頻率高於10 GHz的電磁波，易受雨滴散射導致訊號強度下降，稱為雨致衰減現象。臺灣地區缺乏Ku波段雨衰相關數據，為了提高衛星通訊的穩定及可靠度，需要對雨衰進行測量和分析。本研究自行設計觀測天線系統並詳述其架構，架設於臺南東區(22.998°N, 120.219°E)與新北三峽(24.944°N, 121.372°E)，觀測同步衛星Asiasat 5 (100.5°E, 12.25 GHz)和Telstar 18V (138°E, 12.75 GHz)，新北僅觀測Asiasat 5 (12.25 GHz)。分析2023年3至6月間降雨強度和訊號衰減量，並與國際電信聯盟無線電通訊部門(ITU-R)模型比較，初步結果顯示，自行設計的系統能觀測到訊號強度變化，訊號衰減和降雨有明確相關性。臺南觀測期間內累積0.01%時間降雨率(106 mm/hr)大於ITU-R提供之數值(82 mm/hr)，可能導致12.25 GHz累積0.01%時間觀測衰減量(17.4 dB)大於ITU-R模型計算值(14.05 dB)；12.75 GHz觀測衰減量則非常接近(18.3 dB)；新北觀測衰減量亦非常接近ITU-R模型計算值(14.38 dB)。使用Ku波段通訊受降雨衰減非常明顯，須有足夠的功率餘裕避免通訊中斷，未來若進行更長時間觀測獲得精確數據，將能建立適合臺灣地區的降雨衰減模型。

There are few rain attenuation observations of electromagnetic wave at Ku-band (12 GHz) of satellite communications over Taiwan. In order to enhance the stability and reliability of satellite communication, it is necessary to measure and analyze the rain attenuations for the operational information. This study designs own receiver system and its architecture in detail. Two receivers were set up in Southern Taiwan, East Dist. of Tainan (22.998°N, 120.219°E), and Northern Taiwan, Sanxia Dist., New Taipei City (24.944°N, 121.372°E) for comparisons. The station in Southern Taiwan observes geosynchronous satellites Asiasat 5 (100.5°E, 12.25 GHz) and Telstar 18V (138°E, 12.75 GHz), while the receiver at Northern Taiwan observes only Asiasat 5 (12.25 GHz). The rate of rain and the corresponding radio signal attenuations were analyzed during March and June 2023. The results are also compared with the models of International Telecommunication Union Radiocommunication Sector (ITU-R). Preliminary results indicate that the designed system is capable of observing changes in the intensity of Ku band signals, and there is a clear correlation between the signal attenuation and rainfall. During the observation period in Tainan, the accumulated 0.01% of total observation time had a rain rate of 106 mm/hr, exceeded the value provided by ITU-R of 82 mm/hr, which could lead to an accumulated 0.01% time observation attenuation of 17.4 dB at 12.25 GHz, greater than the ITU-R model calculated value of 14.05 dB. The observation attenuation at 12.75 GHz was very close to ITU-R model (18.3 dB), so was New Taipei City at 12.25 GHz (14.38 dB). Analyses show that satellite communication using the Ku-band is significantly affected by the rain attenuation and sufficient power margin to avoid interruptions is needed. The experimental set up in this study gives glimpse of the regional satellite communication attenuation at Ku band and with longer observation periods and more precise rain data, it is possible to establish a rain attenuation model suitable for Taiwan region.

Bryant, G. H., Adimula, I., Riva, C., & Brussaard, G. (2001). Rain attenuation statistics from rain cell diameters and heights. International Journal of Satellite Communications, 19(3), 263-283. https://doi.org/10.1002/sat.673
Chakravarty, K., & Maitra, A. (2010). Rain attenuation studies over an earth–space path at a tropical location. Journal of Atmospheric and Solar-Terrestrial Physics, 72(1), 135-138. https://doi.org/10.1016/j.jastp.2009.10.018
Choi, D.Y. (2005). Measurement of Rain Attenuation of Microwaves at 12.25GHz in Korea. In: Boutaba, R., Almeroth, K., Puigjaner, R., Shen, S., Black, J.P. (eds) NETWORKING 2005. Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications Systems. NETWORKING 2005. Lecture Notes in Computer Science, vol 3462. Springer, Berlin, Heidelberg. https://doi.org/10.1007/11422778_113
Choi, D. Y., Pyun, J. Y., Noh, S. K., & Lee, S. W. (2012). Comparison of Measured Rain Attenuation in the 12.25 GHz Band with Predictions by the ITU-R Model. International Journal of Antennas and Propagation, 2012, 415398. doi.org/10.1155/2012/415398
Crane, R. K. (1971). Propagation phenomena affecting satellite communication systems operating in the centimeter and millimeter wavelength bands. Proceedings of the IEEE, 59(2), 173-188. https://doi.org/10.1109/PROC.1971.8123
Crane, R. (1980). Prediction of Attenuation by Rain. IEEE Transactions on Communications, 28(9), 1717-1733. https://doi.org/10.1109/TCOM.1980.1094844
Crane, R. K. (1982). A two-component rain model for the prediction of attenuation statistics. Radio Science, 17(6), 1371-1387. https://doi.org/10.1029/RS017i006p01371
Fukuchi, H., and Y. Otsu (1988), Available time statistics of rain attenuation on Earth-space path, IEE Proc., Part H Microwaves Antennas Propag., 135(6), 387– 390.
