Lossy Transmission Lines Research Articles

Equilibrium-Independent Stability Analysis for Distribution Systems With Lossy Transmission Lines

Power distribution systems are becoming much more active with increased penetration of distributed energy resources. Because of the intermittent nature of these resources, the stability of distribution systems under large disturbances and time-varying conditions is becoming a key issue in practical operations. Because the transmission lines in distribution systems are lossy, standard approaches in power system stability analysis do not readily apply. In this paper, the stability of lossy distribution systems is certified by breaking the network into subsystems. By looking at the equilibrium-independent passivity of each subsystem, the stability of the whole network is implied by the diagonal stability of the interconnection matrix. This analysis scales to large networked systems with time-varying equilibria. The proposed method gracefully extrapolates between lossless and lossy systems, and provides a simple yet effective approach to optimize control efforts with guaranteed stability regions. Case studies verify that the proposed method is much less conservative than existing approaches.

Analysis of multiconductor transmission lines using the time domain method of lines

In this study, the solution of lossy multiconductor transmission lines is obtained using the numerical Time Domain Method of Lines (TDMoL). The TDMoL algorithm comprises discretizing a differential equation in the spatial dimensions and using an analytical solution in the time domain. This leads to high numerical accuracy compared with full-discretizing finite difference techniques which require a significant computational time and extensive memory. In addition, investigation of the numerical dispersion characteristics of the single and multiconductor lossy and lossless transmission lines engenders a time independent relation which proves the unconditionally stability and nondispersive property of the method. To examine the accuracy of the TDMoL, three different structures including a three-coupled uniform transmission line, a nonuniform coupled transmission line and a lossy interconnect with dynamic and functional crosstalk are evaluated. The results of the proposed methodology are validated by those of leap-frog finite difference time domain (LF-FDTD) method and ADS commercial software, and reveals up to 90% reduction in CPU time while maintaining the same degree of accuracy.

Transmission Line Fault Imaging Using Phaseless Inverse Scattering and Temporal Sparsity

A phaseless 1-D inverse scattering technique for detecting and imaging soft faults in lossy transmission lines is proposed. Its novelty is that it: 1) performs impedance profile imaging with only phaseless measurements and 2) integrates a temporal background subtraction sparsity technique to image temporal change across the impedance profile. The combination of these techniques removes the need for directional couplers and phase synchronization and reduces the required number of measurements. The novelty of the approach is that, even in its phaseless form, accurate linear expressions for the impedance profile are obtained, opening up significant flexibility in the techniques' application. Numerical and experimental results show that the proposed techniques provide accurate results for a wide range of impedance profiles with limited phaseless measurements. The techniques have the potential for providing low complexity systems for accurately monitoring the formation of newly formed transmission line faults.

Hybrid method for transient responses of transmission line in an apertured enclosure based on FETD method and transmission line equations

A hybrid method combining the finite-element time-domain (FETD) method and transmission line (TL) equations (FETD-TL) is presented for evaluating the transient responses of a lossy TL in an apertured rectangular enclosure excited by electromagnetic pulses. First, the electric fields in the enclosure without the TL are calculated based on the Bethe's small holes theory and the mirror procedure. Then, the enclosure's electric fields are introduced into the second-order TL equation for current as the equivalent distributed sources. The transient currents induced on the TL are obtained by solving the second-order TL equation for current based on the FETD method with a single iteration variable. Finally, the transient voltages induced on the TL are computed by discretising the first-order TL equation. Compared with the method based on finite-difference time-domain (FDTD) method and TL (FDTD-TL) via several examples, the proposed hybrid method is proved to be correct and effective, which possesses much higher convenience and efficiency than FDTD-TL method in dealing with TL model terminated by complex lumped parametric networks.

