Generalized Transmission Line Research Articles

An analysis of electromagnetic interference on RF circuits based on electromagnetic topology

ABSTRACTIn this article, we propose a method of analysis of the intentional electromagnetic interference (IEMI) in radio frequency circuits that are directly exposed to an external electromagnetic wave, using electromagnetic topology (EMT). EMT solves IEMI problems, by a fast and efficient transformation of the main penetrating channels of the external electromagnetic wave in the target, into general equivalent transmission lines. To handle nonlinear devices, we combined EMT with the harmonic balance method, by applying the least square method to the experimental data of the devices. To verify the proposed method, we applied it to microstrip line circuits with passive loads, a dipole antenna, and a low noise amplifier, and compared the results with the experimental ones. The two results were in good agreement. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2784–2789, 2014

Fast Prediction and Optimal Design for Eye-Height Performance of Mismatched Transmission Lines

As the data rate becomes higher, the intersymbol interference influences the signal quality more seriously. In this paper, a simple methodology is presented to predict eye height for general transmission line systems with mismatched source and load terminations. Simple formulas are derived to estimate the eye height with the consideration of the reflection coefficients at both ends, the loss constant, and a matched pulse response of the transmission line for the cases of long and short transmission lines. Furthermore, a contour map is successfully constructed to represent the variations of eye height versus the reflection coefficients and used to facilitate the termination design for the best signal integrity performance. Finally, the time domain simulations and experiments are also provided to verify the proposed methodology.

Numerical approach to generalized transmission line model and its application to Au/Sn/p-HgCdTe contact

A generalized transmission line model (TLM) and a compatible numerical method have been proposed to characterize metal-semiconductor contacts that exhibit nonlinear properties. This model and method have been applied to the analysis of Au/Sn/p-HgCdTe contact and have realized determination of related physical parameters by fitting experimental data. Our model's merit of avoiding the overestimation of barrier height active contact area encountered in other methods without TLM scheme is discussed. In addition, only by using this model, the transfer length can be credibly determined in the case of nonlinear contacts.

Broad frequency-band characterizations of electromagnetic energy propagation in planar thin-film transmission lines

Thin-film transmission lines are experimentally characterized in the frequency range from 10 MHz to 110 GHz. Scattering (S-) parameters for several test lines are measured. Then, two important transmission line parameters (i.e., the propagation constant and characteristic impedance) are determined in the measured frequency range. The resonances, which are inevitable in a practical experimental environment, are carefully eliminated by de-embedding parasitic effects and by determining the frequency-variant dielectric permittivity based on the Debye model. Based on the experimental work, we showed that the conventional skin-effect model may not be accurate for high-frequencies. Further, the 3-dimensional (3D) numerical field solver does not reflect the radiation loss at high-frequency. Finally, in the millimeter (mm)-wave region, all the three loss mechanisms due to the skin-effect, dielectric polarization, and electromagnetic radiation have to be taken into account.

Magnetic charge, magnetic current, magnetic scalar potential, and electric vector potential

ABSTRACTThis work presents a novel contribution to the analysis of magnetic structures, making use of several interrelated concepts such as, magnetic charge density, magnetic charge, magnetic current density, magnetic current intensity, magnetic voltage, magnetic scalar potential, and electric vector potential. These useful dual concepts arise in the analysis of Maxwell's equations when standard field sources, that is, electric charge density and electric current density are not directly at play. An application example is provided concerning the derivation of the telegrapher's equations that govern guided wave propagation in magnetic transmission lines. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1107–1111, 2014

Analysis of slow‐wave propagation in coplanar transmission lines with inkjet printed multiwalled carbon nanotubes network

AbstractThis article investigates the propagation along coplanar waveguide (CPW) structures, where multiwalled carbon nanotubes (MWCNTs) network layers are deposited using inkjet printing. Electrical parameters are extracted from measured S‐parameters data over the frequency range from 10 MHz to 26.5 GHz. The results clearly demonstrate two distinct propagation modes. At low‐frequencies, a slow‐wave factor up to 7 is achieved. With increasing frequency, attenuation becomes significant, while the propagation constant tends to a linear TEM regime. An equivalent lumped element circuit for CPW structure with MWCNTs network is developed and describes well the measured behavior up to 26.5 GHz. Thanks to the extracted equivalent circuit, the origin of the observed slow‐wave phenomenon is confirmed: it is ascribed to a larger capacitance per unit length of the CPW line induced by the presence of the CNTs network that prevents/limits the expansion of fields into air. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1118–1124, 2014

