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Analysis of Slow-Wave Coplanar Waveguide for Monolithic Integrated Circuits
Abstract
The slow-wave characteristics of an MIS coplanar waveguide are analyzed using two diferent full-wave methods: mode-matching and spectral-domain technique. The theoretical results obtained with them and the experimental values are in good agreement. Several important features of the MIS coplanar waveguide are presented along with some design criteria.
... Following the first reported MIS coplanar slow-wave structure (MIS-CSWS) on GaAs substrate [4], various approaches were proposed to achieve low-loss propagation inside the MIS coplanar transmission lines [5]- [8]. Numerous works were also dedicated to the analysis of MIS-CSWS, either numerically [7], [9], [10] or analytically [11]- [16]. Among these analysis techniques, full-wave methods are unsuitable for the design of MIS-CSWS because of their high computational complexity and limited physical insight. ...
... Among these analysis techniques, full-wave methods are unsuitable for the design of MIS-CSWS because of their high computational complexity and limited physical insight. Meanwhile, the mode-matching method [9], [10] and the spectral domain method [10] are inadequate as they assume a perfect conductor in the development of numerical solutions, and hence conductor losses are systematically ignored. Some closed-form analytical models were reported in [6] and [11]- [16], but none of the above modeling techniques is suitable to model both thin-film and thick-film MIS-CSWS [6] with acceptable accuracy. ...
... Among these analysis techniques, full-wave methods are unsuitable for the design of MIS-CSWS because of their high computational complexity and limited physical insight. Meanwhile, the mode-matching method [9], [10] and the spectral domain method [10] are inadequate as they assume a perfect conductor in the development of numerical solutions, and hence conductor losses are systematically ignored. Some closed-form analytical models were reported in [6] and [11]- [16], but none of the above modeling techniques is suitable to model both thin-film and thick-film MIS-CSWS [6] with acceptable accuracy. ...
This paper presents a thermo-tunable metal-insulator-vanadium dioxide (MIV) coplanar waveguide structure (CPW). An analytical quasi-TEM model is used to thoroughly study the structural and material-dependent characteristic parameters of the device, while the temperature-dependent broadband permittivity and conductivity of the deposited vanadium dioxide (VO₂) thin film at microwave frequencies are experimentally extracted. The designed thermo-tunable MIV-CPW, focused on its slow-wave properties, shows a drastic increase in slow-wave factor when the temperature of the VO₂ thin film is increased over its transition temperature. This phase change allows converting this composite structure into the metal-insulator-semiconductor coplanar slow-wave structure. This demonstrates the potential of such MIV-CPW for the design of tunable and reconfigurable integrated microwave passive components with a significantly reduced size.
... However, this assumption is not true for modern high-speed VLSI. Figure 1 gives the performance enhancement of interconnects as the technology advances [22]. includes the spectral domain analysis (SDA) method [15], the method of lines (MOL) [24], the transmission line matrix (TLM) method [25], the finite-difference timedomain (FDTD) method [8], the finite element method (FEM) [5], and the boundary element method (BEM) [26] etc.. A short introduction of these full-wave analysis methods can be found in the next two sections. ...
... According to Yee [32], E field is always calculated on time-step n,n+1, etc; H field is always calculated on time-step n+1/2, n+3/2, etc. In (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), the magnetic field terms on the right hand side are n H 's, which are not stored in computer memory. ...
... We will present the conventional ADI-FDTD method in this section. The We start by deriving the ADI-FDTD from the FDTD method (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). In FDTD method, we compute the field marching from time step n to n+1 in an explicit way. ...
... The FGC line shown in Figure 1 may be thought of as a Metal-Insulator-Semiconductor (MIS) structure that may support three modes of propagation (skin effect mode, a dielectric quasi-TEM mode, and a slow-wave mode), and prior work on MIS coplanar waveguides has explored this with the goal of developing slow wave structures for circuits size reduction [5][6][7]. However, the slow-wave structures were built on thin insulators deposited over a thin, highly doped semiconductor la yer that is grown on an insulating material [5,6]. ...
... The FGC line shown in Figure 1 may be thought of as a Metal-Insulator-Semiconductor (MIS) structure that may support three modes of propagation (skin effect mode, a dielectric quasi-TEM mode, and a slow-wave mode), and prior work on MIS coplanar waveguides has explored this with the goal of developing slow wave structures for circuits size reduction [5][6][7]. However, the slow-wave structures were built on thin insulators deposited over a thin, highly doped semiconductor la yer that is grown on an insulating material [5,6]. Because the insulating layer is thin (less than 1 µm), the fields interact strongly with the semiconductor layer and the attenuation is reported to be greater than 10 dB/cm [6,7]. ...
... However, the slow-wave structures were built on thin insulators deposited over a thin, highly doped semiconductor la yer that is grown on an insulating material [5,6]. Because the insulating layer is thin (less than 1 µm), the fields interact strongly with the semiconductor layer and the attenuation is reported to be greater than 10 dB/cm [6,7]. Thus, while interesting and useful for some purposes, the attenuation is too high for most Si RFICs. ...
Measured propagation characteristics of Finite Ground Coplanar (FGC) waveguide on silicon substrates with resistivities spanning 3 orders of magnitude (0.1 to 15.6 Ohm cm) and a 20 ¿m thick polyimide interface layer are presented as a function of the FGC geometry. Results show that there is an optimum FGC geometry for minimum loss, and silicon with a resistivity of 0.1 Ohm cm has greater loss than substrates with higher and lower resistivity. Lastly, substrates with a resistivity of 10 Ohm cm or greater have acceptable loss characteristics.
