Transmission Line Matrix Research Articles

Sound propagation modeling in forests using the transmission line matrix method: Comparison with experimental in situ measurements

We present efforts to adapt the time-domain Transmission Line Matrix (TLM) method for modeling sound propagation in forests. It is relevant to professionals and researchers in environmental acoustics and to those interested in studying sound propagation in outdoor environments using numerical modeling techniques. The study aims to demonstrate the applicability of the method in complex media where sound waves undergo multiple reflections combined with ground effects during their propagation from a sound source to a receiver point. The TLM method is used to numerically model sound propagation in a 3D forest geometry generated based on a real tree distribution case. Data from an experimental campaign conducted in the rainforest of French Guyana are used as a reference. The results show an encouraging comparison between them and the in situ measurements, even if the hypotheses made to adapt the input data in the model were strong. We find that more measurement points and more specifications (ground impedance measurements, canopy density, etc.) about the experimental site are needed for further simulations, even if obtaining them presents technical difficulties.

Quasi-3D Model for Lateral Resonances on Homogeneous BAW Resonators.

Lateral modes are responsible for the in-band spurious resonances that appear on BAW resonators, degrading the in-band filter response. In this work, a fast computational method based on the transmission line matrix (TLM) method is employed to model the lateral resonances of BAW resonators. Using the precomputed dispersion curves of Lamb waves and an equivalent characteristic impedance for the TE1 mode, a network of transmission lines is used to calculate the magnitude of field distributions on the electrodes. These characteristics are specific to the stack layer configuration. The model's implementation is based on nodal Y matrices, from which particle displacement profiles are coupled to the electric domain via piezoelectric constitutive relations. Consequently, the input impedance of the resonator is obtained. The model exhibits strong agreement with FEM simulations of FBARs and SMRs, and with measurements of several SMRs. The proposed model can provide accurate predictions of resonator input impedance, which is around 200 times faster than conventional FEM.

TEM-камера открытого исполнения для испытаний малогабаритных радиоэлектронных средств на электромагнитную совместимость

This paper presents the design and fabrication of an open TEM cell. It allows you to measure the radiated emission and immunity of radioelectronic devices. The size of the EUT should not exceed 184×162×30 mm. Performed analytical and quasi-static analysis of the regular part of the TEM cell. In the frequency range up to 1.4 GHz the reflection coefficient |S11| of the regular part does not exceed minus 45 dB. The electrodynamic model of the TEM cell is developed and the geometric parameters are optimized using a genetic algorithm. Analysis of the electrodynamic model showed that in the frequency range up to 920 MHz the voltage standing wave ratio (VSWR) does not exceed 1.3. The inequality of the electric field in the area of EUT placement is not more than 6 dB in the frequency range up to 875 MHz. The validity of the obtained results is checked using the numerical methods of finite elements and the transmission line matrix. A solid-state model of the TEM cell is developed to evaluate the effect of the design features of the assembly. The frequency dependences of |S11| of the solid‑state model do not exceed minus 17.69 dB in the frequency range up to 916 MHz. The TEM cell is fabricated by laser cutting and bending aluminum sheet metal. Using a vector circuit analyzer Micran R4M-18 measured S‑parameters of the fabricated TEM cell. The transmission coefficient |S21| of the fabricated TEM cell in the frequency range up to 936 MHz does not exceed minus 2.2 dB. The reflection coefficient |S11| does not exceed minus 17.69 dB. The results of radiated emission measurements of the Altera Cyclone IV FPGA debug board in the frequency range up to 1 GHz with a fabricated TEM cell is presented.

Transmission Line Matrix Model: Numerical Dispersion Effects on Simulated Specular Reflection

Transmission Line Matrix Model: Numerical Dispersion Effects on Simulated Specular Reflection

A New Method for Twisted Wire Crosstalk Estimation Based on GA-BP Neural Network Algorithm

Based on the research of genetic algorithm (GA) to optimize the BP neural network algorithm, this paper proposes a method for predicting twisted wire crosstalk based on the algorithm. Firstly, the equivalent circuit model of a multi-conductor transmission line is established, combined with the method of similarity transformation, the second-order differential transmission line equations are decoupled into n groups of independent two-conductor transmission line equations, and the crosstalk is finally solved. Then the mathematical model of the twisted wire is established and its structural characteristics are analyzed, and the GA-BP neural network algorithm is used to realize the mapping of the electromagnetic parameter matrix of the twisted wire and the position of the twisted wire. Finally, the mapping relationship is substituted into the transmission line equation, and the near-end crosstalk (NEXT) and the far-end crosstalk (FEXT) of an example three-core twisted wire are predicted based on the idea of cascade combined. By comparing with the transmission line matrix method (TLM), it can be seen that the method proposed in this paper is in good agreement with the crosstalk results obtained by the electromagnetic field numerical method, which verifies the effectiveness of the algorithm proposed in this paper.

