Non-Volatile CBRAM/MIM Switching Technology for Electronically Reconfigurable Passive Microwave Devices E-Book
Jayakrishnan M. Purushothama
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
This book presents the applications of non-volatile CBRAM/MIM switching technology for electronically reconfigurable passive RF and microwave devices, together with theory and methods for application in rewritable chipless RFID tags. Conductive Bridging Random Access Memory (CBRAM) is a renowned and commercially used non-volatile memory concept. Having evolved over the past few decades, it is currently identified as an efficient non-volatile RF switching technology. This book presents recent research on this topic, focusing on the development of a new generation of low-cost non-volatile RF switches and their applications, demonstrating both high performance and flexibility of implementation. It includes the experimental realization of various prototypes of RF and microwave devices utilizing this technology, along with relevant analysis of mathematical and electrical models, and detailed discussions of future aspects. All devices presented are compatible with mass industrial production at an economically efficient budget through optimized fabrication steps, without the requirement of sophisticated "clean room" processes among them.
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Table of Contents
Cover
Title Page
Copyright
Preface
1 Motivation and Background: RF Switches and the Need for a Non-Volatile RF Switch
1.1. Introduction
1.2. Requirements and definition of a switch at RF and microwave frequencies
1.3. Review of RF and microwave switching technologies
1.4. State of the art of CBRAM/MIM RF switching technology
1.5. Demand for a non-volatile RF switch and selection of CBRAM/MIM technology
1.6. Conclusion
2 Real-World Implementation Challenges of a Low-Cost Non-Volatile RF Switch
2.1. Introduction
2.2. CBRAM-based fully passive solid-state RF switch on classic RF substrates: design and process optimization
2.3. Electrical equivalent model analysis
2.4. Effect of filament resistance of CBRAM switches on RF transmission
2.5. Time stability, switching cycles and other interesting features
2.6. Fabrication technique for realization of CBRAM/MIM RF switches on flexible substrates
2.7. Application example: design and realization of solid-state non-volatile SPDT switch
2.8. Conclusion
3 Solid-State Rewritable Chipless RFID Tags: Electronically Rewritable RF Barcodes
3.1. Introduction: chipless RFID technology
3.2. Chipless RFID reader system used in this experiment
3.3. Realization of solid-state electronically rewritable chipless RFID tags
3.4. Effect of CBRAM/MIM filament resistance on RCS characteristics of presented electronically rewritable resonators
3.5. Electrical equivalent model of electronically rewritable chipless RFID tags
3.6. Discussion of data encoding strategies for electronically rewritable chipless RFID tags based on CBRAM/MIM technology
3.7. Advantages of using integrated CBRAM/MIM switches for chipless RFID applications
3.8. Conclusion
4 Fully Passive Solid-State Electronically Reconfigurable Filter and Antenna Models
4.1. Introduction
4.2. CBRAM-MIM switches for electronically reconfigurable filter applications
4.3. MIM switches for electronically pattern reconfigurable antenna applications
4.4. Advantages of using proposed CBRAM RF switch technology for reconfigurable antenna and filter applications
4.5. Conclusion
Conclusion
Appendix
A.1. Observation of conductive filament formation in CBRAM/MIM switching cells
References
Index
End User License Agreement
List of Illustrations
Chapter 1
Figure 1.1. Ohmic contact type MEMS RF switch in series configuration
Figure 1.2. Capacitive contact type MEMS RF switch in shunt configuration on a C...
Figure 1.3. PIN diode: (a) layer architecture of a typical PIN diode; (b) electr...
Figure 1.4. Application of PIN diodes as switches in RF circuit: (a) series mode...
Figure 1.5. Simplified layer architecture of an N-channel field effect transisto...
Figure 1.6. Application of FETs as RF switches in a single pole double throw (SP...
Figure 1.7. Concept of relation among electric charge (q), magnetic flux (ϕ), vo...
Figure 1.8. Illustration of crystalline (low resistance) to amorphous (high resi...
Figure 1.9. Topology of a phase change material-based RF switch on a co-planar t...
Figure 1.10. Layer architecture of a typical CBRAM/MIM switch and its working me...
Figure 1.11. Nanoionics-based RF switch (redrawn from Nessel et al. 2008). (a) T...
Figure 1.12. RF performance characteristics of nanoionics-based RF switch shown ...