... The electric and magnetic field distributions E and B around the CPW can be computed using full-wave analysis, which also provides information regarding the frequency dependence of the phase velocity and the characteristic impedance. Several techniques has been developed including the spectral domain method [132,133,134,135,136], mode-matching technique [137], the integral equation approach [138], the method of moments [139], and the finite difference time domain technique [140]. These techniques are particularly important at higher frequencies (ω mw > 10 GHz). ...
... {t 11 , t 12 , t 13 , t 14 } ≃ {1.0196, 5.9525, −0.6561, −1.5298} (134) which corresponds to the currents setting : ...
In this thesis, we report the theoretical study of an atom interferometer using thermal (i.e. non condensed) atoms trapped on a chip, with reduced mean-field effects. To keep an adequate level of coherence, a high level of symmetry between the arms of such an interferometer is required. To achieve this goal, we describe an experimental protocol based on microwave near-fields created by two coplanar waveguides carrying currents oscillating at different frequencies. This method enables the creation of two symmetrical microwave potentials that depend on the atomic internal state, and allows a state-selective symmetrical splitting of the atoms. We mainly consider two symmetrical configurations to separate the atoms either along the longitudinal axis or along the transverse axis of the static magnetic trap. In the case of a transverse splitting of the atoms, we discuss the advantages of using a custom microtrap that has the same field structure as a standard macroscopic Ioffe Pritchard trap, and we propose a practical design for such a microtrap. In the case of an axial splitting of the atoms, we study some physical factors limiting the ultimate performances of this interferometer such as: the dissymmetry of the microwave potentials, the effect of the fluctuations of static and microwave fields and the stability of the interferometer gravitational signal. We derive a simplified one-dimensional harmonic model to describe the interferometer contrast decay. Finally, we consider the possibility of non-adiabatic atomic splitting and recombination without vibrational heating by designing appropriate trajectories of the trapping-potentials based on the theory of dynamical invariants.
... Due to this partitioning of energy storage, the propagation velocity is much smaller than the permittivity of the surrounding media suggests. Another approach to create a slow-wave substrate is to fabricate a cross-tie periodic pattern below the CPW lines, which consists of periodically doped regions within the substrate [54], [55]. Analysis shows that the basic structure consists of two different transmission line segments with different characteristic impedances and phase constants. ...
... In [17], [21], [56], metal strips are placed on a lower metal layer in the fabrication technology. Similar to the cross-tie periodic pattern described in [54] and [55], the metal strips are placed below the CPW traces to produce the slow-wave substrate. This is illustrated in Figure 2.12. ...
... In 1976, Dieter et al. proposed a SW-TL based on Schottky microstrip line, which establishes a Schottky barrier layer near the conductor of the transmission signal with frequency-dependent characteristics to achieve slow-wave effect [7] . In 1977, Hasegawa et al. designed a coplanar stripline SW-TL based on MIS and Schottky barrier using GaAs dielectric plate, and analyzed the electromagnetic characteristics of the transmission line [8] . In 1983, Yoshiro et al. designed MIS SW-TL by controlling the doping medium. ...
In this paper, the research status and implementation methods of slow wave transmission lines are analyzed. Slow wave transmission lines are distinguished from other planar artificial transmission lines by the positive and negative values of equivalent permittivity and permeability. On this basis, the realization method is summarized through the analysis of equivalent dielectric constant and permeability. The methods of multi-layer dielectrics, periodically loaded capacitors (inductors or branches), cascaded cells and defective ground structures are summarized to increase the value of ε and μ, so as to reduce the phase velocity of electromagnetic wave and realize slow wave transmission line. It provides a reference for the design and application of slow wave transmission lines.
... Cette géométrie, imposée par la configuration MZ, est celle d'une ligne à deux rubans couplés. La diminution simultanée de l'écartement entre les rubans et de leur largeur a pour effet d'abaisser nm cff [8] [9]. Le but est d'optimiser ces dimensions pour que la variation de la tension de polarisation, entre OV et une valeur négative modérée, entraîne une excursion de nm eff de part et d'autre de la valeur de no eff. ...
This paper addresses a new type of travelling wave electrooptic modulators. The proposed modulator is tuned by an external variable voltage. By this method one may match the microwave index to the optical one. The consequence is a significant enhancement of the bandwidth modulation.
... The E field distributions in the slot line and the coupled slot line have been shown in figures 2(a) and (b), respectively, along the x-and z-directions. The basis functions chosen for the analysis are as proposed by Fukuoka et al [9]. Applying Galerkin's procedure and using Parseval's theorem as above in the analysis of HTS MSR results in the following set of equations: ...
Microwave characteristics of planar high temperature superconducting microstrip line
resonator (MSR) and coplanar waveguide (CPW) resonators have been estimated using a
full wave spectral domain technique in conjunction with the complex resistive boundary
condition. The computer aided design method developed is applied to simulate the
characteristics of planar resonators. The proposed method has been validated with
experimental results after taking into account the practical operating conditions. A reasonable
agreement for the theoretically computed and measured resonant frequency and unloaded
Q-value with experimental data of Porch et al (1995 IEEE Microw. Theory Technol. 2
306–14) has been observed for the MSR operated at 5 GHz as well as for the CPW
resonator at 7.95 GHz.
