[James Yu]

As long as you follow the PCB guidelines in the product specifications it should be fine.

A PCB with a minimum of two layers, including a ground plane, is recommended for optimal performance.
On PCBs with more than two layers, put a keep-out area on the inner layers directly below the antenna
matching circuitry (components between device pins ANT1, ANT2, VDD_PA, and the antenna) to reduce the
stray capacitances that influence RF performance. 

So a 2 layer board will be sufficient if you have a pretty solid ground plane with little breaks, otherwise it may be better to go with 4 layers.

[MartinBL]

Here are our reference layouts for nRF51. Notice that they are only 2-layer, but as James says, it doesn't necessarily mean that 2 layers are optimal for your particular application. Here are even more reference designs and there are also some Appnotes and White papers with more or less relevant information.

[sprhawk]

thanks for explanation

[sprhawk]

thanks for explanation