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2024 | Book

Planar Microwave Sensors Read chapter Read first chapter

Coupled Structures for Microwave Sensing

Editors: Ferran Martín, Enrique Bronchalo

Publisher: Springer Nature Switzerland

Book Series : Lecture Notes in Electrical Engineering

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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About this book

This book offers a comprehensive and timely review of planar microwave sensors based on coupled structures. Gathering chapters contributed by the most authoritative researchers on this topic, it presents various strategies for sensor performance optimization using coupled lines, directional couplers, and coupled resonators (either distributed or semi-lumped), focusing mainly on sensitivity optimization, and covering chains of coupled resonators as well. The book also reports on analytical methods, design formulas, sensor validation tests, with both simulation and experimental methods, describing some relevant practical applications. Mainly reflecting the research activity carried out by the different contributors in the last years, this book also includes two introductory chapters to help readers who are not very familiar with microwave sensing technologies and coupled structures. All in all, this book addresses advanced graduate students and researchers involved in microwave and sensor technologies, and may be of interest for engineers and professionals as well, working in areas as diverse as wireless sensors and sensor networks, biosensing, chemical sensing, motion control, microfluidics, Internet of Things (IoT), and smart systems.

Table of Contents

Frontmatter
Planar Microwave Sensors
Abstract
In this introductory chapter to planar microwave sensors, the main sensing approaches and working principles are presented, and some representative illustrative prototype examples are reported. Some strategies devoted to sensor performance optimization (manly the sensitivity) are discussed, excluding those strategies based on coupled structures, which are the subject of the subsequent chapters in the book. The chapter also highlights how machine learning can be applied to improve sensor robustness and selectivity. Finally, a section is devoted to outline those aspects of coupled structures that make them useful for sensing.
Ferran Martín
Coupled Planar Microwave Resonators and Transmission-Line Structures
Abstract
This chapter presents the fundamental concepts on coupled microwave structures, including coupled resonators, coupled transmission lines and coupled-line structures. Although many concepts and results here presented have a general validity in the microwave field, the chapter focuses on planar coupled structures, which are the building blocks of the sensors described in the book. The chapter introduces the fundamentals of microwave resonators (lumped and distributed) and coupled planar transmission lines, with special emphasis on coupled identical microstrip lines. Coupled resonators are addressed from the field and circuit approaches, introducing the concepts of electric and magnetic coupling, and resonance-frequency splitting. The last section of the chapter presents the coupled-line directional couplers and two-port coupled-line networks.
Enrique Bronchalo
Permittivity Sensors Based on Coupled Line Sections
Abstract
This chapter focuses on coupled-line section sensors operating under differential excitation utilized for wideband characterization of dielectric materials. Various realizations of sensors designed for the determination of complex permittivity of solid, as well as liquid materials, are presented together with the theoretical analysis, calibration methods, and measurement results. It is shown that utilization of differential excitation in coupled-line-based sensors allows to increase the sensitivity to small-sized materials under test (i.e., having a size comparable with the distance between the sensors’ strips). Thus, these sensors can be utilized for the characterization of small amounts of liquids placed in a microfluidic channel. A comparison between the coupled-line-based sensors and other sensors described in the literature, allowing for the characterization of dielectric materials in a wide frequency range, is also provided.
Ilona Piekarz, Jakub Sorocki
Coupled-Line Directional Coupler Permittivity Sensors
Abstract
Coupled-line directional couplers have played a significant role in microwave systems since their introduction by Oliver [1]. This chapter presents a new application of this component: dielectric constant sensing. To this end, the material under test is placed on the top of a microstrip coupled-line section, and by analyzing the coupler’s response, the dielectric constant of the sample is detected. The response can be either the coupling or isolation levels of the coupler. This sensing approach benefits from high sensitivity, particularly when the isolation level is used. In the following, we will first review the theory of coupled lines and the basics of directional couplers, then present the idea of using a coupler for dielectric constant sensing.
Vahid Nayyeri, Omar M. Ramahi
Reflective-Mode Permittivity Sensors Based on Distributed and Semi-Lumped Coupled Resonators
Abstract
One-port reflective-mode phase-variation permittivity sensors based on weakly coupled resonators (either distributed or semi-lumped) are presented in this chapter. It is demonstrated that by weakly coupling the resonators, the split resonances that appear as consequence of coupling are very close one to each other, and the phase of the reflection coefficient experiences a significant variation (360° if losses are negligible or small) between such frequencies. The consequence is an enhancement in the sensitivity when the device is tuned in between the two resonance frequencies, as demonstrated in the chapter. It is shown that the sensitivity increases as the inverse square of the coupling coefficient, and unprecedented sensitivities are reported in the various examples included in the chapter, where inter-resonator coupling is very weak. The effects of losses in the material under test (MUT), either small or significant, are also studied in the chapter.
