2009-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/705218摘要：被動式相位共軛法(Passive Phase Conjugation methods, PPC)為新穎之等化技術，主要利用聲波傳遞、模態正交特性等性質達成自等化之效益，可應用於淺海波導環境之通訊等化技術。根據研究發現，PPC可作為前置等化器，搭配後置非線性或線性等化器如DFE與LE等，優點在於可大幅降低後置等化器之計算係數數目，甚至可固定其計算係數數目，不因通道時變變化而改變。此類等化系統是利用接收通訊訊號與波導環境脈衝響應之交相關函數來進行通道等化，以降低通訊碼之符間干擾。比較主動式及被動式相位共軛法，兩者均利用聲學傳播特性達到等化之目標。本計劃基於聲學傳播之模態組成特性及被動相位共軛法之理論基礎，觀測淺海環境之通訊成效及等化效果受聲學模態組成影響。研究方法為劃分淺水海域水下氣候，針對其聲波模態場(acoustic mode field)對於被動式相位共軛等化技術所造成之優劣與可適性，希望降低原理論中陣列處理(Array processing)與多通道結合(Multiple-channel combining)的複雜度，基於此模態組成觀測成為降低系統複雜度之依據。<br> Abstract: Underwater acoustic communication in a shallow water waveguide has advanced greatly for commercial and other applications in the past 15 years. The traditional techniques of wireless communication developed in air are adopted in underwater acoustic communication systems, such as adaptive equalizers and phase-lock loop etc... However, the performance of underwater acoustic communication would only be achieved with intolerable computational complexities. Passive-Phase Conjugation (abbreviated as PPC) is a new equalization technique proposed and developed with acoustic propagation physics to overcome the difficulties mentioned above. They are different from the traditional techniques with respect to signal processing. This project studies the performance of the PPC equalizer based on prior knowledge of acoustic field, and the objective is to quantify, predict and explore the robustness and performance of the PPC equalizer with a vertical line array. Analytical derivation will be presented. It shows that the performance of PPC equalizer strongly relates to acoustic mode composition. Experimental data will be collected and simulation results are used to examine and manifest the theory. The result will show that the composition of acoustic modes directly affects the performance of quadrature-demodulation output and the equalized output of passive-phase conjugation. The relationship between the acoustic mode field and the performance of PPC equalizer is identified, which provides a guideline for optimizing combination of least receivers if prior knowledge of acoustic field is possible.被動式相位共軛法聲波模態場陣列處理多通道結合與等化器複雜度Passive Phase ConjugationAcoustic Mode FieldArray ProcessingMulti-channel combiningand Complexity of equalization