Broadside-Coupled Microstrip Lines as Low Loss Metamaterial for Microwave Circuit Design

Shaofang Gong,Magnus Karlsson,Xin Xu

doi:10.1155/2019/9249352

Abstract

The entire microwave theory is based on Maxwell’s equations, whereas the entire electronic circuit theory is based on Kirchhoff’s electrical current and voltage laws. In this paper, we show that the traditional microwave design methodology can be simplified based on a broadside-coupled microstrip line as a low loss metamaterial. That is, Kirchhoff’s laws are still valid in the microwave spectrum for narrowband signals around various designated frequencies. The invented low loss metamaterial has been theoretically analyzed, simulated, and experimentally verified in both time and frequency domains. It is shown that the phase velocity of a sinusoidal wave propagating on the low loss metamaterial can approach infinity, resulting in time-space shrink to a singularity as seen from the propagating wave perspective.

Highlights

Microwave theory and techniques, based on Maxwell’s equations, and electronic circuit theory and techniques, based on Kirchhoff ’ electrical current and voltage laws, are traditionally two distinguishable disciplines in both university education and industrial research and development
The above theoretical derivations indicate that the phase velocity of a sinusoidal wave on the metamaterial shown in Figure 1 can be either negative or positive, and it approaches infinity around the transition region of ω0
Both the simulation and experimental results have verified that the phase velocity of a sinusoidal wave can approach infinity at a designated angular frequency ω0 on a broadsidecoupled transmission line with short-circuit stubs, as theoretically described by (26) and (29)

Summary

Introduction

Microwave theory and techniques, based on Maxwell’s equations, and electronic circuit theory and techniques, based on Kirchhoff ’ electrical current and voltage laws, are traditionally two distinguishable disciplines in both university education and industrial research and development. It is possible to converge Maxwell’s equations and Kirchhoff ’s laws for microwave and even mm-wave circuit designs, as shown . In this paper we present a low loss metamaterial structure based on broadside-coupled microstrip lines, which avoids the aforementioned problems It is compatible with traditional transmission line design, e.g., microstrip lines on a planar structure. Based on this low loss metamaterial structure, a detailed study around the transition region from leftto right-handed wave propagations on the metamaterial has been done. A simplified design methodology based on Kirchhoff ’s laws can be utilized for microwave circuitry analyses, when the low loss metamaterial is utilized at various designated frequencies above 1 GHz

Model and Theory

Simulation

Experiment

GHz 2 GHz

Results and Discussion

Conclusion