Lossy Transmission Line Model Research Articles

Analysis of the Voltage Distribution in a Motor Stator Winding Subjected to Steep-Fronted Surge Voltages by Means of a Multiconductor Lossy Transmission Line Model

In this paper, the effect of steep-fronted voltage waveshapes infringing on a pulse-width-modulated (PWM) inverter fed induction motor is studied. The system, composed of a feeder cable and a stator winding, is modeled and simulated by using multiconductor transmission line theory in order to predict the voltage distribution among the coils of the stator winding. A recently developed time-domain equivalent circuit is used; it allows one to correctly describe the dielectric losses and the skin-effect in the conductors. The relationship among the voltage distribution inside the electrical insulation and parameters like the rise time of the applied voltage, the cable length, and the distributed losses is deeply discussed. Good agreement has been found among experimental and numerical results.

Analysis of a printed CPW-fed slot antenna using a lossy transmission-line model

A model of the printed CPW-fed slot antenna based on the lossy transmission-line method is presented. An original field distribution inside the slots is proposed to compute the input impedance of CPW-fed radiating slot antennas. The theoretical and experimental results are compared successfully in the X-band for radiating slots printed on low- and high-permittivity substrate. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 45–48, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20542

Accurate non-uniform transmission line model and its application to the de-embedding of on-wafer measurements

An accurate model for lossy non-uniform transmission lines is presented. The technique provides a coplanar waveguide (CPW) taper model, which has been used to accurately de-embed measurements of passive CPW components in line geometries differing from the nominal 50/spl Omega/ geometry of the calibration. The model accounts for both dielectric and conductor losses, and is shown to be in excellent agreement with measured results from 45 MHz to 120 GHz.

Inversion MOS capacitance extraction for high-leakage dielectrics using a transmission line equivalent circuit

Accurate measurement of MOS transistor inversion capacitance with a physical silicon dioxide thickness less than 20 /spl Aring/ requires correction for the direct tunneling leakage. This work presents a capacitance model and extraction based on the application of a lossy transmission line model to the MOS transistor. This approach properly accounts for the leakage current distribution along the channel and produces a gate length dependent correction factor for the measured capacitance that overcomes discrepancies produced through use of previously reported discrete element based models. An extraction technique is presented to determine the oxide's tunneling and channel resistance of the transmission line equivalent circuit. This model is confirmed by producing consistent C/sub 0x/ measurements for several different gate lengths with physical silicon dioxide thickness of 9, 12, and 18 /spl Aring/.

DC-110-GHz MMIC traveling-wave switch

This paper presents the broadest band monolithic-microwave integrated-circuit traveling-wave switch ever reported for millimeter-wave applications. The developed switch with the novel structure of a 400-/spl mu/m-gate finger field-effect transistor (FET) indicated an insertion loss of less than 2.55 dB and an isolation of better than 22.2 dB from dc to 110 GHz. Also, the switch indicated no degradation of insertion loss and an ON/OFF ratio of more than 22.7 dB up to an input power of 26.5 dBm at 40 GHz. Circuit analytical results based on a lossy transmission-line model for small-signal performance and circuit simulation results using the two-terminal nonlinear FET model for large-signal operation successfully showed good agreement with the experimental results.

Lossy transmission line model of hydrofractured well dynamics

The real-time detection of hydrofracture growth is crucial to the successful operation of water, CO 2 or steam injection wells in low-permeability reservoirs and to the prevention of subsidence and well failure. In this paper, we describe propagation of very low frequency (1–10 to 100 Hz) Stoneley waves in a fluid-filled wellbore and their interactions with the fundamental wave mode in a vertical hydrofracture. We demonstrate that Stoneley-wave loses energy to the fracture and the energy transfer from the wellbore to the fracture opening is most efficient in soft rocks. We conclude that placing the wave source and receivers beneath the injection packer provides the most efficient means of hydrofracture monitoring. We then present the lossy transmission line model of wellbore and fracture for the detection and characterization of fracture state and volume. We show that this model captures the wellbore and fracture geometry, the physical properties of injected fluid and the wellbore-fracture system dynamics. The model is then compared with experimentally measured well responses. The simulated responses are in good agreement with published experimental data from several water injection wells with depths ranging from 1000 ft to 9000 ft. Hence, we conclude that the transmission line model of water injectors adequately captures wellbore and fracture dynamics. Using an extensive data set for the South Belridge Diatomite waterfloods, we demonstrate that even for very shallow wells the fracture size and state can be adequately recognized at wellhead. Finally, we simulate the effects of hydrofracture extension on the transient response to a pulse signal generated at wellhead. We show that hydrofracture extensions can indeed be detected by monitoring the wellhead pressure at sufficiently low frequencies.

Calculation of inductive coupling from power lines to multiple pipelines and buried conductors

A method for calculation of currents and voltages in the system of parallel pipelines and buried conductors is proposed. The method is based on the lossy transmission line model for buried conductors and previous methods based on the same approach are modified by abandoning the Thevenin circuit representation of pipeline sections and by deriving a 4-pole equivalent II circuit of a pipeline section. A generalized matrix 4-pole equivalent circuit is derived for a system of parallel buried conductors as well, by using the modal method. A general case of buried conductors not parallel to the power line is also derived.

