3. Research on United Tracking Schemes Based on a New Information Frame Format

In a Tracking, Telemetry and Command (TT&C) system for the upper-stage of a launch vehicle, a mass amount of instant and dynamic telemetry information need to be transmitted to the ground station from the launch vehicle. Meanwhile, ranging accuracy is seriously affected because the energy of telemetry information is more than the ranging information. To meet requirements for transmission of different information on the downlink of launch vehicle upper-stage, a new information frame format based on isochronous service and insert service is proposed. Moreover, three united tracking schemes including direct switch, free oscillation switch and accumulation branch assisted switch are proposed. The performance of the three schemes is simulated with MATLAB. The result shows that all three schemes can implement the switch between different loops, but there exists a phase jump at 20 ms both in direct switch and free oscillation switch. Only the accumulation branch assisted switch can switch smoothly. Therefore, it is the best scheme. The research findings are of high significance for practical applications.