Slow-wave Microwave and mm-wave Passive Circuits E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 385

Veröffentlichungsjahr: 2024

Beschreibung

Comprehensive resource presenting the fundamentals and state of the art concepts, design examples, relevant components, and technology

Slow-wave Microwave and mm-wave Passive Circuits presents the fundamentals and state of the art concepts, design examples, relevant components, and technology of the subject, plus examples of circuit layout optimization using slow-wave circuits. Recent advances in aspects of the slow-wave concept are covered, with potential applications including automotive radars, medical and security applications, and 5G and future 6G for very high-speed communications.

The text considers a variety of slow-wave structures and associated concepts which are useful for circuit design, each structure electrically modeled with clear illustration.

The highly qualified authors show that the use of the slow-wave concept can, in some cases, improve the performance of passive circuits. The techniques proposed make it possible to reduce the size and/or the performance of the circuits, with a beneficial cost-saving effect on semiconductor materials. Concepts are applied to several technologies, namely CMOS, PCB (Printed Circuit Board) and nanowires.

Sample topics covered include:

• Concepts of energy storage with examples of slow-wave CPW (S-CPW), slow-wave SIW (SW-SIW), and slow-wave microstrip (S-MS),
• Transmission line topology and application in integrated technologies (CMOS), including possibilities offered by the BEOL (Back-End-Of-Line),
• Effect of the geometrical dimensions on the transmission line parameters (Z_c, α, ε_reff, and Q) and comparisons between conventional CPW and CPS, and slow-wave CPW and CPS,
• Performance of slow-wave coupled lines and comparison with conventional microstrip coupled lines.

Slow-wave Microwave and mm-wave Passive Circuits is a highly useful resource for graduate students (best complemented with a basic book on microwaves), engineers, and researchers. The text is also valuable for physicists wishing to implement comparable techniques in optics or mechanics.

Leseprobe

Slow-Wave Microwave and mm-Wave Passive Circuits

Edited by

Philippe Ferrari

TIMA, Université Grenoble Alpes, CNRS, Grenoble INP, Grenoble, France

Anne-Laure Franc

LAPLACE, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France

Marc Margalef-Rovira

STMicroelectronics, RFC HDC, Crolles, France

Gustavo P. Rehder

University of São Paulo, São Paulo, Brazil

Ariana Lacorte Caniato Serrano

University of São Paulo, São Paulo, Brazil

This edition first published 2025© 2025 John Wiley & Sons Ltd.

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The right of Philippe Ferrari, Anne-Laure Franc, Marc Margalef-Rovira, Gustavo P. Rehder, and Ariana Lacorte Caniato Serrano to be identified as the authors of the editorial material in this work has been asserted in accordance with law.

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List of Contributors

Matthieu BertrandIMEP-LAHC, CNRS, Grenoble INPUniversité Grenoble Alpes, Grenoble France

Jordan CorsiTIMA, Université Grenoble Alpes, CNRSGrenoble INP, Grenoble, France

Philippe FerrariTIMA, Université Grenoble Alpes, CNRSGrenoble INP, Grenoble, France

Anne-Laure FrancLAPLACE, Université de Toulouse, CNRSINPT, UPS, Toulouse, France

Leonardo GomesTIMA, Université Grenoble AlpesGrenoble, France

and

Polytechnic School, University of SãoPaulo, São Paulo, Brazil

and

STMicroelectronics, RFC HDC, CrollesFrance

Hamza IssaFaculty of Engineering, Beirut ArabUniversity, Beirut, Lebanon

Marc Margalef-RoviraSTMicroelectronics, RFC HDC, CrollesFrance

Emmanuel PistonoTIMA, Université Grenoble Alpes, CNRSGrenoble INP, Grenoble, France

Gustavo P. RehderPolytechnic School, University of São Paulo, SãoPaulo, Brazil

Abdelhalim SaadiNXP, R&D HW RFP, Toulouse,France

Ariana Lacorte Caniato SerranoPolytechnic School, University of SãoPaulo, São Paulo, Brazil

Preface

Français

Écrire un livre sur les lignes à ondes lentes peut sembler une aventure périlleuse, car il y a mille et une manière de ralentir une onde électromagnétique. L’approche peut être basée sur l’utilisation de matériaux diélectrique ou magnétique, sur l’utilisation de composants tels des inductances ou des condensateurs, ou encore sur l’utilisation de méthodes de guidage particulières permettant de perturber les champs magnétique ou électrique. Toutes ces méthodes ont été étudiées au sein de la littérature scientifique.

