A packaged 3 GHz timing interface unit for a laser altimeter system

A Timing Interface Unit (TIU) integrated circuit is implemented in a Ft=45 GHz (Ft) AlGaAs/GaAs HBT process. The TIU was designed for a satellite based laser altimeter system with vertical resolution of 5 cms. The TIU performs two functions: (1) generate coarse count for the time-of-flight of the laser pulse; (2) retiming the return pulse with the clock for the return pulse digitizer and generate the return acknowledge. The TIU has 27-bit ripple counter with synchronous operation up to 5 GHz. The packaged IC was tested up to 3 GHz clock rates and 5 GHz on-wafer testing. The chip dissipates 1.3 W. The TIU IC has been integrated into a prototype data acquisition system developed for laser altimetry.