频率偏置对Ka频段圆极化频率复用数传链路的影响

采用国际电信联盟(ITU)的星地链路计算模型,仿真分析Ka频段双圆极化频率复用(简称"圆极化复用")链路可用情况随2个正交射频通道载波中心频率偏置量变化的关系,得出特定链路可用率下频率偏置量与临界接收仰角的定量关系。在此基础上,为了综合衡量频谱利用情况,提出有效频带利用率指标,并依据此指标对地面站的利用方案进行尝试性设计,以达到优化利用频谱资源的效果。研究结果表明:中心频率偏置量与有效频带利用率是对立统一体。增大中心频率偏置量,在特定链路可用率下可增长数传弧段,进而改善链路可用情况,但无法获取最大有效频带利用率。当载波中心频率偏置量为零时,通过选择合适的链路可用率可实现最大有效频带利用率。文章采用的分析方法和提出的有效频带利用率指标,可推广到其他频段的星地数传链路分析中,为Ka频段星地数传系统设计提供参考。

Effect of Frequency Offset on Data Transmission Link of Circularly Polarized Frequency Reuse at Ka-band

This paper adopts the satellite-to-earth propagation model proposed by ITU （International Telecommunications Union）,analyzes the influence on dual circularly polarized frequency reuse link which uses frequency offset scheme,and finds out the quantitative relationship of special link availability between frequency offset figure and critical elevation.To evaluate the spectrum utilization performance synthetically,a figure of effective spectral efficiency is proposed,and a tentative design of data transmission scheme for ground station application is conducted,so that optimized frequency spectrum can be achieved.Simulation results show that frequency offset figure and effective spectral efficiency are opposite unities.For special link availability,data transmission arc increases with frequency offset increasing,but maximum effective spectral efficiency can not be achieved.When frequency offset figure is zero,the maximum effective spectral efficiency can be achieved by choosing proper link availability.The analysis method used and the effective spectral efficiency figure proposed in this paper can be generalized to analysis of satelliteto-earth data transmission link at other bands,and can provide a reference for Ka-band satellite-to-earth data transmission system design.