應用雙耦合線之雙頻結構

Double Coupled-Lines Structure for Dual Band Applications

本文提出一種雙頻段 （dual band） 電路設計方式，以串接兩個耦合線（coupled line） 替換一段傳輸線，利用耦合線之耦合效應改變三倍頻率點以獲得雙頻的效果。電路分析以耦合傳輸線理論推導出傳輸線與耦合線之等效關係及第二頻率點公式。此方法應用於雙頻威爾京森功率分配器 （Wilkinson powerdivider）、鼠圈式功率分配器 （rat-race） 之設計，第一頻率點設計在0.915 GHz，第二頻率點為2.45 GHz。實際電路與模擬結果顯示，電路具有良好的一致性。本電路可以應用於雙頻段射頻標籤系統 （RFID） 和高頻微波電路。

A novel dual band design using two coupled-lines to replace atransmission line section in order to acquire the designed frequencies andform dual band characteristics is proposed. The structure is analyzed bytransmission line theory to obtain the equivalent relation betweencoupled-line and transmission line, the design equation for determining thefirst and the second pass frequency is then obtained. To confirm thedesign procedure, a 0.915/2.45 GHz dual band Wilkinson power dividerand a 0.915/2.45 GHz rat-race hybrid were designed, fabricated, andmeasured. The measured and simulated results show good agreement inthe frequency of interest. The circuits can be used in dual band radiofrequency identification (RFID) systems and microwave circuits.