Figure 1.13. Nanoscale memristive RF switch (redrawn from Pi et al. 2015). (a) T...
Figure 1.14. RF performance characteristic of memristive RF switch, shown in Fig...
Figure 1.15. Core areas of application of a non-volatile RF switch. For a color ...
Chapter 2
Figure 2.1. (a) The conductive bridging CBRAM/MIM switch, (b) SET, (c) RESET and...
Figure 2.2. Filament formation in a copper–nafion–aluminum planar CBRAM/MIM swit...
Figure 2.3. A general comparison of CBRAM technology with other well-established...
Figure 2.4. Chemical structure of nafion
Figure 2.5. Photograph of copper-nafion-aluminum CBRAM/MIM switch on FR-4 substr...
Figure 2.6. DC pulse waveform used to operate CBRAM/MIM switches
Figure 2.7. First 130 switching cycles of one typical cell of copper-nafion-alum...
Figure 2.8. The shunt mode CPW RF switch. The MIM switch is integrated by sandwi...
Figure 2.9. Cross-section view of the CPW shunt mode RF switch showing the MIM s...
Figure 2.10. Simulated S-parameters (full wave) of CBRAM/MIM-based 50 Ω CPW shun...
Figure 2.11. Possible fragile soft spots and step discontinuity due to thickness...
Figure 2.12. Photograph of the fabricated switch showing the microphotograph of ...
Figure 2.13. DC voltage waveform used for operating the switch. The switch is in...
Figure 2.14. DC current waveform measured along the current path of switch durin...
Figure 2.15. Experimentally obtained S-parameters of CBRAM-based CPW shunt mode ...
Figure 2.16. Experimentally obtained S-parameters of CBRAM-based CPW shunt mode ...
Figure 2.17. Electrical equivalent model of CBRAM/MIM switch attached to a CPW l...
Figure 2.18. S21 characteristics of the electrical equivalent model of the CBRAM...
Figure 2.19. S11 characteristics of electrical equivalent model of the CBRAM-bas...
Figure 2.20. Effect of filament resistance of CBRAM/MIM cell on RF transmission....
Figure 2.21. Experimentally observed RF attenuation characteristics for differen...
Figure 2.22. Time stability of set/reset states of a CBRAM/MIM switch
Figure 2.23. Design of a CBRAM-based RF switch using microstrip transmission lin...
Figure 2.24. Simulated S-parameters of CBRAM/MIM-based RF switch on microstrip l...
Figure 2.25. CBRAM-based CPW shunt mode RF switch on paper substrate. Inset in b...
Figure 2.26. Three-step process used for realization of CBRAM-based RF switches....
Figure 2.27. CPW shunt mode RF switch on paper substrate with microphotograph of...
Figure 2.28. Experimentally observed S-parameters of a CBRAM-based CPW shunt mod...
Figure 2.29. Topology of CBRAM/MIM-based SPDT switch. Inset in green border show...
Figure 2.30. Photograph of fabricated CBRAM-based electronically reconfigurable ...
Figure 2.31. RF transmission characteristics of fabricated CBRAM-based non-volat...
Figure 2.32. Isolation characteristics of fabricated CBRAM based non-volatile SP...
Chapter 3
Figure 3.1. Block diagram of RF equipment setup similar to bistatic radar used f...
Figure 3.2. Photograph of bistatic radar setup used for RCS measurement of chipl...
Figure 3.3. Block diagram of a modern compact chipless RFID reader (redrawn from...
Figure 3.4. Geometry of electronically rewritable resonator for chipless RFID ta...
Figure 3.5. Photograph of fabricated electronically rewritable chipless RFID tag...
Figure 3.6. Experimentally measured and simulated (full-wave) RCS response of el...
Figure 3.7. Experimentally measured and simulated (full-wave) RCS response of el...
Figure 3.8. Topology of electronically rewritable resonator for chipless RFID ap...
Figure 3.9. Photograph of fabricated electronically rewritable chipless RFID tag...
Figure 3.10. Experimentally measured RCS response of electronically rewritable c...
Figure 3.11. Simulated (full-wave) RCS response of electronically rewritable chi...
Figure 3.12. Simulated RCS response of a single electronically rewritable resona...
Figure 3.13. Multiscatterer-based chipless RFID tag using “C”-shaped resonators
Figure 3.14. Representation of resonance frequency of scattering resonator-based...
