多層微波積體電路之洩漏主模與廣義散射參數分析

Abstract

本論文分成兩大部分。第一部分提出一種新穎的電磁模擬方法，乃結 合全波積分方程技術與根據等效激源原理提出之激發模型。該積分方程用 數值Galerkin程序解答，導致微波電路萃取以廣義散射矩陣表示。嚴謹的 收斂性分析與廣泛地驗證下，證實了所提方法之可靠性及準確性。此新技 術立即顯示它在微波不連續電路問題中，對高階模與多模能作近不連續處 之定量分析。 這種新提出之方法更進一步用來探討非對稱側平面、具 背面金屬之共平面波導其在斷路之模轉換問題，對一入射共平面波導模將 能量轉換至其它兩個主模，類 c 模 與類 □ 模 ，以及轉換至微帶模之 現象，受側平面寬度、不對稱程度、基板厚度與頻率之影響作了詳盡的研 究。理論計算值與量測結果相當地吻合。此外，也探討有關共平面波導不 連續電路上類表面波模之激發問題。 此新技術若與分割方法結合去分 析複雜且較大的微波平面電路時，將可大大地降低對計算時間和記憶空間 之需求，由於它是先個別處理每個較小的分段，再將它們組合而得到整個 電路的網路特性。分別用該全波方法結合分割方法與否去分析一任意平面 結構，其結果比較相當吻合。 本論文第二部分使用嚴謹的全波模匹配 法探討洩漏主模在對稱多層耦合線上之特性。此工作說明這些結構的上蓋 有著重要的影響，而且證實了偶洩漏主模乃一額外的平行板模被存在的金 屬所微擾，而該現象不同於奇洩漏主模之形成乃奇束縛主模的轉換或演變 。 另外，本論文提出一種由HEMT放大器與弧形微帶線組合而成之振盪 器型主動式天線。該微帶線扮演振盪器的回授電路暨輻射元件。兩個微帶 線至槽線之轉移電路用來連結放大器與洩漏波天線回路，因而無須直流阻 隔電容器。該弧形天線的遠場場形以及包含自我混頻功能之主動式天線電 路性能，皆一併在論文中提出。 This thesis consists of two parts. The first part presents a novel electromagnetic simulation technique that incorporates a full-wave space-domain integral equation technique with a proposed excitation model based on the equivalence principle. The integral equation is solved numerically by Galerkin's procedure resulting in the generalized scattering matrix (GSM) descriptions of the microwave circuit de-embedding. Rigorous convergence studies and extensive validity checks confirm the reliability and accuracy of the proposed method. The novel technique immediately demonstrates its obvious application for quantitative near-discontinuity characterization of higher-order modes and multimode associated with microwave circuit discontinuity problems. The newly proposed method is employed further to investigate the mode conversion of a CBCPW open-end discontinuity with unequal side plane widths. The conversion into two additional dominant modes, the c-mode-like mode and the □mode-like mode, and into the transmitted microstrip mode from an incident CPW mode is studied against side plane width, degree of asymmetry, substrate thickness, and frequency. Theoretical results are in excellent agreement with experimental ones. The mode conversion associated with the surface-wave- like mode at discontinuities of CPW is also investigated. When incorporated with the segmentation method to analyze a complex and large microwave planar circuit, the novel technique analyzes individually each smaller segment and then combines them to yield overall network characterization of the composite circuit. This can significantly reduce the requirement of computation time and memory space. Very good agreement is obtained in a comparative study of an arbitrary planar structure analyzed by the full-wave method with and without segmentation, respectively. The second part of the thesis uses a rigorous full-wave mode-matching method, considering finite metal-strip thickness and conductivity, to investigate the leaky dominant modes on symmetric coupled microstrips with and without superstrate and on a finite-width conductor-backed CPW. This work demonstrates the significant effects of the top cover over these structures and proves that the even leaky dominant mode is an additional parallel-plate mode perturbed by the presence of the strips, which is different from the phenomenon that the odd leaky dominant mode is a conversion or evolution from the odd bound dominant mode. Moreover, a HEMT-based amplifier integrated with an arched microstrip line is developed for an oscillator-type active antenna. The microstrip line serves as a feedback circuit of the oscillator as well as a radiating element. Two microstrip-slotline transitions are used for interconnecting the amplifier and the leaky-wave antenna feedback loop, and thus no DC blocking capacitor is required. The far-field patterns of the arched antenna and the circuit performance including the self-mixing feature of the active antenna are presented.