Time-Domain Software Correction of Nonlinear Faulty Lossy Transmission Line Networks

In this article, we use Newton's method and the nonlinear least squares method to solve a nonlinear problem in electromagnetic compatibility. Both techniques provide a way to identify the temporal profile of a voltage source that would produce a target voltage over a given time interval at a point of the transmission line network presenting nonlinear components. After comparing the results of a test problem, the most efficient method is considered to identify the temporal source in order to bring a software correction to a nonlinear faulty lossy transmission line network. The software correction process may cancel any unintentional perturbations produced by one or more faults regardless of their type and location.

Insertion Loss of Conductive Concrete Line Filters

Conductive concrete structures have been previously demonstrated to perform electromagnetic shielding that satisfied the shielding effectiveness requirements of military standard 188-125-1. The concrete mixture contains proportions of conductive materials together with taconite aggregate for the absorption of EM energy. This letter describes the conductive concrete filter concept as a lossy transmission line and reports the experimental results achieving broadband insertion loss that exceeds 100 dB.

Approach to modelling uniform transmission lines for broadband high‐frequency applications

A novel high-frequency lossy uniform transmission line model is presented in this study. Novel features include a compactness of form and a level of simplicity that confers enhanced simulation efficiency in practical applications. Although specifically developed to target implementation in generic versions of SPICE, the compact high-frequency model can be implemented using only four lines of netlist syntax in the case of circuit simulators that offer native Laplace equation support. Featuring a broadband frequency response characteristic that is defined by only four parameters, the compact HF model is based on a novel theoretical approach that elegantly connects the four model parameters to physical line parameters using only elementary line characterisation data. Important and perhaps surprising differences between the new model theory and classical textbook theory are highlighted and discussed. The lessons learned are then incorporated into a second hybrid model featuring a higher level of complexity that combines both new and classical theoretical approaches into a single set of model equations that are better suited for atypically small controlled impedance structures such as silicon interposers and on-chip clock and data distribution schemes.

Frequency- and Time-Domain Modeling and Characterization of PN Phase Shifters in All-Silicon Carrier-Depletion Modulators

We present a systematic study on PN junction phase shifters in silicon Mach–Zehnder modulators (MZMs) in both frequency and time domains, with an emphasis on their impact on MZMs’ RF loss. The RF loss associated with PN phase shifters dominates the overall RF loss of a MZM's transmission line and determines a MZM's bandwidth. The RF loss is also evident in the time domain, which for the first time is investigated. We find that the dielectric loss and conductor loss of a PN-loaded, lossy transmission line result in downhill and uphill features on the instantaneous impedance curve, which features are typically observed on the instantaneous impedance of an inductor and a capacitor, respectively. This is aligned with our model, which shows that the impedance of a PN-loaded lossy line includes an inductor term and a capacitor term and their values are expressed in terms of RF loss. Our model on RF loss and impedance agrees well with experiment in both domains for a variety of doping levels. Finally, we conduct performance test on modulators and discuss the constraints on the baud-rates and BERs in our QAM tests.

Time-Domain Procedures for Lightning-Induced Voltage Calculation in Electromagnetic Transient Simulators

In this paper, two time-domain procedures are proposed for the calculation of lightning-induced voltages using lossy transmission line models available in electromagnetic transient simulators. In both procedures, the influence of the incident electromagnetic field is represented in the form of current sources that are connected externally at the ends of the illuminated line. One of the procedures is formulated directly in the phase-domain and is compatible with the universal line model (ULM). The second procedure is formulated in the modal domain and is compatible with the transmission line model proposed by Marti. Both procedures are validated taking as reference a first order FDTD solution of telegrapher's equations considering the presence of external electromagnetic fields. It is shown that the proposed procedures can be efficiently and accurately used for the calculation of lightning-induced voltages on overhead lines.

A Globally Convergent State Observer for Multimachine Power Systems with Lossy Lines

We present the first solution to the problem of estimation of the state of multimachine power systems with lossy transmission lines. We consider the classical three-dimensional “flux-decay” model of the power system and assume that the active and reactive power as well as the rotor angle and excitation voltage at each generator is available for measurement—a scenario that is feasible with current technology. The design of the observer relies on two recent developments proposed by the authors: a parameter estimation based approach to the problem of state estimation and the use of the dynamic regressor extension and mixing technique to estimate these parameters. Thanks to the combination of these techniques it is possible to overcome the problem of lack of persistent excitation that stymies the application of standard observer designs. Simulation results illustrate the performance of the proposed observer.