Figure 3.15. Representation of resonance frequency of scattering resonator-based...
Figure 3.16. Electrical equivalent model of “C”-shaped multiresonator-based chip...
Figure 3.17. Electrical equivalent model of electronically rewritable “C”-shaped...
Figure 3.18. Response of electrical equivalent model of Tag 1 from section 3.3.1...
Figure 3.19. Response of electrical equivalent model of Tag 2 from section 3.3.1...
Figure 3.20. Response of electrical equivalent model of electronically rewritabl...
Figure 3.21. Variation of resonance frequency of an electronically rewritable re...
Figure 3.22. Resonance frequency map of rewritable resonator for variation of CM...
Figure 3.23. Geometry of electronically rewritable resonator for chipless RFID t...
Figure 3.24. “Crisscross” arrangement of resonance frequencies in an electronica...
Figure 3.25. “Tuned out” arrangement of resonance frequencies in an electronical...
Figure 3.26. Concept of frequency shift coding used in chipless RFID tags, and a...
Figure 3.27. Illustration of concept of proposed electronically rewritable chipl...
Chapter 4
Figure 4.1. Topology of proposed electronically reconfigurable band-stop filter....
Figure 4.2. Photograph of fabricated electronically reconfigurable shorted stub-...
Figure 4.3. Photograph of fabricated electronically reconfigurable open stub-bas...
Figure 4.4. Experimentally obtained S21 response of electronically reconfigurabl...
Figure 4.5. Experimentally obtained S11 response of electronically reconfigurabl...
Figure 4.6. Experimentally obtained S21 response of electronically reconfigurabl...
Figure 4.7. Experimentally obtained S11 response of electronically reconfigurabl...
Figure 4.8. Electrical equivalent model of electronically reconfigurable shorted...
Figure 4.9. Surface current distribution of electronically reconfigurable shorte...
Figure 4.10. Surface current distribution of electronically reconfigurable short...
Figure 4.11. S21 response of electrical equivalent model of electronically recon...
Figure 4.12. S11 response of electrical equivalent model of electronically recon...
Figure 4.13. Electrical equivalent model of electronically reconfigurable open s...
Figure 4.14. Surface current distribution of electronically reconfigurable open ...
Figure 4.15. Surface current distribution of electronically reconfigurable open ...
Figure 4.16. S21 response of electrical equivalent model of electronically recon...
Figure 4.17. S11 response of electrical equivalent model of electronically recon...
Figure 4.18. Resonance frequency as a function of C
MIM
for electronically reconf...
Figure 4.19. Resonance frequency calculated using [4.1]–[4.3] for set (low imped...
Figure 4.20. Resonance frequency calculated using [4.1]–[4.3] for reset (high im...
Figure 4.21. Topology of proposed electronically reconfigurable band-pass filter...
Figure 4.22. Simulated (full-wave) RF response of electronically reconfigurable ...
Figure 4.23. Topology of electronically reconfigurable band-stop filter with mul...
Figure 4.24. Simulated (full-wave) RF response of electronically reconfigurable ...
Figure 4.25. Topology of proposed model of band-stop filter with multifrequency ...
Figure 4.26. Simulated (full-wave) RF response of electronically reconfigurable ...
Figure 4.27. Topology of electronically pattern reconfigurable antenna with inte...
Figure 4.28. Simulated (full-wave) return loss (S11) characteristics of electron...
Figure 4.29. Simulated (full-wave) H-plane radiation pattern of electronically p...
Figure 4.30. Simulated (full-wave) E-plane radiation pattern of electronically p...
Figure 4.31. Simulated (full-wave) 3D radiation pattern of electronically patter...
Figure 4.32. Simulated (full-wave) 3D radiation pattern of electronically patter...
Figure 4.33. Simulated (full-wave) surface current patterns on the antenna and p...
Figure 4.34. Simulated (full-wave) surface current patterns on the antenna and p...
Figure 4.35. Photograph of fabricated electronically pattern reconfigurable ante...
Figure 4.36. MVG Starlab® automatic 3D radiation pattern measurement system. For...
Figure 4.37. Experimental and simulated (full-wave) return loss (S11) characteri...
Figure 4.38. Experimentally obtained H-plane radiation pattern of electronically...
Figure 4.39. Experimentally obtained E-plane radiation pattern of electronically...
