The Gulf Range Drone Control System (GRDCS) / Drone Formation Control System (DFCS) RF Transponder is an L-Band transmitter/receiver designed to function as a Distance Measuring Equipment (DME) to support GRDCS/DFCS navigation requirements.
The use of Time-Of-Arrival (TOA) measurements to compute distances requires the transponder to reply to uplinked command messages from ground control stations, with precisely timed downlink telemetry messages. The update rate for the data link messages is nominally 10 messages/second. The GRDCS/DFCS RF Transponder is capable of interrogation rates from 20 Hz (50 milliseconds) to 2 Hz (500 milliseconds).
The GRDCS/DFCS RF Transponder supports data link message communication by decoding and transferring uplink command data to the Integrated Flight Controller (IFC) system, and by encoding downlink telemetry data representing aircraft flight control mode status and sensor readings from the IFC. The GRDCS/DFCS RF Transponder communicates with the IFC via EIA RS-485.