三埠網路之穩定性與不穩定性分析

Abstract

本論文發展三埠網路的穩定性及不穩定性分析方法，是以二埠網路輸入埠與輸出埠的反射係數表示式，作為穩定性及不穩定性分析的基礎。即藉由將一個三埠網路，其中一埠接上負載，例如第三埠接上 成為一含 變數之二埠網路，如具有回饋網路的二埠串接回饋網路就是一例，並在第一章簡介二埠網路的穩定性分析，以期藉由二埠網路特性，研究發展三埠網路之穩定性分析方法。本論文後續章節，將藉由此一含第三埠 的二埠網路，其輸入埠與輸出埠之反射係數 及 表示式，或運用其表示成一含 變數之二埠網路穩定性因子 ，以期對所接負載網路 ，找到造成此二埠網路在輸入埠與輸出埠上，無條件穩定區域及條件不穩定區域的邊界表示式，或條件不穩定區域內最大不穩定曲線的表示式。對一個三埠微波電路設計，其另外二埠，即第一埠及第二埠也可藉由此程序，將其另二埠分別視為負載網路，分別求得其無條件穩定區域邊界、條件不穩定性邊界及條件不穩定區域內最大不穩定曲線，以完整分析三埠網路之穩定性及不穩定性。本論文將推導所得之三埠網路之穩定及不穩定解析式，藉由使用安捷倫ADS電腦輔助設計軟體分別予以實現，以加強該電腦輔助設計軟體的三埠網路穩定性及不穩定性分析能力，提供微波電路設計者的相關設計資訊。

Beginning with the expressions for the input and output reflection coefficients of a two-port network, this dissertation develops the stability and instability analyses of a three-port network by terminating one port, for example the port 3 with load. A two-port series-feedback network is an example of a three-port network with as the terminating network. Chapter 1 then explains the stability conditions and stability factors of a two-port network and a three-port network, respectively. In the following chapters, the unconditional stability boundaries and the conditional instability curves of a two-port network with the third port terminated with are derived with the explicit expressions. This procedure is followed by having each of the other two ports as the terminating network in order to fully characterize the stability and instability of a three-port network. The resulting explicit expressions related to the unconditional stability and the conditional instability of a three-port network are implemented using the Agilent ADS software tool. These derived expressions can not only enhance the computer-aided capability on the stability analysis of a three-port network but also provide useful information for the microwave circuit designer.