对流层散射最坏月转换模式研究

针对目前的最坏月预测模型无法有效反映对流层散射传输损耗的最坏月时间概率分布随地域和气象气候条件变化的特点，结合ITU-R P.617-3和ITU-R P.841-4建议书给出的最坏月预测模型，提出了一种对流层散射传输损耗最坏月时间概率预测方法。通过合理的数学推演和数值优化，该方法得到了对流层散射最坏月与年平均传输损耗的时间概率转换与地面折射率Ns的对应关系。该方法不仅解决了上述2种ITU模型的缺点，而且更加简单实用，适用范围更广。随后，为了验证该方法的准确性和全球适用性，利用该方法模拟了全球对流层散射数据库中各实验链路典型概率(50%、90%、99%)下的最坏月传输损耗，并与实测值和ITU-R P.841模型进行了对比验证。研究结果对对流层散射传播的发展和应用有一定的参考价值。

Conversion model of annual statistics to worst-month statistics of troposcatter

The present worst-month prediction model,however,cannot reflect the me ical characteristics of tro-poscatter propagation accurately.Hence,based on the worst-month prediction models introduced in the recommendation ITU-R P.617-3 and ITU-R P.841-4 respectively,a conversion model of annual statistics to worst-month statistics of tro-poscatter was presented.The corresponding relation between the conversion of annual statistics to worst-month statistics of troposcatter and the refractivity N_sat the earth's surface was derived with the rational n erical calculation and opti-mization method.This model not only solves the disadvantages of the ITU models mentioned above,but also has a better practicability and applicability.Then,using the new model and the trans-horizon propagation loss data banks released by the international telecommunication union(ITU),the worst-month transmission loss for the non-exceedance time percen-tages(50%,90%,99%)of interest are calculated.The prediction results are compared with the recommendation ITU-R P.841 and the trans-horizon propagation loss data banks.The conclusions are helpful for the development and the applica-tion of the troposcatter propagation.