Nombre d’entre elles ne sont pas abordées au sein de ce livre, en particulier deux méthodes très bien illustrées, à savoir l’utilisation de défauts de plan de masse et l’utilisation de composants localisés de type inductance, et surtout condensateur. L’utilisation de matériaux magnétique à forte perméabilité ou de matériaux diélectrique à forte constante diélectrique est également bien documentée au sein de la littérature, mais leur mise en oeuvre pose des problèmes, soit en termes de pertes, soit en termes de technologie, soit en termes de limitations électriques, en particulier par le fait qu’il est alors compliqué de réaliser des lignes de transmission possédant une impédance caractéristique au moins égale à 50 Ohms.

Après plus de quinze années de travaux de recherche au sein de nos équipes, nous, les cinq éditeurs de ce livre, avons décidé qu’il était temps de regrouper l’ensemble de nos travaux au sein d’un livre, afin de donner aux futurs lecteurs une vue globale de l’approche que nous avons développée. Cette approche consiste à construire des solutions de guidage des ondes en modifiant la topologie du champ électrique. Chacun aurait bien sûr le souhait de pouvoir également jouer avec le champ magnétique, mais la nature, qui souvent nous délivre des objets symétriques, n’a pas choisi la symétrie pour le comportement des champs électrique et magnétique. L’absence de charges magnétiques implique une distinction fondamentale des champs. Ainsi il s’avère très simple de configurer un champ électrique, en lui présentant les charges vers lesquelles il va naturellement se diriger. Le champ magnétique est plus sauvage, il tourne sur lui-même et ne peut être attiré, sauf par des matériaux de forte perméabilité, qui peuvent le dévier.

Sur la base de ce principe de configuration du champ électrique, nous présentons au sein de ce livre trois types de lignes à ondes lentes, (i) les lignes de type coplanaires, coplanar waveguide ou coplanar stripline, qui constituent le premier type de lignes à ondes lentes véritablement utilisées comme telles avec une très bonne efficacité en technologie intégrée de type CMOS, et mises en oeuvre pour la première fois par l’équipe de John Long, alors à TU Delft, puis (ii) les lignes microruban, et (iii) les guides d’ondes SIW. Sur la base de ces trois types de lignes, nous décrivons un grand nombre de circuits dont les performances et/ou les dimensions ont pu être améliorées grâce à l’utilisation du concept d’onde lentes.

In fine, nous espérons que les lecteurs prendront beaucoup de plaisir à parcourir ce livre que nous avons tous écrit avec grand plaisir.

English

Writing a book on slow-wave transmission lines may seem like a perilous adventure, as there are a thousand and one ways to slow down an electromagnetic wave. The approach is based on the use of dielectric or magnetic materials, the utilization of components such as inductors or capacitors, or even the application of specific guiding methods that disrupt the magnetic or electric fields. All of these methods have been studied within the scientific literature.

All these methods will not be addressed in this book, particularly only two methods are well illustrated: the use of defected ground planes and the use of lumped components such as inductors, especially capacitors. The use of high-permeability magnetic materials or high-dielectric constant dielectric materials is also well documented in the literature, but their implementation poses problems, either in terms of losses, technology, or electrical limitations. This is especially true because it becomes complicated to design transmission lines with a characteristic impedance of at least 50 Ω in such cases.

After more than 15 years of research within our teams, we, the five editors of this book, have decided that it is time to consolidate all of our work into a book to provide future readers with a comprehensive view of the approach we have developed. This approach involves constructing wave-guiding solutions by modifying the topology of the electric field. Everyone, of course, wishes to also play with the magnetic field, but nature, which often delivers symmetrical objects, has not chosen symmetry for the behavior of the electric and magnetic fields. The absence of magnetic charges implies a fundamental distinction in the fields. Thus, it turns out to be straightforward to configure an electric field by presenting charges toward which it will naturally move. The magnetic field is more untamed; it rotates on itself and cannot be attracted, except by materials with high permeability that can deflect it.