The introduction of electro-optic sampling techniques now allows the study of very high speed pulse propagation on planar transmission lines. In the frequency domain, recent work on microstrip and coplanar waveguides (CPW) on semiconductor substrates has shown the existence of slow-wave phenomena [1][2]. Since these phenomena are frequency dependent, strong dispersive effects on picosecond pulses would be expected. For a lossless substrate, a spectral domain technique has been used to calculate pulse dispersion for a coplanar waveguide (CPW) and coplanar strips [3], and for a particular geometry and lossy layer both mode matching and finite element techniques have been used to predict pulse behavior in microstrip and CPW [4]. In a typical structure exhibiting strong slow wave effects there are three distinct layers in the substrate: first, a thin, lossless spacer layer immediately below the CPW; second, a somewhat thicker lossy (i.e. doped) layer; and third, a very thick lossless layer. The slow-wave phenomenon (and corresponding variation in effective dielectric constant) occurs as a result of the different interactions of the electric and magnetic fields of the propagating wave with the lossy layer below the CPW. The complex effective dielectric constant of the guide is a function of the conductivity of the lossy layer, the separation of the CPW from this layer, the transmission line dimensions, and the frequency. For frequency domain applications, we have recently proposed a new method to control the slow wave factor in these structures by replacing the doped lossy layer with an (CW) optically generating electron-hole plasma layer in the semiconductor substrate [5]. The device could then serve as a phase-shifter, controlled by varying the optical excitation level, and thus the conductivity of the lossy layer. In this paper we discuss the the effects of the lossy layer on picosecond pulse dispersion.
Ce texte est le résumé des travaux sur les méthodes numériques 2D et 3D en électromagnétisme entrepris entre 1989 et 1999 dans les deux laboratoires :
* Laboratoire de Micro-ondes, INP-ENSEEIHT, Toulouse
* Laboratoire d'Hyperfréquence et Caractérisation (LAHC), Chambéry
Le développement détaillé de trois méthodes est présenté :
* Méthode Variationnelle Multimodale
* Méthode de Résonance Transverse Modifiée
* Méthode de l'Opérateur Transverse
Ainsi que leurs applications aux circuits hyperfréquences passifs.
Today’s state of the art VLSI circuits, microwave integrated circuits, and next generation VLSI or ULSI circuit designs face new challenging problems, that is, signal integrity problems. With the advent of deep submicron semiconductor processing technology, there has been rapid development of IC with integration of more than several hundred million transistors. These VLSI circuits will be operated with clock frequencies greater than several GHz. However, such an increase of integration level and speed raises the risk of poor noise margins and timing malfunctions during circuit operations. Therefore, when designing high performance VLSI circuits, very accurate design methodologies are required.
IC interconnect transmission line effects due to the characteristics of a silicon substrate and current return path impedances are physically investigated and experimentally characterized. With the investigation, a novel transmission line model is developed, taking these effects into account. Then an accurate signal delay on the IC interconnect lines is analyzed by using the transmission line model. The transmission line effects of the metal-insulator-semiconductor IC interconnect structure are experimentally verified with s-parameter-based wafer level signal-transient characterizations for various test patterns. They are designed and fabricated with a 0.35 μm CMOS process technology. Throughout this work, it is demonstrated that the conventional ideal RC- or RLC-model of the IC interconnects without considering these detailed physical phenomena is not accurate enough to verify the pico-second level timing of high-performance VLSI circuits.
Magnetic materials are fundamental part of non-reciprocal microwave components such as isolators and circulators. In order to improve the effect of the isolation, new materials with magnetic anisotropy were studied such as composites, but the determination of their magnetic properties is still a non-trivial mission. While the miniaturization of these microwave components is becoming more compulsory, a new characterization method suitable for thin magnetic layers is presented. The described technique allows the estimation of diagonal and extra-diagonal components of the permeability tensor.
Coplanar waveguide (CPW) has been suggested as an alternate to microstrip for microwave and millimeter-wave monolithic integrated circuits. It has been found to be well suited for use with field effect transistors (FETs), it enjoys some specific advantages and suffers from several drawbacks compared to microstrip. A brief survey of the characteristic features of CPW has been presented. The general characteristics of CPW eg, characteristic impedance, propagation constant and loss. Including the effect of dispersion and discontinuities are discussed with emphasis on the environmental constraints. Special reference is made to the development of components and circuits using CPW guiding structures.
A simple analytical model is developed for a slow-wave monolithic microwave variable phase shifter. Propagation characteristics of the phase shifter were evaluated using this model and were found to be in excellent agreement with the experimental results of Neidert and Krowne. The model permits changing various parameters to optimize phase-shifter performance with relative ease.
Two novel kinds of circles on the Smith chart are introduced, which allow, in designing low-noise microwave amplifiers, taking into account the level of the input match. Outlines of design procedures for using these circles are also given.
Professor Tatsuo Itoh acquired his professional
work ethic at a young age. Waking up well before dawn
to help with deliveries in his father’s milk business, spending
the day in classes, the evening doing tutoring, and much of the
time between twilight and dawn on his schoolwork, Itoh had
little time for any self-indulgence. One of three boys growing
up in the Yokosuka Naval district, south of Yokohama, Japan,
immediately following World War II, Tatsuo remembers playing
with handmade toys, especially wooden trains and paper objects
he fashioned himself. His parents had graduated from teachers’
colleges and had been school teachers before the war, but his
father had a difficult time getting steady work in the reconstruction
years. They both had strong commitments to learning and
they sent Tatsuo to a Jesuit high school with the best reputation
for quality teaching in the district. Eiko Gakuen still exists
today and is ranked in the top 10 of 4000 high schools in Japan.
