法分析於多層結構的半空間中來自終端開口附側牆之矩行波導的幅射及其 應用

Abstract

經由各方面的研究，微波幅射度量應用於乳癌的非破壞性早期檢測變得日 益重要。藉由測知天線（緊貼於一損耗性介質(lossy medium)，即幅射干 射儀(radiometer)的探針）的幅射近場分佈(radiated near-field dis- tribution)，即可直接地導出癌細胞的熱幅射信號。本篇論文採用有限差 分時域法來模擬自天線幅射的功率為不同損耗性介質所吸收的情形，即特 定吸收率的計算。同時，透過模擬幅射的過程，天線開口周緣附近的繞射 現象可清楚地觀察到。由天線互易定理，接收比重函數分佈可輕易地由特 定吸收率的空間分佈得知。3.0 GHz(模擬介質是水)及10.0 GHz(模擬介質 是人體組織) 附近的頻段的信號是主要的分析對象。在這兩個頻段，於單 一或多層介質中，特定吸收率分佈的變化是研究的重點。 The application of microwave radiometry becomes gradually impor- tant on the non-invasive and early detection of breast carcinoma through various studies.The radiometric signal can be directly derived from the knowledge of the near field from the antenna which is used as a probe in direct contact with the assumed lossy medium in the radiometric operation.In this thesis,FDTD(finite- difference time-domain)method is proposed to calculate the radi- ated power absorbed in the lossy medium( problem space),this is, specific absorption rate(SAR).Through the process of simulation, edge diffraction which occurs in the vicinity of the antenna- medium boundary is observed.Owning to the antenna reciprocity theorem,the receiving weighting function distribution thus can be esaily acquired from the SAR distribution.Signals from the band around 3.0 GHz(in the analysis of water)and 10.0 GHz(to simulate ture human tissue) are obtained. For both cases,changes of the SAR distribution are presented and studued in problem space.