Highly Versatile Coplanar Waveguide Line With Electronically Reconfigurable Bandwidth and Propagation Characteristics

[EN] This paper describes a coplanar waveguide coupled to two split-ring resonators that, in turn, are loaded with two different reactive elements. By these means, balanced composite right/left-handed-like (CRLH-like) and also dual balanced CRLH-like (D-CRLH-like) responses can be obtained with the same structure showing opposite propagation characteristics. This behavior is achieved by simply varying one of the reactive elements, i.e., the capacitive or inductive load. The physical behavior of these transmission lines has been successfully explained by means of a single equivalent circuit. Besides, the proposed transmission lines have an extended bandwidth due to the balanced nature of the structure. The bandwidth of these lines can be electronically controlled using varactor diodes reverse-biased by an external dc voltage. Thus, a reconfigurable cell with CRLH-like and D-CRLH-like propagation has been designed and manufactured. The simulated and measured results show fractional bandwidths from 0% (no transmission) to 9.3% for simulations and from 0% (no transmission) to 8.7% for measurements. Undoubtedly, these new proposed transmission lines will be useful for designing reconfigurable devices that can be used in future communication systems such as radar, wireless applications, global positioning systems, or radio-frequency identification systems, among others.This work was supported by the Ministerio de Economia y Competitividad, Spanish Government, under Research Project TEC2013-47037-C05-3-R and Research Project TEC2013-47037-C05-1-R and by the Ministerio de Educacion, Cultura y Deporte under the Fellowship Program for Training University Professors.Martinez Cano, L.; Lucas Borja, A.; Boria Esbert, VE.; Belenguer, A. (2017). Highly Versatile Coplanar Waveguide Line With Electronically Reconfigurable Bandwidth and Propagation Characteristics. IEEE Transactions on Microwave Theory and Techniques. 65(1):128-135. https://doi.org/10.1109/TMTT.2016.2613526S12813565

Analysis of transmission lines loaded with pairs of coupled resonant elements and application to sensors

This paper is focused on the analysis of transmission lines loaded with pairs of magnetically coupled resonators. We have considered two different structures: (i) a microstrip line loaded with pairs of stepped impedance resonators (SIRs), and (ii) a coplanar waveguide (CPW) transmission line loaded with pairs of split ring resonators (SRRs). In both cases, the line exhibits a single resonance frequency (transmission zero) if the resonators are identical (symmetric structure with regard to the line axis), and this resonance is different to the one of the line loaded with a single resonator due to inter-resonator coupling. If the structures are asymmetric, inter-resonator coupling enhances the distance between the two split resonance frequencies that arise. In spite that the considered lines and loading resonators are very different and are described by different lumped element equivalent circuit models, the phenomenology associated to the effects of coupling is exactly the same, and the resonance frequencies are given by identical expressions. The reported lumped element circuit models of both structures are validated by comparing the circuit simulations with extracted parameters with both electromagnetic simulations and experimental data. These structures can be useful for the implementation of microwave sensors based on symmetry properties

Synthesis of Planar Microwave Circuits based on Metamaterial Concepts through Aggressive Space Mapping

RF and microwave applications represent one of the fastest-growing segments of the high performance electronics market, where ongoing innovation is critical. Manufacturers compete intensively to meet market needs with reduced cost, size, weight and many other performance criteria demands. Under this scenario, transmission lines based on metamaterial concepts can be considered a very interesting alternative to the conventional transmission lines. They are more compact (compatible with planar manufacturing processes) and present higher degrees of design flexibility. Furthermore, metamaterial transmission lines can also provide many other unique properties not achievable with ordinary transmission lines, such as dispersion or impedance engineering. Nevertheless, the impact in the industry is still not relevant, mostly due to the complexity of the related synthesis and design procedures. These procedures are mainly based on the engineer’s experience, with the help of costly full-wave electromagnetic (EM) simulators and parameter extraction methods. The aim of this thesis is to contribute to simplify and speed up the synthesis and design procedures of artificial transmission lines. In particular, the lines obtained by periodically loading a conventional transmission line with electrically small resonators, such as split ring resonators (SSRs) or its complementary particle (CSRR). The design procedure is automated by using Space Mapping techniques. In contrast to other alternative methods, real synthesis is found from the circuit schematic (that provides a given target response) and without need of human intervention. Some efforts to make the method practical and useful have been carried out. Given a certain target response, it is determined whether it can be physically implemented with a chosen technology, and hence proceeding next to find the synthesis, or not. For this purpose, a two-step Aggressive Space Mapping approach is successfully proposed. In contrast to other methods, the real synthesis is found from certain target circuit values (corresponding to the equivalent circuit model that characterizes the structure to be synthesized). Different efforts have been carried out in order to implement a useful and practical method. Some of them were focused to determine if, given certain circuit parameters (which determine the target response) and certain given technology specifications (permittivity and height of the substrate, technology limits), that response is physically realizable (convergence region). This technique was successfully formulated and it is known as “Two-Step Aggressive Space Mapping Approach”. In this work, the latest improvements made till date, from the synthesis of basic unit cells until different applications and kinds of metamaterial-based circuits, are presented. The results are promising and prove the validity of the method, as well as its potential application to other basic cells and more complex designs. The general knowledge gained from these cases of study can be considered a good base for a coming implementation in commercial software tools, which can help to improve its competitiveness in markets, and also contribute to a more general use of this technology.Rodríguez Pérez, AM. (2014). Synthesis of Planar Microwave Circuits based on Metamaterial Concepts through Aggressive Space Mapping [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48465TESI

Impedance Transformers

Non

Double-sided open split ring resonator for compact microstrip band-pass filter design

A metamaterial structure, called the double-sided open split ring resonator (DOSRR), which combines two open split ring resonators (OSRRs) aligned over the opposite faces of the substrate in an inverted fashion is presented. A study of this resonator from full-wave electromagnetic and circuit simulations is performed. As with the OSRR cell, the DOSRR cell allows a series connection along a microstrip transmission line and it has a small electrical size. Moreover, the DOSRR cell has the ability to add a transmission zero in the out-of-band region without increasing its size. This DOSRR cell is used for the design of compact microstrip slow-wave type band-pass filters. Two strategies based on circular windows etched in the bottom plane instead of square windows and U-shape slots etched in the microstrip transmission line are designed to increase the stop band and to add extra zeros in order to suppress the spurious band. The experimental results have confirmed the possibilities of this electrically small resonator (DOSRR) and the efficiency of both strategies to improve the out-of-band rejection.The authors gratefully acknowledge Ministerio de Ciencias e Innovación of Spain for financial support of this work under the grant no.: TEC2010-21520-C04-04/TCM

State-of-the-Art of Metamaterials: Characterization, Realization and Applications

Metamaterials is a large family of microwave structures that produces interesting ε and μ conditions with huge implications for numerous electromagnetic applications. Following a description of modern techniques to realize epsilon-negative, mu-negative and double-negative metamaterials, this paper explores recent literature on the use of metamaterials in hot research areas such as metamaterial-inspired microwave components, antenna applications and imaging. This contribution is meant to provide an updated overview of complex microwave engineering for the generation of different types of metamaterials and their application in topical electromagnetic scenarios