Hasanuddin, Z. B., Fujisaki, K., Ishida, K., & Tateiba, M. (2002). Measurement of Ku-band rain attenuation using several VSATs in Kyushu Island, Japan. IEEE Antennas and Wireless Propagation Letters, 1, 116-119. https://doi.org/10.1109/LAWP.2002.806048
IEEE Standard Letter Designations for Radar-Frequency Bands. (2020). IEEE Std 521-2019 (Revision of IEEE Std 521-2002), 1-15. doi.org/10.1109/IEEESTD.2020.8999849
ITU-R, (1997), Frequency tolerance of transmitters, Recommendation SM.1045-1, ITU-R Recommendations SM Series, International Telecommunications Union, Geneva.
ITU-R, (2005), Specific attenuation model for rain for use in prediction methods, Recommendation P.838-3, ITU-R Recommendations P Series, International Telecommunications Union, Geneva.
ITU-R, (2013), Rain height model for prediction methods, Recommendation P.839-4, ITU-R Recommendations P Series, International Telecommunications Union, Geneva.
ITU-R, (2017), Characteristics of precipitation for propagation modelling, Recommendation P.837-7, ITU-R Recommendations P Series, International Telecommunications Union, Geneva.
ITU-R, (2017), Propagation data and prediction methods required for the design of Earth-space telecommunication systems, Recommendation P.618-13, ITU-R Recommendations P Series, International Telecommunications Union, Geneva.
ITU-R, (2019), Ionospheric propagation data and prediction methods required for the design of satellite networks and systems, Recommendation P.531-14, ITU-R Recommendations P Series, International Telecommunications Union, Geneva.
Kumar, V. V., Deo, R. C., & Ramachandran, V. (2006). Total rain accumulation and rain-rate analysis for small tropical Pacific islands: a case study of Suva, Fiji. Atmospheric Science Letters, 7(3), 53-58. https://doi.org/10.1002/asl.131
Mandeep, J., & Allnutt, J. (2007). Rain attenuation predictions at Ku-band in South East Asia countries. Progress in Electromagnetics Research-pier - PROG ELECTROMAGN RES, 76, 65-74. https://doi.org/10.2528/PIER07062605
Mandeep, J. S., & Tanaka, K. (2007). Effect of atmospheric parameters on satellite link. International Journal of Infrared and Millimeter Waves, 28(10), 789-795. doi: https://doi.org/10.1007/s10762-007-9269-x
Mandeep, J. S., Hassan, S. I. S., & Tanaka, K. (2008). Rainfall effects on Ku-band satellite link design in rainy tropical climate. Journal of Geophysical Research: Atmospheres, 113(D5). https://doi.org/10.1029/2007JD008939
Mandeep, J. S. (2009a), Comparison of rainfall models with Ku-band beacon measurement. Acta Astronautica, 64(2), 264-271. https://doi.org/10.1016/j.actaastro.2008.06.026
Mandeep, J. S. (2009b), Slant path rain attenuation comparison of prediction models for satellite applications in Malaysia, J. Geophys. Res., 114, D17108, doi:10.1029/2009JD011852.
Olsen, R., Rogers, D., & Hodge, D. (1978). The aRb relation in the calculation of rain attenuation. IEEE Transactions on Antennas and Propagation, 26(2), 318-329. https://doi.org/10.1109/TAP.1978.1141845
Pan, Q. W., & Allnutt, J. E. (2001). Some second-order Ku-band site diversity results on a high elevation angle path in a rainy tropical region. 2001 Eleventh International Conference on Antennas and Propagation, (IEE Conf. Publ. No. 480), doi: 10.1049/cp:20010348.
Pan, Q., Bryant, G. H., McMahon, J., Allnutt, J. E., & Haidara, F. (2001). High elevation angle satellite-to-earth 12 GHz propagation measurements in the tropics. International Journal of Satellite Communications, 19(4), 363-384. https://doi.org/10.1002/sat.675
Ramachandran, V., & Kumar, V. (2004). Rain attenuation measurement on Ku-band satellite TV downlink in small island countries. Electronics Letters, 40(1), 1-2. https://www.proquest.com/scholarly-journals/rain-attenuation-measurement-on-ku-band-satellite/docview/1622326604/se-2
Ramachandran, V., & Kumar, V. (2007). Modified rain attenuation model for tropical regions for Ku-Band signals. International Journal of Satellite Communications and Networking, 25(1), 53-67. https://doi.org/10.1002/sat.846
Sujan Shrestha, Dong-You Choi, (2019), Rain Attenuation Study at Ku-Band over Earth-Space Path in South Korea, Advances in Astronomy, vol. 2019, Article ID 9538061, 12 pages. https://doi.org/10.1155/2019/9538061
公共電視工程部, (2012), HiHD衛星上鏈後單頻網的穩定度分析, 公共電視研究發展部
周恩祥, (2005), Ka波段雨衰減之特性研究, 未出版之碩士論文, 國立中央大學太空科學研究所
張緒萍, (2004), Ka波段雨衰減之分析與研究, 未出版之碩士論文, 國立中央大學太空科學研究所
曾得浩, (2003), 中華衛星一號低軌道衛星Ka波段雨衰減實驗與模型建立, 未出版之碩士論文, 國立中央大學太空科學研究所
曾吉暉, (2005), 台灣北部地區Ka波段降雨衰減模式之研究, 未出版之博士論文, 國立中央大學太空科學研究所