Figure 4.40. Experimentally obtained 3D radiation pattern of electronically patt...
Figure 4.41. Variation of H-plane gain (full-wave simulation) of electronically ...
Figure 4.42. Variation of E-plane gain (full-wave simulation) of electronically ...
Figure 4.43. Concept of flexible and electronically pattern steerable transmit a...
Appendix A
Figure A.1. Illustration of experimental setup used for observation of conductiv...
Figure A.2. Photograph of experimental setup used for observation of conductive ...
Figure A.3. Microphotographs of different phase of filament formation in copper-...
Figure A.4. Microphotographs of filament observed in forming process in copper-n...
Figure A.5. Zoomed microphotograph of filament observed in forming process in co...
List of Tables
Chapter 1
Table 1.1. Comparison of general categories of RF switching technologies
Table 1.2. Performance parameter features distinguishing requirements for memory...
Table 1.3. Targeted and desired improvements for CBRAM RF switching technology a...
Chapter 2
Table 2.1. Comparison of realized CBRAM-based CPW shunt mode RF switch with the ...
Table 2.2. Parameter values of analytically fitted electrical model, along with ...
Table 2.3. Comparison of fabricated CBRAM-based CPW shunt mode RF switches on pa...
Chapter 3
Table 3.1. Measurement of solid-state rewritable chipless RFID tags on FR-4 subs...
Table 3.2. Measurement of solid-state rewritable chipless RFID tags on paper sub...
Table 3.3. Optimized electrical equivalent model component values of rewritable ...
Table 3.4. Optimized electrical equivalent model component values of rewritable ...
Chapter 4
Table 4.1. Dimensions of electronically reconfigurable band-stop filters for geo...
Table 4.2. Parameter values of electrical equivalent model of electronically rec...
Table 4.3. Comparison of experimentally obtained and mathematical model values o...
Table 4.4. Enhancement in filter parameters as a function of number of identical...
Table 4.5. Dimensions of electronically pattern reconfigurable antenna geometry ...
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
Begin Reading
Conclusion
Appendix
References
Index
End User License Agreement
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“…ajnaana-timirandhasya jnanaanjana-salakaya caksur-unmilitam yena tasmai sri-guruve namah…”
(Excerpts from Indian philosophy in Sanskrit language)
I humbly express my deep gratitude and obeisance to all my dear teachers who opened my eyes to the wisdom of knowledge, away from the blindness of ignorance, in all phases of my life…
(Translation)
Series EditorEtienne Perret
Non-Volatile CBRAM/MIM Switching Technology for Electronically Reconfigurable Passive Microwave Devices
Theory and Methods for Application in Rewritable Chipless RFID
Jayakrishnan Methapettyparambu Purushothama
Etienne Perret
Arnaud Vena
First published 2022 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
ISTE Ltd27-37 St George’s RoadLondon SW19 4EUUKwww.iste.co.uk
John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USAwww.wiley.com
© ISTE Ltd 2022
The rights of Jayakrishnan Methapettyparambu Purushothama, Etienne Perret and Arnaud Vena to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.
Library of Congress Control Number: 2021949301
British Library Cataloguing-in-Publication Data
A CIP record for this book is available from the British Library
ISBN 978-1-78630-813-9
Preface
Science means constantly walking a tightrope between blind faith and curiosity; between expertise and creativity; between bias and openness; between experience and epiphany; between ambition and passion; and between arrogance and conviction – in short, between an old today and a new tomorrow1.
Heinrich Rohrer (Swiss Physicist)
Radio has made people smarter since its discovery in the late 1800s. Now scientists are trying to make radios smart to make life even easier. Electromagnetic propagating waves in the range of 30 kHz–300 GHz are called radio waves, and electrical equipment handling these propagations are generally called radio or radio frequency (RF) devices. Human life is dependent on RF electronics in our everyday routine. TV and radio broadcast, mobile phone communication, the Internet, microwave heating and so on are an integral part of our daily life, implicitly or explicitly.
Radio equipment can be an active device (that uses an active power source for operation), like a mobile phone or a television set, or passive equipment (that does not use an active power source for operation or data storage, but scavenges a part of an interrogating energy source), like a contactless credit card, or an anti-theft RFID label in a supermarket.
