is there any restriction for anchors antenna direction ?
also for the tag ?
I mean do we have to put the DWM100 dev board in a specific direction ?
You want to try to keep all of the antennas in the same orientation and you want to keep them as clear from the rest of your electronics (and anything else) as possible.
If you look at page 15 of the datasheet (https://www.decawave.com/sites/default/files/resources/DWM1000-Datasheet-V1.6.pdf) then there are charts showing the antenna gain in different directions. You want to aim for maximum gain between tag and anchor.
Woops. But the same logic applies, decawave have published the antenna pattern for the antenna design used on the DWM1001.