Application of RF-MEMS-Based Split Ring Resonators (SRRs) to the Implementation of Reconfigurable Stopband Filters : a Review

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

Filtros de microondas basados en metamateriales y en resonadores concentrados

Descripció del recurs: el 21-08-2008Consultable des del TDXTítol obtingut de la portada digitalitzadaRecientemente se ha abierto un nuevo campo de investigación en el área del electromagnetismo aplicado y de la ingeniería de microondas basado en el control de las propiedades electromagnéticas de ciertas estructuras periódicas artificiales conocidas como metamateriales. Debido a que las celdas constitutivas de este tipo de estructuras presentan unas dimensiones muy reducidas en términos de longitud de onda es posible diseñar, en base a este concepto, dispositivos que combinen un gran nivel de compactación y elevadas prestaciones. En esta tesis se han utilizado las propiedades de dichos medios para la implementación de filtros de microondas en tecnología planar. Particularmente se han desarrollado técnicas de síntesis que permiten el diseño de filtros con características controlables, en términos de ancho de banda, rizado en la banda de paso, colocación de ceros de transmisión en la banda de rechazo, etc. En este documento se pueden encontrar varios ejemplos de aplicación de estas técnicas, dando lugar a varios prototipos con respuestas en varios rangos de frecuencia, que van desde respuestas de banda estrecha hasta respuestas ultra anchas.In the last years, a new research field in the area of applied electromagnetism and microwave engineering based on the control of electromagnetic properties of artificial structures has taken a great interest. These structures are known as metamaterials. Due to the small dimensions of its constitutive cells it is possible to design, based on this concept, devices that combine high performance and compact dimensions. This thesis concerns the application of metamaterial technology to the synthesis of microwave filters in planar technology. In this document can be found a design methodology for each cell of the structure according to the desired frequency response of the filter (bandwidth, pass band ripple, location of transmission zeroes, etc). This methodology is also applicable to the design of filters with standard frequency responses (Chebyshev, Butterworth, etc). The theoretical work is also supported with experimental results of several prototypes with different bandwidths, from narrow band responses to ultra wide band filters

Dual and broadband power dividers at microwave frequencies based on composite right/left handed (CRLH) lattice networks

CIMITECThis paper proposes a dual-band power divider operating at GHz frequencies and implemented by means of impedance transformers (also called inverters) based on lattice networks and transmission line sections. The dual-band functionality of the proposed device is achieved thanks to the composite right/left handed (CRLH) behavior of the impedance transformers, able to provide −90° and +90° phase shift at the first and second design frequencies, respectively, of the divider. By using such combination of transmission line sections and lattice networks, the characteristic impedance of the impedance transformers is roughly constant over wide bandwidths, with the results of broad operating bands. To demonstrate the possibilities of the approach, a prototype device is designed, fabricated and characterized

Differential microstrip lines with common-mode suppression based on electromagnetic band-gaps (EBGs)

CIMITECA technique for the suppression of the common mode in differential (balanced) microstrip lines, based on electromagnetic band-gaps (EBGs), is presented in this letter. It is demonstrated that by periodically modulating the common-mode characteristic impedance of the line and simultaneously forcing the differential-mode impedance to be uniform (and equal to the reference impedance of the differential ports), the common mode can be efficiently suppressed over a certain frequency band, while the line is transparent for the differential-mode. The main advantage of EBGs, as compared to other approaches for common-mode suppression in differential microstrip lines, is the fact that the ground plane is kept unaltered. Moreover, the design of the differential line is straightforward since the required level of common-mode suppression and bandwidth are given by simple approximate analytical expressions. As a design example, we report a four-stage common-mode suppressed differential line with 68% fractional bandwidth for the common-mode stopband centered at 2.4 GHz, and maximum common-mode rejection ratio (CMRR) of 19 dB at that frequency. Furthermore, we have designed and fabricated a six-stage double-tuned common-mode suppressed differential line in order to enhance the stopband bandwidth for the common mode around 2.4 GHz

Dual-band balanced bandpass filter with common-mode suppression based on electrically small planar resonators

The design of fully planar dual-band balanced bandpass filters with common-mode noise suppression is reported. The proposed filters are based on electrically small resonators coupled through admittance inverters. For design purposes, the circuit models of the considered resonators are reported. The key aspect for selective mode suppression (i.e., common-mode rejection in the differential-mode pass bands) is related to symmetry properties. Thus, for the differential-mode the symmetry plane is an electric wall, and the equivalent circuit for that mode provides dual-band functionality. Conversely, for the common-mode the symmetry plane is a magnetic wall, and the equivalent circuit exhibits a rejection band. As a proof of concept, the design of an order-2 Chebyshev dual-band balanced bandpass filter with center frequencies f₁= 1.8 GHz (GSM band) and f₂=2.4 GHz (Wi-Fi band), fractional bandwidth FBW= 7%, and ripple level LA1= 0.01 dB is reported. Index Terms-Balanced filters, common-mod