0IO-Shape PCB Trace Negative Group-Delay Analysis

This paper elaborates a negative group delay (NGD) analysis of 0IO-shape printed circuit board (PCB) traces. This circuit topology is originally implemented with a tri-coupled line (3CL) six-port element with the lateral side connected through lossy transmission lines (TLs). After description of the electrical equivalent diagram, the S-matrix model is established. The group delay (GD) is formulated from the transmission coefficient as a function of the 0IO topological parameters. The effectiveness of the GD modelling is verified with a microstrip circuit proof-of-concept (POC). Simulations and measurements, which are in good agreement, confirm the dual-band bandpass NGD behavior of the 0IO POC. The fabricated prototype generates NGD levels better than -1 ns at NGD center frequencies of about 2.2 GHz and 3 GHz. In addition, to this good NGD performance, the 0IO POC operates with a low insertion loss better than 2.5 dB and reflection losses better than 12 dB in the NGD bandwidths.

A new carbon nanotube-based filter for quantum computing applications

A new article introduces a compact, high-performance lossy transmission line filter based on carbon nanotubes that successfully improves coherence times of a superconducting qubit.

Carbon nanotube-based lossy transmission line filter for superconducting qubit measurements

In superconducting qubit measurements, stray infrared photons lead to damping processes that degrade quantum coherence. In this Letter, we show that a thermal blocking filter made of multiwalled carbon nanotubes diluted in stainless steel powder can significantly improve the energy relaxation time, T1, and the pure dephasing time, Tφ, of a qubit. By using two independent measurement lines, with and without the filter, and switching between them in situ, we observe that with the filter there is an increase of more than 61% in T1 and 291% in Tφ. We characterize the filter, demonstrating that the scattering parameters remain stable down to 8 mK over a wide range of frequencies, spanning from 10 MHz to 50 GHz. We also show that the cutoff frequency of the filter is easily controlled by selecting the concentration of nanotubes.

Nonlinear Membrane Circuit Loaded on a Lossy Transmission Line without the Heaviside’s Condition

The paper deals with transmission lines terminated by a nonlinear circuit describing a simplified model of membrane. This means that all elements of the membrane circuit are nonlinear ones as follows: in series connected LR-loads parallel to C-load. Using the Kirchhoff’s laws we formulate boundary conditions. For lossy transmission lines systems with the Heaviside’s condition, the mixed problem is considered in previous papers. The main goal of the present paper is to investigate the same problem for lossy transmission lines without the Heaviside’s condition. We reduce the existence of solution of the more complicated mixed problem for such a system to the existence of fixed point of an operator acting on a suitable function space. Then by ensuring the existence of this fixed point we obtain conditions for existence of a generalized solution of the mixed problem. The obtained conditions are easily verifiable. We demonstrate the advantages of our method by a numerical example.

Nonlinear Membrane Circuit Loaded on a Lossy Transmission Line without the Heaviside’s Condition

The paper deals with transmission lines terminated by a nonlinear circuit describing a simplified model of membrane. This means that all elements of the membrane circuit are nonlinear ones as follows: in series connected LR-loads parallel to C-load. Using the Kirchhoff’s laws we formulate boundary conditions. For lossy transmission lines systems with the Heaviside’s condition, the mixed problem is considered in previous papers. The main goal of the present paper is to investigate the same problem for lossy transmission lines without the Heaviside’s condition. We reduce the existence of solution of the more complicated mixed problem for such a system to the existence of fixed point of an operator acting on a suitable function space. Then by ensuring the existence of this fixed point we obtain conditions for existence of a generalized solution of the mixed problem. The obtained conditions are easily verifiable. We demonstrate the advantages of our method by a numerical example.