Based on this principle of electric field configuration, we present in this book three types of slow-wave structures: (i) coplanar lines (coplanar waveguide or coplanar stripline), which constitute the first type of slow-wave transmission lines genuinely used as such with very good efficiency in CMOS integrated technology, and first implemented by John Long’s team at TU Delft, (ii) microstrip lines, and then (iii) substrate integrated waveguides (SIW). Building upon these three types of lines, we describe a large number of circuits whose performances and dimensions have been enhanced using the slow-wave concept.

In conclusion, we hope that readers will thoroughly enjoy reading this book, which we have all written with great pleasure.

Acronyms

3D

Three-Dimensional

AAO

Anodic Aluminum Oxide

AF-S-MS

Air-Filled Suspended S-MS

BEOL

Back-End-Of-Line

BiCMOS

Bipolar Complementary Metal-Oxide-Semiconductor

CAD

Computer-Aided Design

CCP

Crossed-Coupled Pair

CMOS

Complementary Metal-Oxide-Semiconductor

CPS

CoPlanar Stripline

CPW

CoPlanar Waveguide

DBR

Dual Behavior Resonator

DC

Direct Current

EM

Electromagnetic

FOM

Figure of Merit

FOMT

Figure of Merit with tuning range

FTR

Frequency Tuning Range

FWDC

Forward-Wave Directional Coupler

GSG

Ground Signal Ground

GSGSG

Ground Signal Ground Signal Ground

HR-SOI

High Resistivity Substrate On Insulator

IL

Insertion loss

LC

Liquid Crystals

LCP

Liquid Crystal Polymer

LNA

Low-Noise Amplifier

LRRM

Load Reflect Reflect Match

LTCC

Low Temperature Co-fired Ceramics

MEMS

MicroElectroMechanical System

mm-waves

Millimeter-waves

MOS

Metal-Oxide-Semiconductor

MOSFET

Metal Oxide Semiconductor Field-Effect Transistor

PA

Power Amplifier

PCB

Printed Circuit Board

PDK

Public Design Kit

QS

Quasi-Static

RF

RadioFrequency

RFIC

RadioFrequency Integrated Circuit

RL

Return Loss

SOI

Silicon on Insulator

S-MS

Slow-Wave Microstrip

SW

Slow-Wave

SWF

Slow-Wave Factor

TRL

Thru Reflect Line

VCO

Voltage-Controlled Oscillator

VNA

Vector Network Analyzer

1Background Theory and Concepts

Philippe Ferrari1, Marc Margalef-Rovira2, and Gustavo P. Rehder3

1TIMA, Université Grenoble Alpes, CNRS, Grenoble INP, Grenoble, France

2STMicroelectronics, RFC HDC, Crolles, France

3Polytechnic School, University of São Paulo, São Paulo, Brazil

The objective of this introductory chapter is to draw up a brief history of slow-wave structures in Section 1.1, then to define the concept of slow-wave propagation from a theoretical point of view in Section 1.2, next to briefly present the three slow-wave transmission lines (in Section 1.3) presented in detail within the following chapters, namely slow-wave coplanar waveguides (S-CPWs, Chapter 2), slow-wave coplanar striplines (S-CPS, Chapter 2), slow-wave microstrip (S-MS, Chapter 3), slow-wave substrate integrated waveguides (SW-SIW, Chapter 4), and finally, in Section 1.4, to highlight some advantages of modern slow-wave transmission lines, which is a big part of the motivation for this book.

1.1 Historical Background

During the second half of the 20th century, technological advancements had greatly impacted modern society, with telecommunication networks being one of the most notable. With numerous scientific and technological breakthroughs, these networks have become more complex and efficient. This has led the consumer electronics market to become economically significant, with the development of new services and activities driven by the increasing demand for high-definition multimedia applications, secure data transmission, wearables, etc. To provide the necessary bandwidths and subsequent data rates for these applications, the next generation of wireless communications is oriented toward higher frequencies, especially the millimeter wave (mm-wave) bands. However, this presents new challenges, such as the need for wireless transceiver circuits that can operate at high frequencies with reasonable efficiencies, relying on low-cost technologies and compact solutions. Slow-wave structures can be a solution for the design of compact circuits.