ISM 2.4 GHz Band Antenna Model for RF Energy Harvesting Systems

In today’s world many technological devices can operate with very low power levels. Despite this situation, these devices need to be fed with a sustainable energy source and constantly charged. This low level power need can be attained from ambient electromagnetic waves from any radio frequency sources. Radio frequency energy harvesting systems can be offered to feed these type of devices and these systems have been used in many areas in recent years. In this study, an antenna designment that can be used in RF energy harvesting systems is emphasized. Within the scope of this study, an RF energy harvesting antenna operating at 2.4 GHz frequency has been modeled. The electromagnetic performance and antenna fundamental parameters of the RF energy harvesting antenna are numerically calculated using a commercial 3D based on a transmission line matrix (TLM) and the finite integration technique (FIT). The physical extents of the antenna are 35 x 28 x 1.6 mm. The proposed RF energy harvesting antenna has 2.1 dBi directivty and %98.1 radiation efficiency performance parameters. The antenna proposed here can be have usage areas such as an RF energy harvesting antenna for low-power medical devices, self sustainable wireless devices in Internet of Things (IoT), Wireless Body Sensor Network (WBSN) devices.

Advanced impedance modeling for micropatterned polymer electrolyte membrane fuel cells

Cathode patterning is an effective means of improving the oxygen reduction reaction in polymer electrolyte membrane fuel cells. Because the conventional one-dimensional transmission line model cannot be applied to micropatterned electrodes, impedance modeling for micropatterned electrodes is conducted using a two-dimensional transmission line matrix model. In this study, the charge transfer resistance is considered a function of proton potential in the equivalent circuit based on the Butler–Volmer equation. Micropatterned membrane electrode assemblies (MEAs) with three different pattern depths are fabricated, and electrochemical measurements are performed on them. The measured and simulated impedances are evaluated using the distribution of relaxation times analysis results. This study validates the proposed model by comparing the simulated and measured impedances of the MEAs. The experimental and matrix model simulation results confirm that cathode patterning reduces both the charge transfer and proton conduction resistances. For each MEA, the charge transfer resistances obtained by fitting the matrix model to the measured impedances are plotted on a straight line; thus, the Tafel slope is obtained. The matrix model demonstrated in this study leads to the design of patterned electrodes through the impedance analysis of various patterned electrodes.

Application to Real Power Networks of a Method to Locate Partial Discharges Based On Electromagnetic Time Reversal

The paper presents an experimental validation of a method to locate partial discharges (PDs) on power distribution and transmission networks. The method is based on electromagnetic time reversal (EMTR) theory, and it uses a Transmission Line Matrix (TLM) model to describe the propagation of the PD signals in the reversed time. Since PDs are regarded as a symptom of insulation degradation, on-line PD location is considered an important approach to monitoring the integrity of a power distribution network, with the aim of detecting and preventing faults and improving network reliability. In this paper, the EMTR-based method is described and its effectiveness in PD localization using only one measurement point is demonstrated in three real 33 kV power lines. Its effectiveness is proved with and without an on-line electromagnetically noisy environment, and its accuracy is evaluated with respect to different signal-to-noise ratio (SNR) levels of the networks. The validation shows that the method is able to locate PDs with an error of 0.14% with respect to the total length of the line in the absence of noise, and with an error that is always lower than 0.5% for an SNR down to −7 dB.

On-Line Partial Discharge Localization in Power Cables Based on Electromagnetic Time Reversal Theory - Numerical Validation

This paper presents the numerical validation of a new on-line location method of partial discharge (PD) in cables of Medium Voltage (MV) power networks based on the electromagnetic time reversal (EMTR) theory. Because PD events are a symptom of cable insulation degradation, PDs localization is a key topic for fault prevention on power networks, increasing their reliability and resilience and to guaranteeing electricity security. A description of the proposed EMTR PD location method is given and its effectiveness and accuracy are analyzed in lines with both homogeneous and inhomogeneous power cables. The accuracy of PD location methods is strongly affected by the distortion of the PD pulses during their propagation on power lines, caused mainly by the skin effect. For this reason, the accuracy of the proposed location method is analyzed using a lossy model of power networks that is able to reproduce PD signals distortion. The model used, realized using the transmission line matrix (TLM) method, is also presented here and theoretically validated.

A model for the prediction of the shielding effectiveness of cylindrical enclosure

This paper presents a model to predict the shielding effectiveness (SE) and resonant modes of cylindrical enclosure with apertures or dielectric substrate. In this model, the Robinson equivalent circuit model (RECM) is introduced to deal with aperture impedance, and the extended form of the Baum–Liu–Tesche equation is deduced to calculate the induced voltage in the enclosure. The electromagnetic topology (EMT) model is established to analyze the process of energy transmission inside the enclosure. The energy propagation coefficient matrix and the scattering coefficient matrix are calculated to deal with the SE results of the observation point. To quantify the efficiency of the proposed model, the calculation results are compared with the full-wave transmission line matrix method (TLM) and RECM through the Fréchet distance. The comparison results show that the accuracy of the proposed model is better over a wide frequency range compared with RECM, and meanwhile, it consumes less run time and fewer CPU resources than traditional numerical methods. The validity of the presented model is verified by TLM.