LOSSY TRANSMISSION LINES TERMINATED BY PARALLEL CONNECTED RLC-ELEMENTS WITHOUT THE HEAVISIDE’S CONDITION

The paper deals with analysis of propagation of transverse electromagnetic waves along lossy transmission lines terminated by a circuit consisting of parallel connected RLCelements. Using the Kirchhoff’s laws we derive boundary conditions and formulate the mixed problem for hyperbolic system describing the lossy transmission line. Without the Heaviside's condition, we cannot guarantee the distortionless propagation of waves and hence we cannot apply the known methods. That is why we apply a different method and obtain conditions for existence-uniqueness of generalized solution. We change variables and formulate a mixed problem for the hyperbolic system with respect to the new variables. The nonlinear characteristics of the RLC-elements generate nonlinearity in the equations of neutral type on the boundary. We propose an operator presentation of the mixed problem for transmission line system and by means of fixed point technique we prove existence-uniqueness of a generalized solution.

LOSSY TRANSMISSION LINES TERMINATED BY PARALLEL CONNECTED RLC-ELEMENTS WITHOUT THE HEAVISIDE’S CONDITION

The paper deals with analysis of propagation of transverse electromagnetic waves along lossy transmission lines terminated by a circuit consisting of parallel connected RLCelements. Using the Kirchhoff’s laws we derive boundary conditions and formulate the mixed problem for hyperbolic system describing the lossy transmission line. Without the Heaviside's condition, we cannot guarantee the distortionless propagation of waves and hence we cannot apply the known methods. That is why we apply a different method and obtain conditions for existence-uniqueness of generalized solution. We change variables and formulate a mixed problem for the hyperbolic system with respect to the new variables. The nonlinear characteristics of the RLC-elements generate nonlinearity in the equations of neutral type on the boundary. We propose an operator presentation of the mixed problem for transmission line system and by means of fixed point technique we prove existence-uniqueness of a generalized solution.

Active Electromagnetic Interference Control in Time Domain: Application to Software Correction of Defective Lossy Transmission-Line Networks

This paper introduces a generalized approach of the linear combination of configuration field (LCCF) method. The technique developed in this paper provides a way to identify the temporal profile of electromagnetic sources satisfying particular properties for a given target (fields, voltage, or current). Here, we focus on identifying voltage signals that would lead to a specified voltage over a time interval at some points of a network. To experimentally apply the same idea, we propose two possibilities to decrease the maximum frequencies of the voltage signals. The LCCF method is then applied to bring a software correction to a lossy transmission-line network presenting soft or hard defects.

Research and validation of design principles for PVDF wideband ultrasonic transducers based on an equivalent circuit model

With the increasing use of ultrasonic measurement technology in many fields, the demand for the wideband ultrasonic transducers is also growing. In order to design a wideband piezoelectric ultrasonic transducer, the design principles of wideband PVDF piezoelectric ultrasonic transducers are studied in this paper. A new equivalent circuit model of piezoelectric ultrasonic transducer is used here to simulate the piezoelectric ultrasonic transducer, which combines with the controlled source model and the lossy transmission line model. Based on this model, the relationships between physical structures and properties of PVDF transducers are studied both in simulation and experiment. It shows that the center frequency and many other property parameters of PVDF ultrasonic transducers are strongly related to the physical structures of it. Finally, a wideband PVDF piezoelectric ultrasonic transducer is produced with the center frequency of about 5.3 MHz ± 0.1 MHz and the bandwidth of more than 90%.

Analytical studies on waves in nonlinear transmission line media

In this study, we introduce the lossy nonlinear transmission line equation, which is the dissipative-dispersive equation and an important problem of electrical transmission lines. For the engineers and physicist, the equation and its exact solutions are important so to obtain the exact solutions; one of the modifications of auxiliary equation method based on Chebyshev differential equation is studied. The results are discussed and given in details. Recently, the studies of lossy transmission line equation have been challenging, thus, it is believed that the proposed solutions will be key part of further studies for waves in nonlinear transmission line media, which has mixed dissipative-dispersive behavior.