An article has been published in IEEE Access (free, open access IEEE publication) on a 60 GHz front-end for USRP
N2000/N210. There's a video on the abstract page, and a link to the pdf of the article. the video demonstrates
2x2 MIMO using linear polarization:
The authors state they have released the hardware T/R and controlling software as open source. However I've not
been able to yet locate that file:
open_source_60GHz.tar.gz
which is said to be located in a supplemental file released with the article.
-- Tom, N5EG