Some limiting aspects of transmission line theory and possible improvements

Wiring still supports most of electric power fluxes as well as data transmission in various infrastructures and transport systems. Hopefully, transmission line theory is a very helpful approximation to estimate interference propagation among cable harnesses. This is definitely a useful tool for engineers, since it enables anticipating the probability of failure of equipment they are connected to. Everything has been written from the initial roots of transmission line derivation, dated from the ancient telegraphist's equations established by O. Heaviside back to...1880! until the last developments of sophisticated and off-the-shelf transmission line solvers for complex arrangements of cable networks. The fact is, that these tools are so familiar to many EMC engineers that it might come with some misunderstanding of some results. In this paper, we take a look at the root assumptions of this approximate theory and examine some of its potential weaknesses, through simple examples. Then, we investigate the question of the possible improvement of the classical transmission line theory (when and if required). In principle, this would require the derivation of some kind of generalized transmission line theory or even the examination of the super theory of transmission lines. We rather show that a much more simple modification of transmission line equations is possible for a better approximation of the experimental observations.

Borehole Antenna Considerations in the EMRE System: Frequency Band 312.5-2500 kHz

The ElectroMagnetic Radiofrequency Echoing (EMRE) system is utilized in radiofrequency imaging (RIM) measurements between two deep boreholes. It is based on radiowave attenuation, making it possible to reconstruct the attenuation distribution of the borehole section (tomogram). The main parts of the EMRE system are a continuous wave (CW) transmitter and superheterodyne-type receiver. The insulated dipole antennas are the transducers between the device and environment, or together they form a transmission line. The system is bistatic because the antennas are placed in separate boreholes. When an antenna is situated in a dissipative medium, e.g. in a deep borehole, its performance becomes highly environmentally sensitive. Direct measurements of the feed-point current and radiative characteristics are impossible, and numerical models must therefore be used to investigate the borehole effects. A generalized transmission line model of an insulated antenna is a simple and useful way to examine the antenna-related properties. A drawback is that the borehole water must be excluded from the models due to the high wave number of water. The commercial simulation package FEKO is a numerical modelling package and a powerful tool when constructing more realistic antenna and borehole models. FEKO models and transmission line models (WKG, CHEN) were compared and the results coincided in the frequency band of 312.5-2500 kHz. According to the FEKO studies, the influence of borehole water and the location of the antenna in the borehole, i.e. centric or eccentric, did not appear to have a significant effect. The scattering parameter s11, the ratio of forward and returned power, is a useful antenna parameter to estimate the power level that is radiated from the antenna to the surrounding rock. According to the FEKO models, the highest measurement frequency (2500 kHz) of the EMRE system seems to suffer the most under the borehole conditions due to the low values of s11 (~-2dB). The performance level of the system determines the maximum distances (translumination distance) at which the signals are still detectable. According to the results using a simplified measurement geometry, the EMRE system can operate at distances of 10 000 Ωm and the lowest frequency of 312.5 kHz is used. At minor distances of 400-600 m, the system operates well at all frequencies.

Full-wave analysis of a compact bandpass meandering resonator filter using method of lines

Full-wave analysis based on the method of lines and the generalized transmission line equations is applied for the design of a small-size wide stopband bandpass filter. The analytical calculation in the direction of propagation and using nonequidistant discretization enables the analysis of the method of lines to be efficient for structures that can be divided into cascaded subsections along the propagation direction of the wave. The proposed filter consists of a pair of meandering uniform impedance resonators and feeding lines. Wide stopband and high selectivity as well as compact size of the filter are achieved due to the effect of multipath between the feeding points and the resonators that leads to suppression of the first and second harmonic of the filter. The modes distribution and the scattering parameters of the designed filter are computed and studied, leading to an achievement of a passband return loss greater than 18 dB and insertion loss about 1.7 dB. The designed filter is fabricated and tested, where good agreement is found between the numerical and experimental results.

Modeling and Analysis of Ladder-Network Transmission Lines with Capacitive and Inductive Lumped Elements

This paper examines the properties of wave propagation in transmission lines with periodic LC and CL cells, taking into account ohmic losses in resistors connected in series to lumped capacitors and inductors. First order time differential equations are derived for current and charge, thus allowing analysis of transient regimes of the lines being excited by a pulse of arbitrary shape. In particular we examine the propagation characteristics of periodic lines in which identical unit cells are repeated periodically and also discuss the interpretation of positive and negative phase velocities associated with the LC and CL topologies. Loss effects on the propagation bandwidths of both lines are also discussed, and it is shown that in the left-handed transmission line (CL configuration) the phase advance of the crest of the transmitted signal with respect to the source signal is due to the intrinsic dispersive nature of the CL line which, in contrast to the LC line, is highly dispersive at low propagation factors.

