Commercial Ku-band SATCOM on-the-move using a hybrid tracking scheme

Abstract

The US Army has a requirement for long range communications to lower echelon tactical operations centers (TOCs) on-the-move (OTM). Current terrestrial radios are severely range-limited. The MITRE mission oriented investigation and experimentation (MOIE) project calls for the design and prototyping of an affordable satellite communications (SATCOM) terminal. The platform stabilization subsystem is a key component of the MITRE program. We propose a new hybrid-tracking scheme for antenna stabilization for line-of-sight (LOS) communications to a commercial satellite operating at Ku-band. Harsh terminal platform dynamic conditions while communicating with the satellite necessitate the use of tracking antennas and stabilized platform pedestals. The hybrid tracking system design includes open loop tracking with periodic closed loop updates to correct for drifting of the inertial system. It combines the use of fiber optic gyroscopic (FOG) sensors with RF-based conical gimbal/step scan feedback. While the gyros compensate for the fast vehicle motion, the lower bandwidth RF tracking loop corrects for the low rate/DC drift errors. The novelty in our approach consists of combining these two tracking loops to minimize the tracking scan-loss. The low-cost aspect of our platform stabilization design is credited to the use of FOG sensors. The hybrid design relies heavily on the use of high quality FOGs to track in a "selective-open loop (RF-wise) pointing mode".