Return Loss between Decawave EVB(Trek1000) and custom design

We have designed our custom PCB for the DW1000 IC. We followed the design guide APH006 for the PCB layout such as the recomended stackup and the recomended layout. We used a 8 layer PCB and thus the stackup it is not the same as the one indicated in the user guide. However, we mantained the top layer and the layer immediately below the same. Moreover, the caracteristics impedances for 50 Ohm and 100 Ohm differential were certificated by the manufacturer.

We have compared the performance of the DECAWAVE board with our design and there are appreciable differences. The transmitted power by both is almost the same, but it is not like that at the reception, i.e. we have measured return losses and we have seen that in our board the value is much worse that for the Decawave.

Where do you think the problem may be? It could be possible to obtain the Decawave’s PCB characteristics? Such as stack up, manufacturer, materials…