The concept of slow-wave structures emerged in the early 1940s, for their capability to establish efficient interaction with electron beams. More precisely, it started in the context of radar applications where these interactions were used to amplify RF waves. The amplification was based on transferring kinetic energy from electrons to a propagating wave. Based on this principle, the first slow-wave structure was called “klystron,” a high-frequency vacuum tube invented in 1937 by W. Hansen and the Varian brothers (Varian & Varian, 1939), as illustrated in Fig. 1.1(a). In these amplifiers, the slow-wave propagation was achieved by cascading resonant cavities, which resulted in narrowband operation (Wu, 1999). In these structures, the slow-wave propagation was necessary because the interaction requires close velocities between the wave and the electrons, which move in vacuum at a lower velocity than the light. This interaction was further enhanced by R. Kompfner, who realized, in 1943, a broadband amplifier based on a nonresonant helix structure called “traveling-wave tube” (TWT; Kompfner, 1947), illustrated in Fig. 1.1(b). Improved versions of these devices are still in use for radar, satellite communications, television broadcasting, and particle accelerators. Oscillators have also been developed based on the same principles.

Figure 1.1 (a) First commercial klystron.

Source: Henney 1940/with permission of WorldRadioHistory;

(b) Traveling-wave tube principle of operation.

Source: Adapted from Kompfner (1947).

During the 1960s, the development of integrated microwave circuits provided a good opportunity to develop layered structures with potential slow-wave propagation. This concept was demonstrated for the first time in 1969 for a metal–insulator–semiconductor microstrip structure (Hasegawa et al., 1971) on silicon. It was followed by several topologies, including the Schottky contact transmission line (Jager, 1976). Thanks to an external bias, this last structure was used to create a variable slow-wave effect (Jaffe, 1972). As explained in (Wu, 1999), planar periodic structures gained attention in the early 1970s for the development of wide-band coupled microstrip lines (Podell, 1970). Since then, the research on planar periodic and layered structures has continued until today. In the meantime, slow-wave planar structures have also been used for miniaturization purpose. In microwave passive circuit design, specific functions such as filters, antennas, and couplers can be realized by the combination of physical phenomena such as interference, resonance, and couplings. These phenomena are very often dependent on wavelengths, so that specific properties can be obtained for given dimensions. It also means that, in general, these passive circuits occupy much larger areas than the active ones, which are made of increasingly smaller transistors. For example, a floating straight transmission line has intrinsic resonance frequencies that are directly related to the ratio of the propagation velocity and its physical length. Therefore, for a given frequency, a miniaturized structure can be obtained if the velocity is accordingly reduced. Obviously, the challenge lies in the effort to make such slow-wave structures as efficient in terms of dissipation as the original ones. In printed-circuit-board technology, a high number of topologies have been developed in the recent years, some of them are illustrated in Fig. 1.2. Figure 1.2(a) shows spoof surface plasmon-based transmission lines, for compact designs, reduced attenuation and limited cross-talk (Kianinejad et al., 2015). Compact couplers, such as the “rat-race,” are illustrated in Fig. 1.2(b). The compactness was achieved by using a high slow-wave factor (SWF) microstrip structure (Chang & Chang, 2012). In Fig. 1.2(c), a filter based on six slow-wave resonators is also shown (Shi et al., 2010). One could also mention the use of defected ground (Kim & Lee, 2006) and electromagnetic band-gap (Zhurbenko et al., 2006), which often exhibit slow-wave propagation.

Figure 1.2 (a) Spoof surface plasmon-based slow-wave transmission lines.

Source: Kianinejad et al. (2015)/with permission of IEEE;

(b) Rat-race coupler.

Source: Wei-Shin Chang et al. 2012/with permission of IEEE;

(c) Six-resonator low-pass filter based on slow-wave resonators.

Source: Shi et al. (2010)/with permission of IEEE.