A method of measuring the properties of micron-sized slow-wave coplanar transmission lines is presented. The transmission line's propagation constant γ and characteristic impedance Zo are determined directly from the measured S-parameters of a section of transmission line. Measurements are made with microwave "on-wafer" probes. Test data from 0.5 to 40 GHz is presented on a relatively low-loss slow-wave coplanar transmission line fabricated on silicon. The measured quality factor of the transmission line is seen to approach 10 at 11 GHz with a wavelength-compression factor of approximately 5.6.
Propagation and losses for some quasiplanar transmission structures will be characterized by using an accurate and fast quasi-analytical solution. This latter is derived from a recently proposed modified transverse resonance method (MTRM), in which an analytical preprocessing has been introduced. The quasistatic contribution is obtained by an entirely analytical solution, so the resultant system of linear equations is very efficient. Furthermore, the resistive boundary conditions as well as the complex substrate permittivity are taken into account in an intrinsic manner, leading to an accurate determination of dielectric and conductor losses in lossy transmission lines.
Through-silicon vias (TSVs) in low, medium and high resistivity silicon for 3-D chip integration and interposers are modeled and thoroughly characterized from 100 MHz to 130 GHz, considering the slow-wave, dielectric quasi-TEM and skin-effect modes. The frequency ranges of these modes and their transitions are predicted using resistivity-frequency domain charts. The impact of the modes on signal integrity is quantified, and three coaxial TSV configurations are proposed to minimize this impact. Finally, conventional expressions for calculating the per-unit-length circuit parameters of transmission lines are extended and used to analytically capture the frequency dependent behavior of TSVs, considering the impact of the mixed dielectric (silicon dioxide-silicon-silicon dioxide) around the TSVs. Excellent correlation is obtained between the analytical calculations using the extended expressions and electromagnetic field simulations up to 130 GHz. These extended expressions can be implemented directly in electronic design automation tools to facilitate performance evaluation of TSVs, prior to system design.
The tools and techniques to fully leverage coplanar technology Coplanar Microwave Integrated Circuits sets forth the theoretical underpinnings of coplanar waveguides and thoroughly examines the various coplanar components such as discontinuities, lumped elements, resonators, couplers, and filters, which are essential for microwave integrated circuit design. Based on the results of his own research findings, the author effectively demonstrates the many advantages of coplanar waveguide technology for modern circuit design. Following a brief introductory chapter, the text thoroughly covers the material needed for successful design and realization of coplanar microwave circuits, including: * Fundamental transmission properties of coplanar waveguides using a full wave analysis * Detailed analysis of most discontinuities used in coplanar waveguide design * Lumped elements in coplanar technology that are needed in circuit design * Development of software for coplanar circuit design, including a CD-ROM containing a test version of the software for modeling coplanar circuit components and circuits * Application of derived results to build more complex components such as lumped element filters, waveguide filters, millimeter wave filters, end-coupled waveguide structures, waveguide couplers, and Wilkinson couplers for different frequency ranges in coplanar technology The final chapter focuses on special coplanar microwave integrated circuits that have been developed using the software presented in the text. The book concludes with a thought-provoking discussion of the advantages and disadvantages of the coplanar technique. Extensive use of figures and tables helps readers easily digest and visualize complex concepts. A bibliography is included at the end of each chapter for further study and research. Coplanar Microwave Integrated Circuits is recommended for graduate students and engineers in RF microwaves who want to reap all the advantages and possibilities of coplanar technology.
A simple quasi-TEM analysis of 'slow-wave' mode propagation on micron-size coplanar metal-insulator-semiconductor (MIS) transmission lines on heavily doped semiconductors is presented, and theoretical results are compared with measurements on four such structures at frequencies from 1.0 to 12.4 GHz. Excellent agreement is found, which shows that the 'slow-wave' mode propagating on these transmission lines is, in fact, a quasi-TEM mode. Relatively low-loss propagation along with significant wavelength reduction is observed. Conduction losses of the metal are included in the theory and are shown to dominate the attenuation at frequencies below 25 GHz and to still be significant at frequencies up to at least 100 GHz.
The dispersion of a picosecond pulse propagating along a coplanar waveguide on a semiconductor substrate is studied. Numerical calculations are used to predict the pulse shape for varying carrier concentrations in a multilayer AlGaAs/GaAs/AlGaAs structure.
Propagation and losses for some quasiplanar transmission structures will be characterized by using an accurate and fast quasi-analytical solution. This latter is derived from a recently proposed modified transverse resonance method (MTRM), in which an analytical preprocessing has been introduced. The quasistatic contribution is obtained by an entirely analytical solution, so the resultant system of linear equations is very efficient. Furthermore, the resistive boundary conditions as well as the complex substrate permittivity are taken into account in an intrinsic manner, leading to an accurate determination of dielectric and conductor losses in lossy transmission lines.
