Application of RF-MEMS-based split ring resonators (SRRs) to the implementation of reconfigurable stopband filters: a review.

Ferran Martín,Jordi Bonache

doi:10.3390/s141222848

Abstract

In this review paper, several strategies for the implementation of reconfigurable split ring resonators (SRRs) based on RF-MEMS switches are presented. Essentially three types of RF-MEMS combined with split rings are considered: (i) bridge-type RF-MEMS on top of complementary split ring resonators CSRRs; (ii) cantilever-type RF-MEMS on top of SRRs; and (iii) cantilever-type RF-MEMS integrated with SRRs (or RF-MEMS SRRs). Advantages and limitations of these different configurations from the point of view of their potential applications for reconfigurable stopband filter design are discussed, and several prototype devices are presented.

Highlights

Split ring resonators (SRRs) [1] and their complementary counterparts, i.e., complementary split ring resonators (CSRRs) [2], are key building blocks for the implementation of metamaterials [3,4,5]and metamaterial transmission lines [6,7]
SRRs have been loaded with cantilever-type SRRs and applied to the implementation of stopband filters in microstrip technology [21], whereas CSRRs combined with bridge type RF-MEMS have been demonstrated to be useful reconfigurable resonators for the design of stopband filters in coplanar waveguide (CPW) technology [17,18,19,20]
The CSRRs are etched in the central strip of the CPW, and the RF-MEMS are implemented on top of them, as Figure 3 illustrates

Summary

Introduction

Split ring resonators (SRRs) [1] and their complementary counterparts, i.e., complementary split ring resonators (CSRRs) [2], are key building blocks for the implementation of metamaterials [3,4,5]. Due to the negative effective permeability above the SRR fundamental resonance and to the high positive permeability below it, a stop band in the vicinity of that frequency results, and the structure exhibits stopband functionality It has been demonstrated from duality arguments that CSRRs (Figure 1b) can be applied to the design of negative permittivity one-dimensional metamaterials (or metamaterial transmission lines) [7,8]. Has been demonstrated in [9,10], and the circuit model of the unit cell is a multi-terminal network Another strategy for bandwidth enhancement is to consider multiple tuned structures, namely, SRRs, or CSRRs, tuned at slightly different resonance frequencies within the desired stop band [11]. It is demonstrated that there are several alternative configurations of SRR/RF-MEMS combinations useful for the implementation of metamaterial-inspired tunable stopband filters

Stopband Filters Based on Split Rings with RF-MEMS Loading

CSRRs Loaded with Bridge Type RF-MEMS

SRR Loaded with Cantilever Type RF-MEMS

Stopband Filters Based on Cantilever Type SRRs

Discussion and Comparison

Conclusions