Yes / In this paper, we present the design of a compact and highly sensitive microwave sensor based on a metamaterial complementary split-ring resonator (CSRR), for liquid characterization at microwave frequencies. The design consists of a two-port microstrip-fed rectangular patch resonating structure printed on a 20 × 28 mm2 Roger RO3035 substrate with a thickness of 0.75 mm, a relative permittivity of 3.5, and a loss tangent of 0.0015. A CSRR is etched on the ground plane for the purpose of sensor miniaturization. The investigated liquid sample is put in a capillary glass tube lying parallel to the surface of the sensor. The parallel placement of the liquid test tube makes the design twice as efficient as a normal one in terms of sensitivity and Q factor. By bending the proposed structure, further enhancements of the sensor design can be obtained. These changes result in a shift in the resonant frequency and Q factor of the sensor. Hence, we could improve the sensitivity 10-fold compared to the flat structure. Subsequently, two configurations of sensors were designed and tested using CST simulation software, validated using HFSS simulation software, and compared to structures available in the literature, obtaining good agreement. A prototype of the flat configuration was fabricated and experimentally tested. Simulation results were found to be in good agreement with the experiments. The proposed devices exhibit the advantage of exploring multiple rapid and easy measurements using different test tubes, making the measurement faster, easier, and more cost-effective; therefore, the proposed high-sensitivity sensors are ideal candidates for various sensing applications. / This work was supported by the Moore4Medical project, funded within ECSEL JU in collaboration with the EU H2020 Framework Programme (H2020/2014–2020) under grant agreement H2020-ECSEL-2019-IA-876190, and the Fundação para a Ciência e Tecnologia (ECSEL/0006/2019). This project received funding in part from the DGRSDT (Direction Générale de la Recherche Scientifique et du Développement Technologique), MESRS (Ministry of Higher Education and Scientific Research), Algeria. This work was also supported by the General Directorate of Scientific Research and Technological Development (DGRSDT)–Ministry of Higher Education and Scientific Research (MESRS), Algeria, and funded by the FCT/MEC through national funds and, when applicable, co-financed by the ERDF, under the PT2020 Partnership Agreement under the UID/EEA/50008/2020 project.

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]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48465