A Closed-Form Solution for Untransposed Transmission-Lines Fault Location With Nonsynchronized Terminals

This paper introduces a novel method for fault location in alternate current transmission lines relying on the voltage and current measurements in both line ends. The novelty of this method lies in the fact that there is no need for terminal synchronization and it can be applied to general untransposed transmission lines. The proposed formulation only applies a closed-form solution; thus, no iterative algorithm is required. Several simulated and real-world results are presented, and they show the effectiveness of the proposed approach.

TIME-DOMAIN DISTRIBUTED PARAMETERS TRANSMISSION LINE MODEL FOR TRANSIENT ANALYSIS

This article describes a time-domain transmission line model based on distributed parameters for transient analysis. This model is based directly on the difierential equations for the basic transmission line without any previous simpliflcation. The solution presented here for these difierential equations results in a more detailed time-domain model than others models currently in use, and with certain structural similarities with the distributed parameter frequency-domain model for long transmission lines. The deduction of a general time-domain transmission line model for fundamental frequencies parameters and single-phase line are presented in this article, but the model can also be extended to cases with multiconductor and frequency-depended parameters. In order to validate the model, a comparative test is presented to facilitate the analysis about the main similarities and difierences between this and other models.

Transmission line theory of collective plasma excitations in periodic two-dimensional electron systems: Finite plasmonic crystals and Tamm states

We present a comprehensive theory of the one-dimensional plasmonic crystal formed in the grating gated two-dimensional electron gas (2DEG) in semiconductor heterostructures. To describe collective plasma excitations in the 2DEG, we develop a generalized transmission line theoretical formalism consistent with the plasma hydrodynamic model. We then apply this formalism to analyze the plasmonic spectra of 2DEG systems with step-like periodic changes of electron density and/or gate screening. We show that in a periodically modulated 2DEG, a plasmonic crystal is formed and derive closed-form analytical expressions describing its energy band spectrum for both infinite and finite size crystals. Our results demonstrate a non-monotonic dependence of the plasmonic band gap width on the electron density modulation. At so-called transparency points where the plasmon propagates through the periodic 2DEG in a resonant manner, the plasmonic band gaps vanish. In semi-infinite plasmonic crystals, we demonstrate the formation of plasmonic Tamm states and analytically derive their energy dispersion and spatial localization. Finally, we present detailed numerical analysis of the plasmonic band structure of a finite four-period plasmonic crystal terminated either by an Ohmic contact or by an infinite barrier on each side. We trace the evolution of the plasmonic band spectrum, including the Tamm states, with changing electron density modulation and analyze the boundary conditions necessary for formation of the Tamm states. We also analyze interaction between the Tamm states formed at the opposite edges of the short length plasmonic crystal. The validity of our theoretical approach was confirmed in experimental studies of plasmonic crystals in short modulated plasmonic cavities which demonstrated excellent quantitative agreement between theory and experiment.

Generalization and Reduction of Line-Series-Shunt Calibration for Broadband GaAs and CMOS On-Wafer Scattering Parameter Measurements

This paper presents generalization and reduction of the line-series-shunt (LST) calibration technique, including generic parasitic treatments on the series/shunt standards and number reduction of calibration standards, for broadband GaAs and CMOS on-wafer scattering parameter ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameter) measurements. The series/shunt standards are modified with additional transmission-line (TL) sections on both the left and right sides to directly solve the five calibration parameters, namely, TL propagation constant, series impedance, shunt admittance, series parasitic admittance, and shunt parasitic impedance. This approach relaxes the constraint on the series/shunt standards that may not satisfy the plain lossy TL assumption in the parasitic evaluations. The calibration can be further reduced by only two standards if the lossy TL models for the series/shunt standards are satisfied. These points are examined by a microstrip test structure built on GaAs and CMOS technologies, with verification of an independent thru-reflect-line calibration.

Circuit model for efficient analysis and design of photonic crystal devices

We substitute different types of photonic crystal waveguide components by approximate transmission line circuits. The proposed distributed circuits exploit the analogy of wave propagation in photonic crystal waveguides and transmission lines. They are either cascaded to each other or inserted like stubs to imitate wave propagation within the photonic structure. Notable examples, e.g. coupled waveguide-cavity systems, sharp 90° bends, and T-junctions, are studied in detail. It is shown that analysis of the proposed circuits here can yield accurate enough results and thus substitute the brute-force numerical methods. The privilege of having analytical models is exploited to improve the performance of sharp 90° bends and T-junctions. The presented results are verified by using the standard finite-difference time domain (FDTD) method.

