Research On Key Technologies Of Generalized TT&C Channel Simulator

Tracking, telemetry and command (TT&C) system, which provides reliable TT&Csupports for multifarious spacecrafts with different purposes and operating orbits, is knownas an important part of aerospace engineering to make the spacecrafts operate in normalstates and ensure the space missions be fulfilled successfully. Under the impetus ofaerospace industries, TT&C systems develop rapidly and have taken on tremendousdifferences in many aspects including TT&C system, signal format, operating range, orbitmeasuring precision, and so on. To adequately verify and test the functions andperformances of different satellite-ground TT&C equipments, it is significant to develop thegeneralized TT&C channel simulator that is suitable for arbitrary TT&C system and notdependent on any signal priori information. Under the background of the practical researchproject, this dissertation makes intensive studies on the key technologies of S wavebandgeneralized TT&C channel simulator.The main contents of this dissertation are summarized as follows:1. For high-accuracy test demand of satellite-ground TT&C equipments, two novelgeneralized TT&C channel simulation methods are proposed: equal interval sampling-unequal interval reconstruction method, dynamic interpolation reconstruction method. Theequal interval sampling-unequal interval reconstruction method is in essence to change thehigh-accuracy delay problems of wideband and arbitrary TT&C signal into the high-accuracy delay problems of the known equal-interval sampling clock. The methodgenerates an unequal-interval reconstruction clock, which is consistent with satellite-grounddelay change rules, and control the unequal-interval output of equal-interval samplingsequences to achieve the large-range and high-accuracy dynamic transmission delaysimulation. Dynamic interpolation reconstruction method draws from the theories ofinterpolation reconstruction and delay resampling of bandlimited digital signals. Theessential is to change the high-accuracy delay problems of wideband and arbitrary TT&Csignal into a sort of dynamic digital interpolation operation. Hence, the dynamictransmission delay simulation can be achieved by first indexing and choosing a group ofsamples from stored sampling sequences in dynamic manner, and then implementing acontinuously variable fractional-interval interpolation operation and output in equal interval.The mathematical derivation and system architecture of the two methods are given. Computer simulations and test results show their validity and performance.2. A high-accuracy and high-density simulation parameters calculation method basedon satellite-ground range piecewise polynomial fitting and recursion is presented. Themathematical principle is derived, and the quantization and quantization errors correctingmethods are given. Computer simulation results show that the method has the ability togenerate high-accuracy range and velocity simulation parameters at high-density intervals.3. Aiming at the high-accuracy range and velocity simulation demands andconsidering the effects of time-varying inherent delay of practical simulator on simulationaccuracy, an on-line delay calibration method based on dynamic motion law cancellation isproposed. The method first couples the simulated input signal and output signal to a localpublic channel in real time and coverts frequency into complex baseband. Then thedynamic motion law between the two baseband signals is cancelled by a series of processesincluding time-sharing sampling and storing, dynamic interpolation reconstruction andDoppler modulation. Finally the effects of time-varying inherent delay on the range andvelocity simulation accuracy can be effectively eliminated by estimating the inherent delayfrom the two cancelled signals and modifying the satellite-ground delay change rules. Themathematical derivation and system architecture are given, and simulations are conductedto verify the validity and performance of the method.4. Considering the severe effects of ionospheric dispersion on wideband and ultru-wideband TT&C system, a generalized wideband ionospheric dispersion simulation methodis proposed. In the method, ionospheric dispersive effects on wideband TT&C signal aremodeled as an all-pass nonlinear phase system, which is then decomposed into three newsubsystems: the subsystem with a linear phase passing through zero frequency, thesubsystem with zero-offset and quasi-parabolic nonlinear phase, and the subsystem with aconstant phase. The generalized and high-fidelity ionospheric dispersion simulation can beachieved by cascading the three subsystems.5. For the development requirements of S waveband generalized TT&C channelsimulator, an overall design scheme based on the reconfigurable, expansible and modulardesign idea is presented. Then the functions, design considerations and basic compositionsof each submodule are introduced. The test results show that the distance simulationaccuracy of S waveband generalized TT&C channel simulator can achieve is superior to0.007m (1), and the velocity simulation accuracy is superior to0.0085m/s (1) underthe large-range and high-dynamic simulation scene.