Communication, connectivity and surveillance are the major fields that utilize most of the RF electronics in this era. This may involve the connectivity between two individuals separated in two continents or between two electrical devices in a same drawing room. The advent of the Internet of things (IoT), backed by 5G communication technologies, has intensified this demand by providing connectivity to almost all our daily utility accompaniments. However, all this electrical equipment, whether active or passive, requires electrical switches, beginning with the initial need for power, and these span the entirety of the internal RF circuitry. These switches operate in different domains, ranging from electrical power switches to different relays, selectors, limit switches and RF switches.
Among these, RF switches play a key role in their domain and are unique with respect to required performances. These are used not only in wireless communications, but also in smart RF sensors and actuators of the future. RF switches allow electronic reconfiguration of device parameters such as operating frequency in a filter, radiation pattern in an antenna and so on, in order to make these devices more efficient. They are present in all communication systems and allow, in summary, signal multiplexing or regulation, so as to reconfigure, or dynamically control, the system. Today’s technological solutions for RF switching (solid-state semiconductor switches and RF micro-electromechanical-systems [MEMS]) need some improvements to meet the emerging requirements, in which the most desired innovation is non-volatile operation, i.e. operating without any energy requirements for maintaining an impedance state. Such a broadband solution, based on a flexible and low cost approach, is eagerly awaited.
Conductive bridging random access memory/metal insulator metal (CBRAM/MIM) switches are a new innovation of memory technology, which has also been identified as a potential non-volatile RF switching solution in the recent years. The primary target of this book, and the core concept of the studies presented herewith, is to introduce the idea of a new generation of electronically reconfigurable, solid-state and passive RF-microwave devices based on integrated CBRAM/MIM switching technology. We will present our work and results, focusing on the development of a new technology of low-cost non-volatile RF switches with both high performance and flexibility of implementation.
We demonstrate the basic principle of CBRAM/MIM RF switches and give proof of concept realizations of integration of this technology into passive RF and microwave devices, such as electronically rewritable chipless RFID tags, which are often referred to as the “rewritable RF barcodes of the future”, electronically pattern steerable antennas, electronically reconfigurable filters and single pole double throw (SPDT) switches on classic as well as flexible substrates. The necessary analysis and theoretical validations of these concepts are also presented with these results.
We take this work as a humble beginning for a new innovation of electronically reconfigurable and non-volatile passive RF and microwave devices, which is dedicated to the future, and nurtured from deeply within our heart, with our passion and wide-eyed dreams for the betterment of current science and technology. Our investigations and findings are organized into four chapters in this book, as described below.
In Chapter 1, a general idea of the motivation for and background of the need for a non-volatile RF switch is discussed in detail. A review of prominent RF switching technologies is presented, along with the state of the art of research in CBRAM/MIM RF switch technology. The requirement of non-volatile RF switches and the reasons for the choice of CBRAM/MIM technology for this are also explained in detail.
Chapter 2 states the real-world implementation challenges of a low-cost non-volatile RF switching technology and describes our efforts to overcome these limitations. We present in this chapter the design and optimization process of CBRAM/MIM based Coplanar waveguide (CPW) RF switches on classic as well as flexible paper substrates, using simple and low-cost methods, compatible with mass industrial production. Discussion of electrical equivalent models, time stability and other interesting features are also given in addition in this chapter. An application example of these switches in SPDT configuration is also included in this chapter.
Chapter 3 focuses on the design and development of solid-state electronically rewritable chipless RFID tags, which may be informally called “rewritable RF barcodes”. In this chapter, we describe in brief the principle of chipless RFID and present the design and realization of electronically rewritable chipless RFID tags on classic and flexible substrates. Electrical equivalent model analysis and advantages of using the proposed integrated CBRAM/MIM switches for chipless RFID applications are discussed in detail.
Chapter 4 explains the application of the proposed CBRAM/MIM RF switch technology to electronically reconfigurable filter and antenna models using simple and low-cost methods. We present the implementation of reconfigurable band-stop filters, backed by theoretical discussions and electrical model analysis. We also discuss the extension of the proposed techniques to other filter topologies and the mitigation of current limitations of realized filters in futuristic designs. Application of CBRAM/MIM RF switches for electronically reconfigurable antennas for radiation pattern steering is also presented affirmatively in this chapter. We conclude this chapter by discussing the advantage of using the proposed RF switch technology for reconfigurable antenna and filter applications.
