利用任意耦合長度設計平行耦合微帶線帶通濾波器及其微小化

Abstract

本篇論文利用「任意耦合長度」，設計平行耦合微帶線帶通濾波器，達到電路微小化的設計。本文改變一般平行耦合微帶線濾波器的設計流程，先固定每一段耦合線段的線寬、間距，再利用公式求得每段耦合線段所需的耦合長度。為了達到電路微小化及降低成本，參考近年一些文獻以及利用模擬軟體，分析折疊共振腔的共振特性。經由模擬結果發現，可以將電路尺寸大幅地縮小很多，且不影響濾波器的通帶響應。文中設計並製作數個三階與五階的柴式帶通濾波器電路：中心頻率為2.45GHz，比例頻寬10%、20%，，並與實際量測結果比較。

This thesis aims at designing microstrip bandpass filters with compact size. Coupled stages with folded lines are used. To make the effectiveness in reducing the circuit size as efficient as possible, both the width and gap of the coupled microstrip lines are chosen as small as possible. We analyze and compensate the folded resonators and coupled folded resonators, so that bandpass filters can be constructed with coupled multiple folded lines. A scheme for design coupled stages with an arbitrary coupled length is also incorporated into the design, for the convenience of resonator folding. Several Chebyshev filters of orders three and five are fabricated and measured to demonstrate the idea.