How to specify a group filter on an infoengine adapter

I am using Windchill PDMLink Release 13.0 and Datecode with CPS 13.0.2.3. I would like to create a group filter on an infoengine adapter that limits the participant administrator so that it can only find a single group in AD. I added the group.filter property but I can't figure out the format required for the filter itself. I tried just specifying the cn of the group but it just excluded all groups so I'm not sure the format is correct. Could someone advise please?