There are two versions of the DW3000 chip (ignoring package type), the DW3x10 and the DW3x20.
The parts ending in 20 have two antenna ports.
From the DW3000 user manual:
4.2 TDoA and PDoA support
The two-antenna port variants of DW3000 chip can measure the phase of incoming signal. This information can be used to help determine the direction of arrival and location of the transmission when combined with knowledge of the antenna response. More details of how this is performed will be given in an associated application note.
The “associated application note” doesn’t currently seem to be on the decawave web site but I’m guessing it will be very similar to the one for their short lived DW1000 based PDoA modules that achieved a similar result using two DW1000 chips on the same PCB. While that too seems to no longer be available from the main web page I’m sure there are some copies somewhere on the internet.