Pau Casacuberta, Paris Vélez, Jonathan Muñoz-Enano, Lijuan Su, Ferran Martín
Transmission-Mode Permittivity Sensors Based on Coupled Resonators
Abstract
Loading resonators on a two-port transmission line creates transmission zeros, where each transmission zero corresponds to a resonant mode. By placing an additional resonator with a higher quality (Q) factor close to the existing lower-Q resonator and ensuring that their resonant frequencies overlap, the strong coupling between them makes the original single transmission zero transform into a high-Q transmission peak with a pair of transmission zeros on both sides. The strongly coupled resonators induce this transmission mode. The high Q factor and sensitivity make the transmission mode suitable for two-port transmission-type sensing measurements. In this chapter, we explain the basic theory, design several transmission-mode sensors based on coupled resonators, and use these sensors to detect the permittivity of various samples.
Zhixia Xu, Yi Wang, Shaojun Fang
Analytical Methods to Retrieve the Permittivity by Means of Coupled Resonators
Abstract
Conventional single-resonator sensors perform dielectric properties measurements by means of the well-known perturbation technique, where the resonant frequency and the quality factor are used to extract the complex permittivity values. However, coupled resonators exhibit two resonance frequencies, one corresponding to the odd mode, and the other one to the even mode. This characteristic can be used to measure dielectric properties by correlating the coupling factor of the two resonances to the permittivity. In addition, this can also be used to perform anisotropic measurements, since the geometry of the electric field lines is different for odd and even modes. Therefore, by utilizing the cavity perturbation technique for the different modes, anisotropy can be extracted. In this chapter, coupled-resonator techniques will be addressed for isotropic and anisotropic measurement.
Alonso Corona-Chávez, José Luis Olvera-Cervantes
Planar Microwave Sensors Based on Coupled Ring Resonators and Applications
Abstract
The potential of planar microwave resonators for sensing applications has been signified, when a single resonant structure is exposed to dielectric properties-variant environments. However, enhancing sensing parameters such as sensitivity, selectivity and dynamic range remains a continuing challenge. To address these challenges, coupled microwave resonant structures have been introduced in various microwave sensing applications. It is demonstrated that the quality factor of a coupled resonator system can be improved, and the dynamic range of sensing can be extended before the sensitivity saturation range is reached. In this chapter, the electromagnetic coupling between planar split ring resonators will be discussed. Their performances will be presented in simulation, mathematical analysis and experimental forms, and their outstanding performance in the introduced unique applications will be studied in wired and wireless readout methods. Moreover, it will be shown that not only the electromagnetic coupling of split ring resonators in wired systems enhances the dynamic range of the sensors, but also, in wireless readout systems, it increases the communication distance between an array of coupled passive split ring resonators and an interrogator antenna.
Mohammad H. Zarifi, Omid Niksan, Ali Maleki Gargari, Dima Kilani
Solute Concentration Sensing in Aqueous Solutions with Coupled Microstrip Resonators
Abstract
This chapter presents the application of planar microwave sensors based on coupled resonators for the detection of solute concentration in aqueous solutions. First, the dielectric and conductive properties of these solutions, based on broadband experimental measurements, are presented. Then, different aspects of the sensor design, as well as a sensor circuit model, are exposed. For this model, the theoretical response and the influence of the mutual and self-capacitances of the resonators on the sensitivity are studied. The last section presents two practical examples of sensors applied, respectively, to binary (water-glucose) and ternary (water-sucrose-sodium chloride) solutions.
Benjamin Potelon, Enrique Bronchalo, Carlos G. Juan, Cédric Quendo, Alexis Chevalier
Sensing Using Magnetoinductive Waves
Abstract
The propagation of slow magnetoinductive (MI) waves by virtue of magnetic coupling between resonant elements (called meta-atoms in the terminology of MI waves) enables applications ranging from improved medical imaging to wireless power transfer. A recent development is the use of MI waves in contactless sensing of conductive environments, both in the frequency and in the time domain. The underlying physics in both methods is that a perturbation due to the presence of a conductive object in the vicinity of a meta-atom changes resonant characteristics of the meta-atom and causes reflections of MI waves within the array. In this chapter we focus on time-domain reflectometry, demonstrating accurate defect localisation and characterisation. We discuss potential applications for real-time contactless monitoring of inhomogeneous conductive environments ranging from in-situ 3D printing quality monitoring to medical imaging.
Daffodil Dhayaa, Callum Long, Anna Radkovskaya, Georgiana Dima, Jiaruo Yan, Eleanor O’Hara, Laszlo Solymar, Ekaterina Shamonina
Backmatter
Metadata
Title
Coupled Structures for Microwave Sensing
Editors
Ferran Martín
Enrique Bronchalo
Copyright Year
2024
Electronic ISBN
978-3-031-53861-2
Print ISBN
978-3-031-53860-5
DOI
https://doi.org/10.1007/978-3-031-53861-2