This book also has an appendix, which contains some interesting outcomes of a control experiment for observing the filament formation in CBRAM/MIM switches.
Jayakrishnan METHAPETTYPARAMBU PURUSHOTHAMA Etienne PERRET Arnaud VENA November 2021
1
Heinrich Rohrer Quotes. (n.d.).
BrainyQuote.com
. Retrieved July 9, 2020, from
BrainyQuote.com
web site:
https://www.brainyquote.com/quotes/heinrich_rohrer_736250
.
1Motivation and Background: RF Switches and the Need for a Non-Volatile RF Switch
1.1. Introduction
In electrical engineering, a switch, in general, is a device which opens, closes or regulates a current path at a desired event, like ON or OFF. Switches are an inevitable component of all electronic systems we come across in our life. Like the presence of salt in food, most of the time we are unaware of the presence of this mighty little electrical component that plays many roles in our daily life.
Even though the basic responsibility of a switch is to control (open or close or regulate) a current path when desired, it can perform multiple functions, such as a classic vintage mechanical electrical switch, a telephone keypad, a relay in an automatic bread toaster, a switching regulator in a room heater, a capacitive or resistive touch screen of a mobile phone, an integral part of signal modulation system for communication and Internet and so on.
In a broad sense, an electrical switch is identified by the associated actuation mechanism used to close, open, or regulate the current path through it. Electrical switching action is usually associated with the following actuation mechanisms: mechanical (mechanical toggle switches), electronic (PIN diodes, field effect transistor [FET], electromechanical relays), chemical (azobenzene photoelectric switches), magnetic (reed switches), light (opto-couplers), software defined (routers), ionic bridging (conductive bridging random access memory [CBRAM]), phase change and so on. This definition, however, is a very crude explanation of available switch technologies, which are in greater abundance than could be analyzed or differentiated in a single book.
In this book, we concentrate on non-volatile (which do not require a power supply to maintain their impedance state) switches for radiofrequency (RF) and microwave frequencies using nanoionic conductive-bridging metal–insulator–metal (MIM) switch technology, generally identified as CBRAM, for low-cost RF and microwave devices. Here, we focus on overcoming one of the significant shortcomings of passive RF and microwave devices, which is non-volatile electronic reconfigurability.
In this book, we propose techniques to make possible the integration of passive non-volatile switches with passive devices that primarily work in the frequency range of a few MHz to around 10 GHz. Referring to this frequency range, we assume the freedom to address the domain of this book as “RF” or “microwave” frequencies, interchangeably. This book aims to democratize the CBRAM/MIM switching technology for passive/low-power RF and microwave devices using a simple manufacturing process, which is compatible with mass production, at an economically efficient budget.
In this chapter, we discuss and give some examples about the need for such a study, and the background information available at the start of the research. We give a brief introduction on the available RF and microwave switch technologies. Then we present the state of the art in memristive CBRAM/MIM switch technology, and explain the reasons for choice of this technology in this research. We also provide in brief an introduction to targeted RF domains, which are the point of application of the developed CBRAM/MIM RF switching solutions.
1.2. Requirements and definition of a switch at RF and microwave frequencies
Modern life is predominantly dependent on electromagnetic energy propagations in the range 3 kHz–300 GHz on the electromagnetic spectrum, which is generally referred to as RF and microwave signals (Pozar 2005). The RF and microwave spectrum includes numerous application bands such as television, radio, mobile phone, GPS, Bluetooth, Wi-Fi, satellite and so on. RF and microwave radiations are also used for a lot of extended applications such as tracking, ranging and enhanced vision (radar and radio astronomy), heating (microwave ovens and heating in nuclear fusion reactors), imaging (microwave tomography), medical applications (microwave ablation of tissues) and so on. In essence, one could say that RF and microwave frequency signals find their application anywhere from a simple domestic kitchen to outer space.
High-frequency RF and especially microwave signals have very short free space wavelengths, typically of the order of a few tens to a few centimeters. Due to high frequency and small wavelengths, standard circuit theory and electronic circuit approaches are not enough to solve and define working phenomena in this domain (Jordan and Balmain 1968; Bahl 2003; Pozar 2005; Sadiku 2007). At these frequencies, classic lumped circuit element approximations defined by standard circuit theory prove difficult to hold onto, as at RF and microwave frequencies components are often associated with a number of distributed parameter effects arising from their geometry. This is because at these frequencies the phase of a voltage and current is significantly affected by the physical size of a device due to small wavelengths. Similarly, circuit parameters, such as inductance, capacitance and associated dielectric properties, are significant for circuit element sizes comparable to wavelengths. At these wavelengths and frequencies, electromagnetic field theory and broadly defined circuit theory, both described by Maxwell’s equations, are used for the analysis (Jordan and Balmain 1968; Bahl 2003; Pozar 2005; Sadiku 2007).
