Dual-Band/Dual-Mode Rat-Race/Branch-Line Coupler Using Split Ring Resonators

Mohammad Saeid Ghaffarian,Gholamreza Moradi,Mohammad Mahdi Honari,Rashid Mirzavand,Somayyeh Khajehpour

doi:10.3390/electronics10151812

Mohammad Saeid Ghaffarian, Gholamreza Moradi + Show 3 more

Open Access

https://doi.org/10.3390/electronics10151812

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Abstract

A novel dual-band/dual-mode compact hybrid coupler which acts as a dual-band branch-line coupler at the lower band and as a rat-race coupler at the higher band is presented in this paper. One of the most interesting features of the proposed structure is that outputs of the proposed coupler in each mode of operation are on the same side. This unique design is implemented using artificial transmission lines (ATLs) based on open split ring resonators (OSRR). The low-cost miniaturized coupler could be operated as a dual-band 90° branch-line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz. The proposed coupler could be utilized in the antenna array feeding circuit to form the antenna beam. The structure’s analytical circuit design based on its equivalent circuit model is provided and verified by measurement results.

Highlights

Artificial transmission lines with right/left hand wave propagation characteristics and multi-band functionality can be implemented by loading a host line with shunt inductances and series capacitances [1,2,3], split ring resonators (SRR) or complementary split ring resonators (CSRRs) [4,5,6,7]
In [1], dual-band quarter-wave composite right–left-handed transmission lines (CRLH TL) with −90◦ and −270◦ phase shifts were presented at the operation frequency band
A novel compact dual-band/dual-mode coupler was proposed to operate as a dualband branch line coupler at the low frequency bands (3.3 GHz and 3.85 GHz) and a 180◦ ratrace coupler in the high frequency band (5.3 GHz)

Summary

Introduction

Artificial transmission lines with right/left hand wave propagation characteristics and multi-band functionality can be implemented by loading a host line with shunt inductances and series capacitances [1,2,3], split ring resonators (SRR) or complementary split ring resonators (CSRRs) [4,5,6,7]. A dual-mode coupler can operate identically to either a branch-line coupler (90◦) or a rat-race (180◦) at specific frequencies, as demonstrated in [3]. A brief design of dual-mode/dual-band rat-race and branch-line coupler was presented in [4]. A compact dual-band branch line coupler by using the π-shaped dual transmission lines at two arbitrary frequencies was presented in [14] Another method for designing dual-band operation was based on impedance transformation that can create a structure with operation as a coupler as well as a phase shifter simultaneously [15]. The phase slopes of the coupler branches are engineered until the proposed coupler functions identically to both a dual-band 90◦ hybrid coupler and a 180◦ rat-race coupler at the desired frequency band of operation. The theoretical analysis and synthesis of OSRR TL are first performed the simulation, and experimental results of the proposed coupler are demonstrated to validate the proposed approach

Circuit Model and Implementation of Artificial Transmission by Means of OSSR

Branch Line Coupler

Artificial TLs Design

Accurate Circuit Model and Electromagnetic Simulation of the Proposed Coupler

Parametric Study of the Proposed Coupler

Conclusions