The author reviews guided wave phenomena in a transmission line on a heterostructure semiconductor in which slow wave propagation is generated by optical illumination. The device consists of a heterostructure in which a GaAs layer is sandwiched by GaAlAs layers. A typical planar transmission line such as a coplanar waveguide is formed on the top surface. Experimental results are given. The measurement was done at illumination intensities of 3.2 mW/cm2, 32.0 mW/cm 2, and 63.7 mW/cm2. A maximum relative phase shift of 60° at 9.5 GHz was observed for an illumination of 3.2 mW/cm2. The present work is directed toward the development of an optically controlled phase shifter in a form compatible with monolithic microwave integrated circuit techniques
Several approaches, using different forms of Green's functions, are presented for the two-dimensional analysis of slow-wave structures which are used in monolithic microwave integrated circuits. It is shown that these methods lead to an accurate determination of the depletion layer profile in the metal-semiconductor structure, allowing an adequate modelling of the corresponding cross-section. The most significant characteristics of a quasi-TEM slow-wave propagation, namely the slowing factor and attenuation constant, are calculated and in some cases the obtained theoretical results are shown to be in good agreement with available experimental data. It is also demonstrated that these methods allow to study single- and dual-gate travelling-wave field effect transistors by means of a simple change in the boundary conditions and that in this case, a "small-signal approach" conducts directly to the evaluation of complex inter-electrode impedances.
A rigorous analysis of the field effect transistor MESFET using Green's functions and taking into account the wave propagation phenomenon is developed in the presented study. In this case, an analytical model is given to determine the characteristics of the MESFET, such as the S-parameters and gain. Numerical results are compared with experimental published data with good agreement.
A general analysis of non-linear wave propagation along transmission lines with voltage-dependent capacitance is presented. In particular, slow-wave structures like MIS and Schottky-barrier strip lines are examined. A spatial periodicity is included explicitly. The theoretical treatment is based on suitable equivalent circuits leading to characteristic wave equations. With regard to practical devices, the solutions show a variety of different phenomena as determined by the parameters of the non-linearity, dispersion and dissipation and the boundary conditions. Experimental results performed on a slow-wave model line are included.
A wave-theoretic analysis of MESFET electrode structures is presented where for the first time both the losses caused by the semiconductor layer and those caused by the finite conductivity of the electrodes are taken into consideration. The active properties of the transistor are modelled by adopting a suitable small-signal theory. The results are discussed by taking as an example a TW FET design, although they are equally relevant for all standard microwave MESFETs.
A finite element simulation has been implemented to evaluate the slow wave mode propagation characteristics in metal-insulator-semiconductor waveguiding structures. Particular emphasis has been placed on coplanar waveguides compatible with silicon integrated circuit, with an objective of evaluating the effect of inhomogeneous doping on propagation characteristics. The simulator has been benchmarked successfully against a number of cases presented in the literature (usually within five to ten %), including MIS coplanar waveguides. The effect of inhomogeneos doping and finite metallization in maintaining a large slowing factor while reducing the attenuation constant and increasing transmission line Q is presented, and constraints on slow wave mode passive components are discussed.
Modeling and testing of monolithic coplanar waveguide (CPW) phase shifters using both optical and Schottky-contact control techniques have been performed. Simulation work on a periodically illuminated structure has been completed, showing that some improvement in performance may be possible, although with a reduction in frequency bandwidth. CPW transmission lines have been fabricated on semi-insulating GaAs, on lightly and heavily doped epi GaAs, and on AlGaAs/GaAs heterostructure, and electrical characterization has been performed. Both Schottky-bias controlled mechanism, using constant D.C. bias while using optical control has also been developed, which has yielded the best experimental performance to date for a distributed CPW phase shifter.
This technical report describes traveling-wave optical modulators using cross-tie slow-wave electrodes on GaAs substrates as well as wideband feeding of a coplanar strip electrode. Periodic cross-tie conductors are overlaid on a modulated coplanar strip and a modulated coplanar waveguide electrode to make slow-wave electrodes. In these structures, phase velocity matching between modulation and optical waves is satisfied over a very wide bandwidth by reducing the phase velocity of the modulation wave using the slow- wave electrodes. Therefore, the modulation bandwidths are greatly increased while the dominant conductor losses are relatively high and limit the bandwidths. The coplanar strip slow-wave structure has been build on a semi- insulating GaAs substrate and measured using a microwave network analyzer. The measured phase velocity is much lower than those of conventional coplanar electrodes and agrees very well with the calculated one. Keywords: Optical communications; Optical signal processing.
The crosstie-overlay slow-wave structure is proposed as a passive circuit element in monolithic microwave integrated circuits. The propagation characteristics of the crosstie-overlay slow-wave structure are analyzed both analytically and experimentally. In analysis, a method suitable for design as well as a rigorous two-dimensional spectral domain method for accurate results are developed. The results obtained in analysis are checked with experimental results. They are in good agreement. A modified structure is proposed to reduce the conductor loss. Distributed Chebychev bandstop filters utilizing the slow- wave structure are designed. Another circuit application of the slow-wave structure, frequency scanning antenna, is also investigated. (rrh)
In this project, mode matching was used to calculate the propagation constant and the characteristic impedance of a coplanar coupled microstrip line. The Striplines are considered to be perfect electric conductors of negligible thickness, and are separated from the ground plane by three layers of dielectric material. The layer with the higher dielectric constant is sandwiched between two layers of lower dielectric constants, such that the field is confined to this middle layer, which is called the 'conducting layer' of the microstrip line. By confining the field to this layer, losses at the metal conductor are minimized.