Similar to standard electronic circuits, switches are an integral and also inevitable part of RF and microwave circuits. However, some special care should be taken and some requirements should be satisfied for the design, development and applications of switches in this field. This is with respect to the previous explanations.
The performance and behavioral features desired for RF and microwave switches are not much different from those expected for any devices or circuit at these frequencies (Breed 2010). The most relevant of these requirements or performance factors are briefed as follows:
– bandwidth of operation of the switch;
– ON and OFF state insertion loss and isolation at frequencies of interest;
– switching speed;
– operating lifetime (number of switching cycles and reliability);
– figure of merit (product of OFF state capacitance and ON state impedance of the switch, typically expressed in THz);
– operating voltage and power consumption;
– power handling, stability and linearity;
– temperature and environmental dependence;
– isolation of biasing path from RF signal path;
– cross-talk and radiation isolation (isolation to other components in the circuitry).
These requirements vary according to a desired application, and are seldom obtained altogether in a single technology, but are a compromise defined with respect to a certain tradeoff, taking into account factors such as desired performance, accuracy requirements, cost, available physical space and so on.
This section and eventually this chapter chalks a boundary, helping our readers to understand and assess the outcome of the experimental results and associated discussions on CBRAM-based RF switching solutions presented herewith.
1.3. Review of RF and microwave switching technologies
A handful of switching technologies are available for RF and microwave switching, most of them with a unique distinctive feature. Some of the common technologies include PIN junction diode switches (Keysight Technologies 2019), FET switches (Keysight Technologies 2017a), hybrid switches like microwave monolithic integrated circuits (MMIC) (Mizutani and Takayama 2000; Keysight Technologies 2014), electromechanical RF switches like micro-electromechanical-systems (MEMS) (Analog Devices 2018) and so on.
New innovations such as memristive switches, including phase change memory (PCM) (Wang et al. 2014) or CBRAM (Pi et al. 2015), and engineered material switches, such as monolayer grapheme-based switches (Li and Cui 2015; Moldovan et al. 2015; Ma et al. 2016; Pan et al. 2017), are also in a budding stage to redefine the future of RF switching.
In this chapter, we discuss only the significant switching technologies of the above list. We also outline the state of the art of the topic in focus in this book, which is the memristive CBRAM/MIM switch technology. Here, we try to differentiate and compare this technology with the former counterparts.
Classically, RF and microwave switches could be broadly grouped into three main categories as follows:
1) electromechanical switches;
2) solid-state (semiconductor-based) switches;
3) memristive switches.
Electromechanical switches are similar to electrically actuated mechanical switches such as relays and were succeeded by more efficient technologies such as MEMS. Solid-state switches generally work on the basis of regulated electron flow through semiconductor or engineered materials, such as PIN diodes, FETs and hybrid semiconductor switches.
Table 1.1.Comparison of general categories of RF switching technologies
Technology (Right) Parameters (Down)
Solid-state semiconductors
MEMS
Memristive switches
ON state impedance
~1 Ω
~0.5–2 Ω
~2–10 Ω
Lower frequency limit
DC to a few kHz
DC
DC
Upper frequency limit
>100 GHz
>1 THz
>40 GHz
Switching time
10–100 ns
1–300 µs
1–10 µs
Figure of merit (THz)
1–4
10–300
0.015–38
Non-volatility
No
No
Yes
Fabrication complexity
High
Very high
High, low
*
Commercial availability
Yes
Yes
No
Cost
Low
High
No commercial products
*
High for classic fabrication techniques (Nessel and Lee 2011; Pi
et al.
2015) and low for fabrication with polymer ion-conductors (Perret
et al.
2015; Jian
et al.
2017).
Here, we take the privilege of introducing a third and emerging category called “memristive switches”, which is the focus topic of this book. We present this topic as a separate category for detailed discussion to highlight its relevance and unique characteristics.
