K频段微波测距（KBR）系统是低-低卫星跟踪卫星（SST—LL）重力测量卫星的关键载荷之一，其性能直接影响地球重力场空间变化率的测定结果，而KBR系统中超稳振荡器（USO）的稳定度对KBR系统整体测距精度有着重要影响。文章根据双向测量载波相位对比原理和USO幂率谱模型，对KBR系统进行了建模。首先，描述了测距系统的基本原理、系统功能组成及适用于KBR系统的数学模型；然后，利用Matlab软件对“重力恢复和气候实验”（GRACE）卫星的KBR系统进行了仿真。仿真结果表明，采用该模型和方法后获得的双向测距中误差（RMSE）为9．81μm，与公布的GRACE卫星KBR系统10μm的中误差相符。文章为KBR系统的工程设计提供了仿真分析工具，可为工程应用提供设计参考。%The K band ranging (KBR) system is one of the most important instruments of the low-low satellite-satellite tracing (SST-LL) gravity measurement satellite which directly affects the Earth gravity field space resolution. The stability of ultra stable oscillator (USO) has a great influence on the whole performance of the KBR. Based on the dual one-way ranging principle and USO power law model, a system structure is presented for high precision KBR measurement sim- ulation. The basic principle, function composition and appropriate mathematical models used in the simulation are studied, and a simulation system is proposed to simulate KBR of GRACE with Matlab. The result shows that the root mean square error(RMSE) of dual one-way ranging is 9.81μm, which is the same as that of KBR in GRACE (10μm). The model can be considered as a simulation and analysis tool for KBR system design and a reference for the project application.
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