新型三頻雙工電路與多頻匹配設計

Abstract

本論文前半部份，提出新式雙頻蕈狀結構，利用在蕈狀結構金屬片上附加L型裂口，使蕈狀結構之高階模頻率得以被降低以及控制，進而達到雙頻濾波之效果。該結構被應用於改良三頻雙工環路器之設計，不但降低電路製造之成本，亦使電路性能有效提升。本論文更進一步分析其電路運作機制，藉由化簡電路架構，開發出具備相同電路功能的新型微波電路，三頻雙工T型電路。經比較可發現，該電路擁有較大的頻寬以及較低的介入損耗。 本論文後半部份，則是提出全新的多頻匹配方法，將蕈狀結構結合懸置微帶線的理論延伸至串聯LC共振腔的概念，設計出易於製作的共振腔結構，並利用該結構與多級串接的單殘段匹配網路相結合，達成任意多頻匹配之效果。為驗證匹配之理論，本論文分別以雙頻與三頻平板式單極天線作為負載電路，依照匹配流程進行設計，成功將天線匹配於其共振頻率。

In the first part of this thesis, a novel dual-band mushroom-like structure is presented. By making L-shaped notches on the patch of mushroom-like structure, the high order mode frequency can be significantly reduced and controlled. A modified triplex bi-directional ring-hybrid is realized with dual-band mushroom-like structures. The proposed circuit yields better performance, and the cost of fabrication has been greatly reduced. Furthermore, by simplifying the topology of triplex bi-directional ring-hybrid, a novel microwave circuit called triplex bi-directional T-type circuit is developed, which has the same mechanism with the original circuit. The result shows that the proposed circuit can provide larger bandwidth and lower insertion loss. A multi-band matching network is proposed in the second part of this thesis. We extend the concept of the mushroom-like structure with suspending microstrip line to the series LC resonator, and realize multi-band matching by a combination of the resonator and multi-stage single stub matching networks. To test the presented approach, a dual-band and a tri-band planar monopole are designed to be the load circuits. Following the proposed matching scheme, the load antennas achieve good return loss at their resonant frequencies.