Hello,
I was looking the layout of the Lime SDR 1.2 and I saw that the diff pair of the USB 3.0 dosen’t have return current vias, which could cause some reflections and degrade the signal integrity, may be in next version these could be add with out any extra cost.
And I have a little doubt, the layer 1 has the RF signals and L2 is the reference of those signals, wouldn’t be better have a little closer L1 and L2? (and obviously recalculate the track geometry for the correct impedance) in order to have a better flux cancelation in order to have less EMI problems? I mean you are working with really high frequencies and without any extra cost you will reduce the EMI between the different RF channels and you will improve the EMC of the board.
In the following link you can find an article that I wrote with the explenation of the 2 concepts that I just said, it’s in portuguese, but can be translated into english in the USA flag in the top right corner.
http://www.embarcados.com.br/roteamento-em-projetos-de-alta-frequencia-corrente-de-retorno/
If I’m missing something or you have any suggestion please make it.
Best regards
Javier