Branch line couplers with small size and harmonic suppression based on non-periodic step impedance shunt stub (SISS) loaded lines

Altres ajuts: ICREAThis paper presents branch line couplers with compact size and harmonic suppression based on non-periodic reactively loaded artificial lines. The reactive loading elements of the lines are step impedance shunt stubs (SISSs). Such elements provide transmission zeros, which are useful to efficiently suppressing the harmonic content of the device. Moreover, by virtue of reactive loading, the reported artificial lines exhibit a slow wave effect of interest for device miniaturization. The combination of size, harmonic suppression efficiency, and design simplicity (with a clear design methodology) is of interest within the framework of artificial transmission lines and their application to the optimization of microwave passive components

Interference sources in congested environments and its effects in UHF-RFID systems : a review

In scenario where radio frequency identification (RFID) readers become increasingly common in hand held devices, the radios are prone to several interferences not only from external radio sources but also from the plurality of portable devices that may become more common over time. For that reason it is of interest to well understand how these radio interferences may be influencing a UHF-RFID transceiver working according to EPCglobal Class-1 Gen-2. In particular, in this paper, the combination of interference coming from the self-radio, from other radio systems, such as mobile phone or other RFID reader, is analyzed, and such effects are combined with the appearance of multiple tag antennas interfering each other. A method based on simulation using tag antenna design is presented to evaluate inter-tag interference in a variety of cases. For a better understanding analytic examples are presented to compute such interference interactions within the RFID system

Improved circuit model for left-handed lines loaded with split ring resonators

In this letter, an improved lumped element equivalent circuit model for left-handed lines based on split ring resonators (SRRs) is presented and discussed. It is rigorously demonstrated that although the previously accepted circuit model of these metamaterial transmission lines (a π circuit) provides a good description of device behavior, its electrical parameters do not actually describe the physics of the structure. Conversely, the parameters of the improved equivalent circuit model are representative of the different elements of the structure, including the SRRs, the shunt inductive elements and the host line. It is also shown that the proposed model can be transformed to a πmodel which is formally identical to the previous reported model of SRR-based left-handed lines. With this transformation, the main relevant characteristics of these left-handed lines are perfectly interpreted

Common-mode suppressed differential bandpass filter based on open complementary split ring resonators fabricated in microstrip technology without ground plane etching

A differential (or balanced) bandpass filter based on open complementary split ring resonators (OCSRRs) coupled through admittance inverters is presented in this article. Pairs of OCSRRs are symmet- rically placed in a mirror configuration between the strips of the differential line and are modeled by means of two series connected parallel resonators. For the differential (odd) mode, there is a virtual ground at the connecting plane between the OCSRR pairs, and the structure is roughly described by the canonical model of a bandpass filter, consisting of a cascade of shunt resonators coupled through admittance inverters. It is demonstrated that, through a proper design of the OCSRR stages, the common mode noise in the vicinity of the differential filter pass band can be efficiently suppressed. Due to the differential mode operation of the filter, it is not necessary to incorporate metallic vias to ground the OCSRRs. Moreover, as compared to other differential filters based on OCSRRs, defected ground structures are not present in the proposed filters. To illustrate the potential of the approach, two balanced bandpass filters are designed, fabricated, and characterized

Compact coplanar waveguide power splitter with filtering capability based on slow-wave structures

A compact coplanar waveguide (CPW) power splitter with filtering capability is presented in this paper. The splitter consists of a pair of 70.71 Ω impedance inverters implemented by means of inductively and capacitively loaded slow-wave structures. Such slow-wave structures efficiently shorten the length of the inverters, thereby providing substantial size reduction to the power splitter. The filtering functionality is due to the Bragg effect, related to periodicity. The proposed splitter, designed to be functional at 1 GHz, exhibits good performance at that frequency, with measured return loss of 20.6 dB and insertion loss of 3.15 dB and 3.23 dB at the output ports. Moreover, the suppression level at the first, second and third harmonic frequency is better than 12.4 dB, 34.6 dB and 24.7 dB, respectively. As compared to the length of the ordinary inverters, the length of the constitutive slow-wave impedance is reduced by a factor of tw