The most significant computational techniques for the analysis of printed circuit transmission lines fabricated on semiconductor substrates are critically reviewed. Attention is focused on metal-insulator-semiconductor structures for slow-wave applications. Qualitative results on the propagation characteristics of microstrip lines can be drawn using the Transverse Resonance approach to parallel-plate model of the microstrip. Among rigorous full-wave techniques, in addition to the Spectral Domain Method and the Mode-Matching technique, the Modified Mode Matching method is introduced, which combines advantages of both methods. In addition, semi-empirical equivalent circuit models, useful for CAD applications but valid in limited ranges of the relevant parameters, are described, along with strictly numerically oriented approaches such as the Finite Element method for the analysis of complicated geometries.
CAD-oriented analytic formulas are presented for calculating the quasistatic TEM parameters of the overlayed supported asymmetric coplanar waveguides (OSACPW). The effect of the thicknesses and the dielectric constants of the overlaying and supporting materials on the quasistatic parameters has been investigated by using the expressions derived by the conformal mapping techniques. Comparisons have also been made between this article's results and the results available in the literature for the conventional coplanar waveguide (CPW) and the asymmetric coplanar waveguide (ACPW). It has been shown that the present formulas can also be used for calculating the quasistatic TEM parameters of the line structures such as the open, the open supported, and the overlayed supported CPW or ACPW. © 1996 John Wiley & Sons, Inc.
A field-theoretical analysis of conductor loss on planar transmission lines is presented. The full-wave approach employed holds for arbitrary values of metallization thickness and skin depth. Its validity is checked by comparison to measurement data on coplanar waveguide (CPW). The results are discussed and compared with modeling approaches available so far. The considerations concentrate on the CPW case where, in contrast to the microstrip structures used in hybrid ICs, a significant influence of the fields inside the lossy conductors can be detected. Finally, conclusions regarding both millimeter-wave integrated circuit design and modeling are drawn. © 1992 John Wiley & Sons, Inc.
For CAD simulation, it is necessary to determine the frequency behavior of coplanar lines laid on semiconductor substrates. Exact analyses can be performed using numerical techniques such as SDA or mode matching. However such analyses cannot be included in CA D programs. For this purpose, we present an original model for coplanar lines laid on semiconductor substrates, which takes into account both the influence of thickness metallization and dielectric cap layer. The validity of our model is tested by comparison with mode-matching and SDA results. The influence of metallic losses is quantified and taken into account for micronic structures.
When the strip line containing a semiconductor material is illuminated by light with an energy larger than the band gap, the resistivity of the semiconductor changes and the control of the microwave propagation in the line can be realized. For high-speed control it is necessary to use the semiconductor with short lifetime and to increase the intensity of illuminating light. In this paper, a fundamental study has been performed for the microwave modulator using photoconductivity. Strip lines suitable for this modulator are a coplanar waveguide and a slot line. This paper investigates the coplanar waveguide. An optimum structure is found that provides the strongest microwave attenuation for a given light intensity. The dependence on the frequency of the attenuation constant is also found. The analysis is based on the spectral domain method. To confirm the usefulness of the modulator proposed here, the modulator has been made of Si and tested at 10 GHz. It is found that the modulation up to 100 kHz is possible even with a light source such as a lightemitting diode.
A comprehensive analysis procedure is presented to investigate mode propagation in a class of semiconductor-based transmission lines suitable for application in microwave or optoelectronic circuits. The method of lines (MoL) has been used to investigate single or multiconductor planar transmission line structures printed on a combination of insulating and semiconducting substrate. Homogeneous as well as inhomogeneous doping areas in the semiconductor are included in the theoretical formulation. Numerical results are presented for III–V semiconductor travelling wave electro-optic modulators in double-rib, multilayer strip waveguide configuration, microslabTM transmission lines with partial and full strip cover and slow-wave MIS microstrip/coplanar transmission lines on thick and thin film semiconductor substrate with gradually inhomogeneous doping layer.
The characteristics of a periodically-illuminated CPW phase shifter are investigated by the spectral domain approach combined with the cascaded transmission line matrix method. It is found that the phase shifter characteristics can be improved by appropriate use of periodic illumination instead of uniform illumination.
Attention to the microwave design of waveguide photodetectors
leads to travelling-wave photodetectors. These devices show bandwidths
as high as 172 GHz, the highest reported for a p-i-n photodetector, and
bandwidth efficiency products as large as 76 GHz, the largest reported
for any photodetector without gain. Direct comparisons with vertically
illuminated and waveguide photodetectors confirm the advantages of
travelling-wave photodetectors
Finite Ground Coplanar (FGC) waveguide transmission lines on CMOS grade silicon wafer (¿<0.01 ohm-cm) with a thick embedded silicon oxide layer have been developed using micromachining techniques. Lines with different lengths were designed, fabricated and measured. Measured attenuation and s-parameters are presented in the paper. Results show that the attenuation loss of the fabricated FGC lines is as low as 3.2 dB/cm at 40 GHz.
This paper presents a full-wave investigation on the coupling between odd and even modes in CPW two-poles resonators from an integral wave-based formulation. Electric field and current density sources are considered and confronted for the excitation of the CPW odd and even modes. The efficiency of a coupling notch introduced to control the coupling ratio between the even and odd modes is rigorously determined. A simple and efficient electromagnetic modelling of Air-bridges, easy to include in a CAD environment, is proposed. The influence of the Air-bridges height, the effect of the position and nature of the exciting sources on the resonant frequencies and on the S-parameters are examined.
