臺灣博碩士論文加值系統

在本論文中，我們針對傳統的雙電波極化方向頻率重複使用方法，在地面環境下的效能進行檢討。由於雙重極化的電波對於地表通道非理想效應的抵抗力較差，因此在系統架構上必須要有所設計及改善，才能抵擋通道的干擾。在論文中，我們引進了正交頻率分頻多工(OFDM)系統的設計概念，利用頻率位移及頻率配置的方法，在兩個極化方向的電波間，再加入了一個正交的維度：正交頻率配置。利用這一簡單的概念，系統的效能可以得到不錯的改善。本論文中，我們分別針對原始的系統架構，及加入了波形整形之後的系統架構進行詳細的分析，並證明此系統架構的確改善傳統架構的效能。

In this thesis, the performance of dual-polarized signals transmitted in the terrestrial radio links is discussed. Because of the imperfection of the terrestrial transmission channel, the dual-polarized signals can be interfered more easily. It's necessary to design a new scheme to improve system performance to resist the channel interference. We apply the concept of the orthogonal frequency division multiplexing (OFDM) systems. By using the frequency shifting and frequency allocation between two different polarized signals, there is one more orthogonal dimension existing in the system. And the system performance is improved. In the thesis, we analyze both the original system (without pulse shaping) and the pulse shaped system, and we prove that the proposed system scheme improves the transmission performance significantly.

1 Introduction............................................................................................................1
2 Survey of Dual-Polarization Frequency Reuse Systems........................................4
2.1 Polarization ......................................................................................................4
2.2 Polarization Rotation (Faraday Rotation)...........................................................7
2.3 Depolarization ..................................................................................................9
2.4 GEO Satellites versus Terrestrial Links...........................................................11
3 The Discussions of OFDM and Its Merits............................................................14
3.1 OFDM History................................................................................................15
3.2 Basic Principles of OFDM...............................................................................15
3.2-1 Parallel Data Transmission and Multiple Carriers.....................................15
3.2-2 Signal Representation of OFDM...............................................................17
3.2-3 Guard Interval and Its Implementation......................................................19
3.2-4 Some System Parameters..........................................................................21
3.2-5 Coded OFDM............................................................................................22
3.3 COFDM Performance Expectation....................................................................23
3.3-1 Channel Model ..........................................................................................23
3.3-2 Multipath/Fading.........................................................................................23
3.3-3 Frequency Offset.........................................................................................24
3.3-4 Carrier Recovery/Equalization.......................................................................24
4 Dual-Polarization Frequency Reuse System with Spectrum
Allocation of OFDM...............................................................................................26
4.1 System Structure ..............................................................................................27
4.2 Channel Model...................................................................................................29
4.3 System Analysis ..............................................................................................30
4.4 Simulation Result and Discussion......................................................................32
5 Dual-Polarization Frequency Reuse System with Pulse
Shaped Spectrum Allocation of OFDM....................................................................37
5.1 System Structure and Channel Model................................................................37
5.1-1 System Structure Description .....................................................................37
5.1-2 Channel Model............................................................................................41
5.2 System Analysis ................................................................................................41
5.2-1 Dependent Amplitude Coefficients..............................................................45
5.2-2 Independent Amplitude Coefficients............................................................46
5.3 System Performance and Discussion......................................................................47
6 Conclusions................................................................................................................55
Appendix I.....................................................................................................................57
Appendix II ..................................................................................................................59
Appendix III..................................................................................................................60
Reference ......................................................................................................................62

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