MODELING OF VLSI INTERCONNECT

Digital systems utilize frequencies into the GHz range Attempts to reduce the propagation delay by lowering the interconnect capacitance (decreasing cross‐sectional dimensions) cause an increase in wire resistance which, in turn, increases the rise time and indirectly slows down the response Therefore, it is impossible to optimize VLSI and packaging interconnections to maximize the clock rate without analyzing losses (solving Helmholtz equation) and implementing lossy transmission line models This paper presents modeling and simulation of a gate array interconnect.

A universal model for lossy and dispersive transmission lines for time domain CAD of circuits

Branin's method of characteristics has been extended to obtain a universal equivalent model for lossy and dispersive transmission lines. Existing CAD software packages, such as SPICE, can be used for this implementation. The starting point for obtaining the model is the analog filters that approximate the characteristic impedance Z/sub 0/(s) and the propagation function F(s)=exp(- gamma l) of the transmission line. The circuits are synthesized using conventional network synthesis techniques. An examination of the validity of the model is carried out by analyzing an example of RLCG lines driven by bipolar logic gates and the distortion of a DC Gaussian pulse as it propagates along a microstrip line. >

Transient analysis of lossy transmission lines with arbitrary initial potential and current distributions

The method of characteristics has been generalized for the transient analysis of lossy transmission lines with arbitrary initial conditions. It is shown that traveling waves generated by the initial potential and current distributions can be simulated by voltage and current generators connecting to the terminals of the lossy transmission-line model consisting of ideal delay-lines and waveshaping networks synthesized by the modified Pade approximation. The discrete-time transient simulation requires neither the FFT nor convolution integral and is as efficient as the iterative waveform relaxation technique. Transient responses of lossy transmission lines with steady-state and transient initial potential and current distributions are simulated for illustration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of printed linear slot antenna using lossy transmission line model

A model of the printed linear slot antenna using the lossy transmission line method is presented. The Cohn analysis is used to determine the characteristics of the slotline. The attenuation coefficient is numerically determined. Theoretical input impedances of offset-fed slots are compared successfully with experimental results given by other authors.

An enhanced time-domain approach for dielectric characterization using stripline geometry

A time-domain approach for dielectric characterization using a stripline geometry is presented. The technique uses both time domain reflectometry (TDR) and time domain transmission (TDT) measurements for determining an optimum frequency-dependent lossy transmission line model for the stripline under test. The optimization is done in the time domain by comparing the experimental TDR and TDT response waveforms with the simulated ones using a nonlinear least squares fit. The material properties such as the complex permittivity of the dielectric material are determined from the optimum lossy transmission line model. The authors present both simulated and experimental results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A new time-domain approach for determining the complex permittivity using stripline geometry

A time-domain approach for determining the complex permittivity of materials using stripline geometry is presented. The technique uses time-domain reflectometry (TDR) measurements and computer simulation to determine an optimum lossy transmission-line model characterizing the stripline under test. The line model is then used for determining the complex permittivity of the dielectric material. The validity of the technique is demonstrated by using a stripline constructed from Rogers RT/Duroid composite laminate and one constructed from thick-film paste. Accurate estimates for both the Duroid's and the thick film paste's dielectric constant were obtained. The technique is incapable of determining the loss tangent if the mismatch between the step generator and the stripline under test is very high and the loss tangent is fairly small.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Anomalous RF induced steps in resonant Josephson tunnel junctions for voltage standard maintenance

The authors theoretically investigated the current steps in the I-V (current-voltage) characteristics of a long Josephson tunnel junction driven by microwaves at frequencies near its geometrical resonance. They used a numerical algorithm based on a lossy transmission line model of the Josephson tunnel junction to calculate the DC current density distribution. In addition to the fundamental microwave frequency, harmonic contents of the tunneling current are also considered. The calculations show a strong asymmetric behavior of the current steps with respect to the quasi-particle curve. It is suggested that the excitation of higher harmonic waves gives rise to these anomalous microwave-induced steps. Due to the nonuniform DC-tunneling-current density distribution, the amplitudes of these current steps are not usually larger than 10% of the critical current. Since the critical current in long junctions is of the order of milliamperes, these amplitudes are considered relatively large. >

SPICE implementation of lossy transmission line and Schottky diode models

The author describes models for the lossy transmission line and the Schottky diode that are incorporated into the source code of the circuit simulation program SPICE (version 2G.6). The model used for the lossy transmission line was derived by A.J. Gruodis (1979). The DC model for the Schottky barrier diode as shown was formulated by D.B. Estreich (1983). Examples used to verify the models are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Linear transmission-line model analysis of arbitrary-shape patch antennas

A quasi-TEM lossy transmission-line model is used to express the radiation admittance of an arbitrary-shape symmetrical patch antenna which is linearly polarised. The then retical admittance is obtained from the solution of a Riccati differential general equation.

Influence of feed-point location on radiation resistance of a short-circuited flat dipole

A quasi TEM lossy transmission line model is used to calculate the effect on the radiation resistance which is produced by moving the feed-point location along a short-circuited flat dipole acting at quarter-wave resonance. Very good agreement is obtained between theoretical and experimental results.