A SEMI-EMPIRICAL MODEL OF RAIN ATTENUATION AT KA-BAND IN NORTHERN TAIWAN

Combining a two-year measurement and numerical approach, a semi-empirical model has been developed for prediction of rain attenuation at Ka-band in northern Taiwan. This was done using the drop size distribution (DSD) measurement and the extinction coe-cient calculated by T-matrix, followed by regressing with rain attenuation measurements in all seasons. The attenuation due to rain can be estimated by calculating the extinction coe-cient over all of the rain drops within the antenna beam volume. Comparing with the measured data demonstrates that the proposed model proves su-ciently accurate for Ka-band signal attenuation in site speciflc. For purpose of cross reference, we also compared the proposed model with Crane and ITU-R-P838 rain attenuation models. The RMS error and chi-square test shows that the proposed semi-empirical model has better performance to predicted rain attenuation than Crane and ITU- RP383 models, implied that both model predictions may not be quite reliable in some speciflc areas. Analysis suggests that seasonal efiects are strong in signal attenuation due to rain types. It means that rain rate itself is not a quite reliable enough to be the single parameter in the rain attenuation model.