We report an investigation of novel slow-wave ladder microstrip line bandpass filters. The investigation has shown that the ladder microstrip line filters can be designed based on the knowledge of the conventional microstrip coupled line filters. The new type of filter has a smaller size than the conventional one because of the slowwave effect on the ladder line. Two filters of this type have for the first time been designed and fabricated. The measured performances are presented.
In this contribution we provide a full-wave analysis of the effect of conductor losses in MIS and Schottky junction devices. This rigorous treatment explains the fundamental mechanism controlling dispersion in real planar circuits and theoretical data are in good agreement with experimental and FDTD results from other sources.
A finite element field analysis program is developed to study the effect of localized finite conductivity region in the Schottky-contact CPW in the slow-wave application. Theoretical results obtained for the MIS (layered) CPW structure show good agreements with those in the existing literature. Our analysis indicates the new Schottky-contact slow-wave CPW structure under analysis is viable for low loss and wideband electronically tunable phase shifter application.
For CAD simulation, it is necessary to determine the frequency behaviour of coplanar lines laid on semiconductor substrates. Exact analysis can be performed by using numerical technics such as S.D.A. or Mode Matching. However such analysis can not be included in C.A.D. programs. For this purpose, we present an original model for coplanar lines laid on semiconductor substrates, which take into account both the influence of thickness metallization and dielectric cap layer. The validity of our models is tested by comparison with mode matching and S.D.A. results.
A full-wave mode matching analysis is applied to a slow-wave coplanar waveguide with finite conductor thickness on a lossy substrate. The time domain response is computed by knowing the accurate frequency domain data. The analysis is for the designs of high speed digital and wideband analog integrated circuits.
A parallel-plate waveguide model for the microstrip line formed on the Si-SiO2 system is analyzed theoretically and the results are compared with the experiment. The experiment has been performed over wide ranges of frequency, substrate resistivity, and strip width. Existence of three types of fundamental modes is concluded and the condition for the appearance of each mode is clarified. In particular, the slow-wave mode is found to propagate within the resistivity-frequency range suited to the monolithic circuit technology, and its propagation mechanism is discussed. Approximate analysis of the fringing effect is also made for the slow-wave mode.
The latest advances in microwave GaAs power FET device and circuit technologies are discussed. Optimum device structures and design parameters for operating frequencies up to K-band are covered. Broadband matching networks for hybrid power GaAs FET amplifiers are described. These matching networks were obtained with CAD technique, using FET equivalent circuit models deduced from S-parameter characterization and modified for large-signal operation. Progress in the design and performance of monolithic power FET amplifiers is also presented.
A method is described for the exact calculation of the field distributions and the phase constants of single and coupled dielectric image lines. The theoretical results have been proved by experiments with dielectric image lines fabricated of casting resins.
A two dimensional analysis of MIS (or Schottky contact) microstrip is made with the aid of the finite element method. Theoretical results are compared with experimental results.
The mode-matching technique is employed for computing the propagation constants and field distributions of an inverted strip dielectric waveguide. The results derived in this manner are further improved by using variational formulas expressly designed for open dielectric waveguides. Illustrative numerical results are presented and compared with experimental measurements as well as those based on approximate methods found in the literature.
In M.I.C. technology it is important to know well the propagation properties of planar lines laid on semiconductor substrates. For this purpose we have developped two complementary theoretical analysis. The first one based on the Finite Element Method (F.E.M.), the second one on Spectral Domain Approach (S.D.A.). We present some attemps of these analysis which are compared to experimental results.
Planar transmission lines formed with MIS and Schottky barrier contacts are analysed based on the spectral domain technique. Depending on the frequency and the resistivity of the substrates, three different types of fundamental modes are predicted. The calculated slow-wave factors and attenuation constants agree well with experimental results.
Slow-wave characteristics of a coplanar waveguide with substrate resistivity are analysed using the mode-matching technique. This waveguide is suitable for microwave monolithic integrated circuits because of its coplanar configuration. Numerical results are presented and compared with an experimental measurement in the literature.
Cohn's method of analysis of the slot line on a dielectric substrate is extended to the case of integrated lines on a lossy inhomogeneous substrate. The slow-wave characteristics of the metal-insulator-semiconductor coplanar waveguide for MMIC applications are calculated and found to be in good agreement with the experiments.
The realisation of distributed microwave integrated circuits can be expected by using very low phase velocity propagation modes on MIS and Schottky planar transmission lines. Up to now, the frequency behaviour of such lines has been obtained by using analytical models. We present a rigorous analysis of a MIS microstrip line, the validity of which is testified by comparison to experimental values.
Novel slow-wave coplanai striplines on GaAs substrates with m.i.s. or Schottky junctions are described. With these lines, significant reductions in wavelength and bias-dependent behaviours can be achieved at microwave frequencies. The new lines seem potentially very useful for monolithic integration of microwave circuits involving GaAs m.e.s.f.e.t.s.
Schottky contact lines are a form of microstrip on a semiconducting substrate, the strip of which forms a rectifying metal¿semiconductor contact. Such a line has an extremely low phase velocity that is determined by the ratio of the depletion-region width to the substrate thickness, i.e. by the bias. Measurements agree well with theoretical expressions that are deduced from a parallel-plate-waveguide model.
