Circuit Structures and Synthesis Methods of Three Microstrip Dual-Band Couplers

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

The main goal of the proposed project is to develop the circuit structures and synthesis methods of three miniaturized microstrip dual-band couplers. In modern communication systems, microstrip couplers are useful because of they can provide output signals with equal or unequal power ratios and with 90 or 180 phase differences. The branch-line coupler, rat-race coupler, and coupled-line coupler are three popular circuits often used in communication systems. Since they require structures with uniform impedances and specific wavelengths involved, they only can be used for single band applications. For this reason, how to enable single coupler operated in dual bands is a popular research topic recently. In this research, we propose the stepped-impedance-stub line to replace the traditional /4 line for coupler design. By taking the advantage of non-uniform impedance distribution, the stepped-impedance-stub line can have an equivalent 90 electrical length in dual bands. According to the aforementioned, this project is divided into three subsections: (1) Dual-band branch-line coupler synthesis, (2) Dual-band rat-race coupler synthesis, and (3) Dual-band coupled-line coupler synthesis. The proposed stepped-impedance-stub line can have dual-band performance and is smaller than the conventional T-shaped line because of its increased non-uniform impedances. The synthesis method is developed and found that it has two degrees of freedom which can be exploited to miniaturize circuit size and/or replace impractical impedances with more realizable ones. The advantage of wide range of realizable frequency ratio of dual bands is also observed. This research develops three novel microstrip dual-band couplers with stepped-impedance-stub lines. In addition to the formulation and simulation, we will also fabricate and measure practical circuits to demonstrate the capability of the proposed circuit structures.

Project IDs

Project ID:PB9907-12638
External Project ID:NSC99-2221-E182-033
StatusFinished
Effective start/end date01/08/1031/07/11

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