短波通訊可利用電離層反射，而完成遠距離通訊之目的。由於電離層的時變特性，不同的時間適用的操作參數也不一樣，於是要有效地利用此頻段來通信，須要先選擇適當的操作參數，而短波預測程式，預估短波頻段中的傳播情形，可提供這面的資訊。
短波頻段中的傳播情形與電離層中的電子密度有關，在一般短波預測軟體中常用經驗模型來表示。VOACAP為一常用的預測程式，吾人以VOACAP程式為基礎，發展適合於一般使用者之圖形操作介面，及改進它所使用的電子密度模型。原本的抛物線模型中，在每一層的連接處會有電子密度不連續的情形，新的模型可避免此種不連續的發生。在這個模型中是把電離層分成三段：(1) F2層是用餘弦函數來表示，(2) E-F段用正切函數來表示，並有F1層出現時要多加入餘弦函數來表示，(3) E層還是用抛物線表示。與量測值比較，改進後的預測值有較少的誤差。

A range of shortwave frequencies will be returned to earth by the ionosphere such that long-distance shortwave communication is accomplished. Because of ionospheric variations, operation parameters are not the same in different time duration. We must select optimized parameters with the aim of utilizing the ionosphere effectively for shortwave radio communications. Shortwave propagation prediction programs can provide such information.

Empirical models are often used to represent the variations of the electron density with height in the ionosphere, since radio propagations are concerned with electron density. We develop a graphical user interface based on VOACAP that is one of the most widely used prediction programs. We also improve the electron density model in VOACAP. A gradient discontinuity occurs in the original parabolic ionospheric model. We incorporate an electron density model that does not contain any gradient discontinuities. In this model the electron density profile is composed of three segments: (1) a cosine F2 layer; (2) an E-F layer comprising a secant function, and optional cosine function to provide an F1 ledge (3) a parabolic E layer. Compared with experimental data, our modified model results in more accurate predictions.

致謝 i
摘要 iii
摘要(英文) iv
目錄 v
圖表目錄 vii
第一章 序論 1
1.1 發展目的 1
1.2 電離層的物理特性 2
1.2.1 電離層結構 3
1.2.2 短波傳播描述 5
1.2.3 電離層通道傳播特性 9
第二章 即時地球物理資料之取得 12
2.1 太陽物理 12
2.1.1 太陽黑子數 12
2.1.2 地磁指數的介紹 13
2.2 網路上即時資料的取得 14
第三章 短波通訊傳播預測模式 18
3.1 預測模式的發展背景 18
3.2 VOACAP具備之功能 21
第四章 計算原理(Calculate Theory) 22
4.1 由路徑幾何特性計算模擬參數 22
4.2 電子密度模態 26
4.2.1 控制點的選擇 27
4.2.2 電子密度的產生 28
4.2.3 虛高的計算 39
4.3 雜訊參數 39
4.4 電離層損失模態 42
4.5 HF系統效能 48
4.6 最大可用頻率 52
4.6.1 最大可用頻率的求法 54
第五章 具有整合介面的執行程式 56
5.1 資料輸入 56
5.2 結果輸出 63
第六章 傳播實例 66
6.1 預測實例探討 66
6.2 模擬與實際值比較 67
第七章 結論 71
參考文獻 72

[1] NTIA, U.S. Spectrum Management Policy: Agenda for the Future. Special Publication 91-23, 1991
[2] NTIA, U.S. National Spectrum Requirements: Projections and Trends. Special Publication 94-31, 1995
[3] NTIA, High Frequency (3–30 MHz) Spectrum Planning Options. Special Publication 96-332, 1996
[4] G. Jacobs, T.J. Cohen, and R. B. Rose, The New Shortwave Propagation Handbook, CQ Communications, Inc., 1995
[5] J. M. Goodman, HF Communications: Science and Technology. Van Nostrand Reinhold, 1992
[6] 黃鐘洺，電波傳播，聯經出版事業公司，民國六十七年
[7] J. G. Proakis, Digital Communications McGRAW-HILL, 1995
[8] CCIR, Second CCIR computer-based interim method for estimating sky-wave field strength and transmission loss at frequencies between 2 and 30 MHz, CCIR Report 252-2 Supplemnent
[9] CCIR, HF propagation prediction method, CCIR Recommendation ITU-R PI. 533-4
[10] G. H. Haydon and D. L. Lucas, “Predicting ionospheric electron density profile,” Radio Science, vol. 3, No. 1, pp. 111-119. Jan. 1968
[11] CCIR, Choice of indices for long term ionosperic predictions, Recommendation 371-6
[12] CCIR, CCIR atlas of ionospheric characteristics, CCIR Report 340-6
[13] CCIR, CCIR atlas of ionospheric characteristics, CCIR Recommendation 434-4
[14] J. R. Dudendy and R. I. Kressman, “Emprical models of the electron concentration of ionospheric and treir value for radio communicatons purposes,” Radio Science, vol. 21, No.3, pp.319-330, June 1986
[15] J. R. Dudeney and P. A. Bradley, ”Determination of repesentative height distributions of the electron concentration in the ionospere,” Radio Science, vol. 11, No. 1, pp.9-11, June 1976
[16] J. R. Dudeney, “The accuracy of simple metods for determining the height of the maximum electron concentration of the F2-layer form scaled ionospreric characteristic,” J. Atmos. Terr. Phy., vol. 45, pp.629-640, Apr. 1983
[17] P. L. Dyson and J. A. Bennett, “A model of the distribution of the electron concentration in the ionosphere and its applicatin to oblique propagation studies,” J. Atmos. Terr. Phy., vol. 50, pp.251-262, Apr. 1973
[18] P. A. Bradley and J. R. Dudeney, “A simple model of the vertical distribution of electron concentration in the ionosphere,” J. Atmos. Terr. Phy., vol. 35, pp.2131-2146, Apr. 1973
[19] J. R. Dudendy, “An improved model of the variation of electron concentration with height in the ionosphere,” J. Atmos. Terr. Phy., vol. 40, pp.195-203, Apr. 1978
[20] J. D. Milsom, “Exact ray path calculations in a modified Bradley/Dudeney model ionosphere.” IEE Proceeding, Pt. H, vol. 132, No. 1, pp. 33-38, Feb. 1985
[21] T. A. Croft and H. Hoogasian, “Exact ray calculations in a quasi-parabolic ionospheric with no magnetic field,” Radio Science, vol. 3, No. 1, pp.69-74, Jan. 1968
[22] D. C. Baker and S. Lambert, “Multiparabolic ionospheric model for SSL application,” Electronics Letters, vol.24 No.7, pp. 425-426, Mar. 1988
[23] D. C. Baker and S. Lambert, “Rang estimation for SSL HF system by means or a multiqusiparabolic ionosperic model,” IEE Proc. Pt. H, vol. 136, pp. 120-125, Apr. 1989
[24] CCIR, Characteristics and applications of atmospheric radio noise data, CCIR Report 322-3
[25] CCIR, Radio noise, CCIR Recommendation ITU-R PI. 372-6
[26] S. Gokhun Tanyer, and Cemil B. Erol, “Boadcast analysis and prediction in the HF band,” IEEE Trans. Broadcasting, vol. 44, pp.226-232, June 1998
[27] CCIR, HF field-strength measurement, CCIR Recommendation P.845-2