Monolithic microwave integrated circuits based on silicon-on-sapphire (SOS) and gallium arsenide technologies are being considered seriously as viable candidates for satellite communication systems, airborne radar, and other applications. The low-loss properties of sapphire and semi-insulating GaAs substrates, combined with the excellent microwave performance of metal-semiconductor FET's (MESFET's), allows, for the first time, a truly monolithic approach to microwave integrated circuits. By monolithic we mean an approach wherein all passive and active circuit elements and interconnections are formed into the bulk, or onto the surface of the substrate by some deposition scheme, such as epitaxy, ion implantation, sputtering, evaporation, and other methods. The importance of this development is that microwave applications such as airborne phased-array systems based on a large number of identical circuits and requiring small physical volume and/or light weight, may, finally, become cost effective. The paper covers in some detail the design considerations that must be applied to monolithic microwave circuits in general, and to gallium arsenide circuits in particular. The important role being played by computer-aided design techniques is stressed. Numerous examples of monolithic circuits and components which illustrate the design principles are described. These provide a cross section of the world-wide effort in this field. A glimpse into the future prospects of monolithic microwave circuits is made.
A simple method for formulating the dyadic Green's functions in the spectral domain is presented for generalized printed transmission Iines which contain several dielectric layers and conductors appearing at several dielectric interfaces. The method is based on the transverse equivalent transmission line for a spectral wave and on a simple coordinate transformation. This formulation process is so simple that often it is accomplished almost by inspection of the physical cross-sectional structure of the transmission line. The method is applied to a new versatile transmission line, a microstrip-slot Iine, and some numerical results are presented.
The spectral domain analysis is applied for deriving despersion characteristics of dominant and higher order modes in fin-line structures. In addition to the propagation constantant, the characteristic impedance is calculated based on the power-voltage definition. Numerical results are compared for different choices of basis functions and allow to estimate the accuracy of the solution.
The mode-matching technique is employed for computing the propagation constants and field distributions of an inverted strip dielectric waveguide. The results derived in this manner are further improved by using variational formulas expressly designed for open dielectric waveguides. Illustrative numerical results are presented and compared with an experimental measurement as well as those based on approximate methods found in the literature.
A method is described for the exact calculation of the field distributions and the phase constants of single and coupled dielectric image lines of rectangular cross section. Field distributions and phase constants calculated by this method are presented as well as experimental results from lines fabricated of paraffin wax. The physical properties of the electromagnetic fields and the mode designation are discussed. The theory is compared to approximate calculation methods known from the literature.
A frequency-dependent hybrid-mode analysis of single and coupled slots and coplanar strips is presented. The dispersion characteristic and characteristic impedance of the structures are obtained by applying a Fourier transform technique and evaluating the resulting expressions numerically using the method of moments. Numerical results are presented and compared with results published by other investigators. The experimental performance of a slot-line coupler is compared with predicted performance based upon the results presented here for coupled slots. Excellent agreement has been obtained in all cases.
The parallel-plate waveguide with a two-layer loading medium, a conducting semiconductor substrate, and a relatively thin dielectric layer approximates the interconnections in many integrated systems if the fringing fields are ignored. The fundamental mode of this structure is an E mode which is a surface wave. Its propagation behavior is analyzed in this paper and the equations are evaluated by highly accurate numerical methods. The semiconducting substrate is characterized by its dielectric constant and conductivity. A critical conductivity /spl sigma//sub min/ exists and is related to the cross sectional and material parameters. If the substrate conductivity is given by /spl sigma//sub min/ then the attenuation constant of the line is a minimum. The same value of conductivity yields minimum phase distortion at maximum bandwidth. If the conductivity is larger than /spl sigma//sub min/ the substrate acts as a poor conductor with associated skin effect; if it is smaller, lossy dielectric behavior results. Analysis shows that it is appropriate to subdivide the frequency range into three intervals. The lowest-frequency interval is characterized by propagation which resembles diffusion. This is caused by the loss in the dielectric layer. The next frequency range extends to some upper frequency which is determined by substrate conductivity and the cross-sectional dimensions. In this interval, the phase velocity of the fundamental mode is controlled by the ratio of dielectric to semiconductor thickness, which, if typical interconnections are considered, implies a very low velocity. This property indicates that the structure can serve as a delay line. Further increases in frequency result in higher phase velocities. Skin effect and dielectric loss behavior describe the propagation in this third interval.
It is shown that metal-insulatior-semiconductor (MIS) and Schottky-barrier microstrip structures having substrate resistivities within a certain range propagate slow waves with phase velocities that are dependent upon the instantaneous voltage at each point along the line. This and other useful properties of these microstrips can be used advantageously in a number of microwave devices. Loss measurements for the MIS microstrip structure confirm the predictred frequency dependence of the attenuation constant. While the levels of measured attenuation presently achieved are fairly high (4.5 dB/cm at 1 GHz), several methods for reducing the attenuation are proposed. A number of devices are discussed, including an electronically variable phase shifter for which attenuation and phase-shift measurements are presented.
A short highly variable VHF delay line is described, in which variability is achieved by changing the primary volume of electric field energy storage. It is fabricated using well-established planar integrated-circuit techniques.
Monolithic MIC's gain momentum as GaAs MSI nears
- F J Moncrief
Dispersion characteristics of shielded microstrips with finite thickness
- G Kowalski
- R Pregla