Fast and Efficient Analysis of Transmission Lines With Arbitrary Nonuniformities of Sub-Wavelength Scale

The Telegrapher's equations for a general nonuniform transmission line (NUTL) is analytically solved when the nonuniformities are of sub-wavelength scale. The proposed solution is based on an approximation of the chronological ordering operator for the Telegrapher's equations in an arbitrary NUTL. The proposed approximation is quite accurate when the transmission line has sub-wavelength nonuniformities. The scale of transmission line nonuniformity is assessed by using the concept of minimum resolvable length of nonuniformity (MRLN), which is based on the physically intuitive idea that electromagnetic waves are not affected by spectrally mild nonuniformities. The MRLN is inferred by using the spatial Fourier transform of the characteristics impedance of the NUTL. The proposed formulation is verified by using the measured scattering parameters of three different NUTLs.

Application of Generalized Transmission Line Models to MixedIonic-Electronic Transport Phenomena[Author's Correction

Application of Generalized Transmission Line Models to MixedIonic-Electronic Transport Phenomena[Author's Correction

Generalization of transmission line models for deriving the impedance of diffusion and porous media

System simulation and system identification are common problems in science and technology. In the field of electrochemistry this is of interest for systems, such as porous electrodes and mechanisms, such as diffusion. These are relevant for technical applications, such as energy storage and corrosion protection. Models describing the electrical behavior of such systems are based not only on schematics, physical and chemical approaches but also on equivalent circuits. Sometimes simplifications are applied to the conduction path and the spatial distribution of parameters. Due to the availability of many different models, the selection of a suitable model for a specific application is very difficult. Hence, identifying model similarities allows for a better understanding of each mechanism, reducing the number of mathematical calculations, simplifying model evaluation and thereby reducing the complexity. In this paper, a more general point of view of impedance in terms of a generalized transmission line model is considered. The differential equation of the transmission line model and its general solution is discussed. Furthermore, different boundary conditions are applied to obtain the solution for different electrochemical systems. The results for diffusion and porous electrodes are discussed in more detail, the solution of the differential equations are compared with the established models and the impedance behavior is analyzed. An effort has thus been made to analyze and remove ambiguity from impedance model equations. Removing ambiguity simplifies the analysis of model parameters influencing impedance behavior and additionally improves the robustness of nonlinear parameter optimization techniques.

Transmission-Line Model for Multiwall Carbon Nanotubes With Intershell Tunneling

The electromagnetic behavior of multiwall carbon nanotubes (MWCNTs), in the frequency range where only intraband transitions are allowed, depends on the combinations of different aspects: the number of effective conducting channels of each shell, the electron tunneling between adjacent shells, and the electromagnetic interaction between shells and the environment. This paper proposes a general transmission-line (TL) model for describing the propagation of electric signals along MWCNTs at microwave through terahertz frequencies that takes into account all these aspects. The dependence of the number of conducting channels of the single shell on the shell chirality and radius is described in the framework of the quasi-classical transport theory. The description of the intershell tunneling effects on the longitudinal transport of the π-electrons is carried on the basis of the density matrix formalism and Liouville's equation. The electromagnetic coupling between the shells and ground plane is described in the frame of the classical TL theory. The intershell tunneling qualitatively changes the form of the TL equations through the tunneling inductance and capacitance operators, which have to be added, respectively, in series to the (kinetic and magnetic) inductance matrix and in parallel to the (quantum and electrical) capacitance matrix. For carbon nanotube (CNT) lengths greater than 500 nm, the norm of the tunneling inductance operator is greater than 60% of the norm of the total inductance in the frequency range from gigahertz to terahertz. The tunneling inductance is responsible for a considerable coupling between the shells and gives rise to strong spatial dispersion. The model has been used to analyze the eigenmodes of a double-wall CNT above a ground plane. The intershell tunneling gives arise to strong anomalous dispersion in antisymmetrical modes.

Application of Generalized Transmission Line Models to Mixed Ionic-Electronic Transport Phenomena

Application of a generalized equivalent circuit including the electrode condition for the Hebb-Wagner polarization in the frequency domain proposed by Jamnik and Maier can provide a consistent set of material parameters, such as the geometric capacitance, partial conductivities, chemical capacitance or diffusivity, as well as electrode characteristics. Generalization of the shunt capacitors for the chemical capacitance by the constant phase elements (CPEs) was applied to a model mixed conducting system, Ag 2 S, with electron-blocking AgI electrodes and ion-blocking Pt electrodes. While little difference resulted for the electron-blocking cell with almost ideal Warburg behavior, severely non-ideal behavior in the case of Pt electrodes not only necessitates a generalized transmission line model with shunt CPEs but also requires modelling of the leakage in the cell approximately proportional to the cell conductance, which then leads to partial conductivity values consistent with the electron-blocking case. Chemical capacitance was found to be closer to the true material property in the electron-blocking cell while excessively high chemical capacitance without expected silver activity dependence resulted in the electron-blocking cell. A chemical storage effect at internal boundaries is suggested to explain the anomalies in the respective blocking configurations.