Abstract: For the analysis of existing problem of excessive error rate in satellite communications link transmission performance parameters, this paper proposes a satellite link propagation characteristics model, and according to the basis of traditional extrapolation, proposes a new link budget BPA（Backward Pass Algorithm）. Through reverse derivation computing system carrier-to-noise ratio, fade margin to seek effective isotropic radiated power value of the transmitting end, and the Effective Isotropic Radiated Power（EIRP） value is dynamically adjusted. Simulation results show that, in actual situation, the method under the radiation power of the transmitting terminal to optimize the impact of the different conditions of the region, the antenna elevation angle, meets the system bit error rate at the same time, and improves the system power efficiency.

Key words: satellite communications, backward pass algorithm, Effective Isotropic Radiated Power（EIRP）, bit error rate

摘要： 针对卫星通信链路传输中对性能参数的分析存在系统误码率过大的问题，提出了一种卫星链路传播特性模型，并在传统正推法的基础上，运用一种新的链路预算方法——倒推法（Backward Pass Algorithm）。该方法通过反向推导、计算出系统载噪比、衰减余量来求得发射端的有效全向辐射功率（Effective Isotropic Radiated Power）值，根据不同情况对EIRP进行动态调整，可以更好地提高地面站的信号传输质量。仿真结果表明，实际情况中，该方法可对地区、天线仰角等不同条件影响下发射端的辐射功率进行优化，在满足系统误码率的同时，提高了系统功率利用率。

关键词: 卫星通信, 倒推法, 有效全向辐射功率（EIRP）, 误码率