For example: Agilent E4440A or Anritsu 68369
Tektronix Pulse/Data Generators
Tektronix DTG-5274
DATA TIMING GENERATOR; 2.7 GB/S DATA GENERATOR,4SLOTS FOR OUTPUT MODULES,0.2 PS DELAY CONTROL RESOLUTION,CAN CONNECT 1 MASTER AND 1 SLAVE
Manufacturer: Tektronix