Concerning integrated technologies, the design of compact and low-loss passive circuits is a real challenge. It is especially true for the newly addressed mm-wave bands, in which parasitic couplings are more and more limiting and where the high conduction losses result in poor quality factors. In this context, slow-wave structures do not only provide miniaturized circuits but may also lead to higher quality factors (Chee et al., 2006; Cheung & Long, 2006; Franc et al., 2013). This is the case of the S-CPW, whose geometry prevents conduction losses in the semiconductor by shielding the electric field (see Fig. 1.3(a)). Meander lines were also used to realize compact couplers in silicon-based integrated passive device (IPD) technologies (Tseng & Chen, 2016), as shown in Fig. 1.3(b). A band-pass filter using a slow-wave microstrip topology was presented in (Evans et al., 2012), it is illustrated in Fig. 1.3(c).

1.2 The Slow-Wave Concept

In this section, a general theoretical approach explaining the concept of slow-wave propagation is presented. It is based on the magnetic and electric energies that are stored in a waveguide (Bertrand et al., 2020).

A general uniform waveguide topology is illustrated in Fig. 1.4.

The cross section could contain either different metallic conductors, magnetic, or dielectric materials. A wave propagating inside such a waveguide is characterized by its phase constant β and angular frequency ω. By definition, its phase velocity vp is the velocity at which the phase of the wave travels in space, and is defined as (1.1).

(1.1)

Figure 1.3 (a) Slow-wave coplanar waveguide topology.

Source: Franc et al. (2013)/with permission of IEEE;

(b) Slow-wave coupler in silicon-based IPD technology.

Source: Tseng et al. 2016/with permission of IEEE;

(c) Miniaturized slow-wave microstrip filter in 65-nm CMOS technology.

Source: Evans et al. (2012)/with permission of The Institution of Engineering and Technology.

It can be seen as the velocity at which an observer should travel along the waveguide in order to keep in state with this wave. A second velocity is called group velocity, vg, and it is the velocity at which the overall shape of the waves’ amplitudes – or modulation – travels through space. This velocity is also often interpreted as the velocity at which the energy or information propagates; it is given by (1.2).

(1.2)

By definition, for a non-dispersive propagating mode such as the lossless TEM (Transverse Electric Magnetic) mode, the phase velocity does not depend on frequency, which implies that the phase constant β is a linear function of ω. In that case, it follows that vp = vg. However, if this velocity does vary, the group velocity differs from the phase velocity. The phase velocity (and therefore the group velocity) in a specific material is fixed by its permittivity ε and permeability μ, in particular . For a guided wave, however, dispersion occurs so that phase and group velocities can greatly differ from the free-space value. As explained in (Wu, 1999), in a closed uniform waveguide, waves propagate at velocities greater than the light velocity; they are commonly called “fast-waves.” This is equivalent to say that the guided wavelength λ is greater than the free-space wavelength. On the contrary, some structures can exhibit lower velocities compared to free-space propagation. These waves are therefore called “slow-waves” and are characterized by smaller guided wavelengths. The velocity reduction can be obtained by specific spatial variations of material properties in the transverse section, as shown in Fig. 1.4. Another method relies on the introduction of periodicity in the propagation direction, either in material properties or in the boundary conditions. In order to quantify the velocity reduction, a common definition of a so-called swf is adopted (Wu, 1999). This factor is defined as the ratio between the free-space velocity in vacuum c0 and actual phase velocity in the considered waveguide vp (see (1.3)). This factor is also called the effective refractive index, as defined in optics.

Figure 1.4 General form of a uniform waveguide.

(1.3)

It can also be expressed as the ratio of free-space and guided wavelengths λ0 and λ, or phase constants β0 and β, respectively. Usually, an effective relative permittivity εreff is introduced, integrating both magnetic and electrical effects into one single parameter (as in Wu, 1999). In this definition, εreff contains the contribution of material properties (εr, μr), as well as any additional slow-wave mechanism.

From the definition given previously, a slow-wave structure is characterized by a swf greater than one. However, based on this definition, most existing waveguides (TEM or not) are slow-wave structures because they contain dielectric materials with εr > 1. For convenience, a second definition of SWF may be used to remove this ambiguity. It is defined as the ratio between the phase velocity in a given wave-guiding structure taking the material properties into account, and vp, the one achieved through additional geometry and material modifications (see (1.4)).

