In general, yes, shorter is better.
There are, however, exceptions. Sometimes transmission lines of specific length are used for impedance matching purposes, or other effects.
We’ve noticed that it is generally better, for any given distance between DW1000 and antenna, to run the differential pair longer and the single ended line shorter. That is, it is better for the balun to be near the antenna.
The DC block caps need to be ones rated for the frequency, not just generic caps, and not bigger than 0402.
Top side ground plane in the RF section needs to be poured liberally and have lots of vias to the the internal plane. Make sure the balun pins are well grounded.
The PCB material is important, maybe more so than the trace length. Generic FR4 is not so good at 6.5 GHz. There are a class of “slightly premium” PCB materials such as FR408HR, N4000-13, IT-200LK which cost only a little more but perform much better. The high end stuff, like Rogers, isn’t required, but junk FR4 is to be avoided.
Only true way to know what the design does is to make it and test it. At 6.5 GHz, RF is a bit of a black art and seemingly small things can have relatively big impacts.
Mike Ciholas, President, Ciholas, Inc
3700 Bell Road, Newburgh, IN 47630 USA
+1 812 962 9408