(1.4)

Besides, if the reference waveguide supports a TEM mode so that its phase velocity can be expressed as , then the following relation between the two definitions can be derived:

(1.5)

As a result, the effective relative permittivity becomes:

(1.6)

The scientific literature related to the design of slow-wave waveguides and passive components regularly claims that the slow-wave propagation is conditioned by a spatial separation of electric and magnetic energies (Wu, 2005). This separation requirement is generally mentioned along with the necessity to increase stored energy in the structure (Jin et al., 2016; Niembro-Martin et al., 2014). Naturally, the impact of the field distribution modification within slow-wave structures is usually described in terms of increased capacitance or inductance using distributed L-C models (Bastida & Donzelli, 1979).

A general explanation of the relationship between spatial separation and reduced propagation velocity without recurring to circuit approximate modeling is provided further. One can distinguish between two approaches in generating slow-wave propagation. The first one relies on using specific material arrangement in the transverse section of a longitudinally uniform waveguide. These materials may include dielectrics with different dielectric constants or more complex materials, such as semi-conductors, for instance. The second approach relies on the introduction of longitudinally periodic variations of boundary conditions or material properties. It is worth noting that for lossless periodic waveguides, allowing propagation in specific frequency pass-band, stored electric and magnetic energies obey the two theorems as follows (Collin, 1990; Watkins, 1958):

Theorem 1.1 The time-average stored electrical energy per period is equal to the time-average stored magnetic energy per period in the pass-band.

Theorem 1.2 The time-average power flow in the pass-bands is equal to the group velocity times the time-average stored electrical and magnetic energy per period divided by the period.

These two theorems can be expressed by equations (1.7) and (1.8), respectively, using the field complex vectors E and H.

(1.7)

(1.8)

where V is the volume of an s-periodic waveguide period along z coordinate (propagation direction), St(z) its transverse section, and vg the group velocity. We also denote the stored electric and magnetic energies in a period as We and Wm, respectively. It is important to note that in the case of uniform waveguides, these two theorems also apply, as the period s can be fixed to any real value. From these two theorems, it naturally follows that for two waveguides, namely 1 and 2, having identical periods and carrying the same amount of power, the energy stored and the group velocities are closely related (1.9).

(1.9)

In other words, the ratio of group velocities for propagation in the aforementioned waveguides is directly given by the ratios of stored energies, see (1.10).

(1.10)

Now, in the case of a low dispersion propagation scheme, this ratio can be expressed as the ratio of phase velocities, as shown in (1.11).

(1.11)

Most slow-wave waveguides in the literature consist of modified versions of well-known wave-guiding topologies, such as closed circular or rectangular waveguides or planar transmission lines (coplanar, microstrip). Therefore, it is usually convenient to use such an existing waveguide as point of reference when dealing with the performance of a specific slow-wave implementation.

As a conclusion, the phase velocity reduction in slow-wave structures can be related to energy considerations, if both low dispersion and low losses are assumed. In this case, the reduction in velocity as compared to a reference waveguide carrying the same amount of power is approximated by the equation (1.12).

(1.12)

where We and Wm are the time-averaged energies stored in a period of the slow-wave waveguide (or arbitrary section if uniform), while and correspond to the chosen reference waveguide.

1.3 Modern Slow-Wave Transmission Lines Brief Description

As highlighted in Section 1.1, the concept of slow-wave transmission lines is not new in the 21st century, but the development of slow-wave transmission lines making it possible to produce RF and mm-wave circuits with high efficiency is relatively new (early 2000s for the first demonstrations). It is in this sense that we use the word “modern” to qualify the slow-wave transmission lines presented in this book.

1.3.1 Slow-Wave Coplanar Waveguide

As shown in Fig. 1.5, the S-CPW is simply a CPW under which a floating shield has been inserted. The electrically floating shield consists of metallic ribbons placed in a perpendicular configuration, as compared to the direction of propagation. The electrical and magnetic field lines for the central conductor are drawn in Fig. 1.5. As it will be explained in detail in Chapter 2, the magnetic field, as compared to a classical CPW, is almost unperturbed by the floating shield while the electric field is captured by it.

From a circuit point of view, this leads to an increase in the CPW linear capacitance Clin and, hence, a decrease in the phase velocity vp, which is given by equation (1.13):

(1.13)

with Llin