Lightning the Electromagnetic Pulse Coupling of Airborne Secondary Radar Electronic Equipment Using Intelligent Computing

In order to analyze the lightning coupling of the airborne secondary radar electronic equipment, this study analyzes the transient electromagnetic field strength of the airborne secondary radar electronic equipment and the current density distribution on the aircraft surface when the lightning directly hits the aircraft based on the simulation technology of the transmission-line matrix method. On this basis, the simulation research of field distribution and cable coupling is further carried out. Through the simulation calculation, it can be seen that when the lightning strikes the aircraft, the current density is relatively small in the continuous parts of the upper and lower surfaces of the fuselage and the middle of the wing. In addition to the areas where the lightning current is easily attached, structural irregularities such as windows, engines, front and rear edges of wings, and outboard antennas are often affected by edge effects, and the current density is often concentrated, requiring key protection. For more sensitive electronic equipment, the cable connected to it can be considered to use an appropriate type of shielded cable to achieve the shielding effect on the electromagnetic environment.

DETERMINATION OF THE TRANSMISSION LINE RESISTANCE MATRIX WITH DEVIATIONS OF DESIGN PARAMETERS FROM NOMINAL

Context. UHF transmission systems make extensive use of transmission line segments, the characteristics of which have a significant impact on the performance of various information technologies. One of the problems of production of transmission lines is to obtain a given wave impedance, which significantly affects the electrical and information characteristics of the entire set of equipment. Currently, there is a burning issue of estimating the influence of disturbing factors on various electrical characteristics of long line segments. To date, the most fully developed methods for assessing the effect of disturbing factors on the wave impedance of a homogeneous line (the wave impedance is constant) under regular perturbations. In this case, the influence of perturbations on the reflection coefficient of matched lines was mainly considered. The effect of perturbations on the other characteristics of homogeneous and, especially, inhomogeneous lines has not been sufficiently studie
 Objective. The purpose of this paper is to determine the effect of wave impedance perturbations on the transmission line impedance matrix. Knowing the perturbed impedance matrix, it is possible to determine the distortion of the characteristics of any device built on transmission line segments. 
 Method. The paper uses the method of perturbation theory of linear differential operators applied to equations describing processes in inhomogeneous long lines.
 Results. The obtained results make it possible to estimate the influence of regular and irregular perturbations of the wave resistance (wave conductance) on the transmission line matrix considered as a quadrupole. Such matrix can be any quadrupole matrix: resistance matrix, conductance matrix, circuit matrix. This makes it possible, according to the desired function of the circuit (gain, input impedance, reflection coefficient), to determine the allowable deviation of the wave impedance from the nominal value in order to select a tolerance for reproducing the wave impedance. 
 Conclusions. The proposed criterion for estimating line parameter deviations using the norm of the four-pole matrix is inherently an integral criterion and can be used to preliminarily estimate the frequency domain of the strongest distortions, regardless of the functional purpose of the transmission line segment. The developed approach is applicable to both homogeneous and heterogeneous transmission lines and covers both regular and irregular wave impedance perturbations.

Study of the substrate surface treatment of flexible polypyrrole-silver composite films on EMI shielding effectiveness: theoretical and experimental investigation

Abstract Conductive flexible polypyrrole-silver (PPy-Ag) composite films were prepared on Biaxial Oriented Polyethylene Terephthalate (BOPET) substrate with surfaces treated by (3-aminopropyl) trimethoxysilane (APTMS). The surface treatment was carried out to improve the adhesion, morphology, and electrical properties of the deposited film to enhance the Electromagnetic Interference Shielding Effectiveness (EMI-SE). APTMS grafting on the BOPET substrate was confirmed by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) analyses. All structural, morphological, and electrical features of PPy-Ag raised from different AgNO3 molar ratio were investigated. The shielding effectiveness properties, experimentally determined for the synthesized PPy-Ag films were compared to those simulated analytically and numerically based on the transmission line matrix method (TLM). Both analytical and numerical models showed a good agreement with experimental measurements. The obtained results confirmed that the PPy-Ag films of 0.5 M/1 M molar ratio exhibits high EMI shielding performance of about 21 dB along with an electrical conductivity of 47 S/cm. Therefore, the treated surface flexible PPy-Ag films can be considered as potential candidate for high frequency electromagnetic interference shielding applications.

Analysis of the numerical properties of the transmission line matrix model for outdoor sound propagation

Outdoor sound propagation modeling can be performed through various numerical models. Nowadays, time-domain methods are widely used and enable accurate simulations for most of the sound physical phenomena involved in environmental acoustics. However, the transmission line matrix (TLM) method remains relatively poorly documented. In this paper, a thorough review of the method and a stability analysis are provided. The review of the model leads to a more robust understanding of its link with the wave equation using Taylor expansions. Two different cases are considered: a homogeneous non-dissipative medium and an inhomogeneous dissipative one. The stability analysis shows the quantification of the model inherent dispersion error and highlights similarities with a finite difference scheme. To conclude, a numerical experiment aims to characterize precisely the limitations of the method applied to outdoor sound propagation.

Simulation and Experimental Study of the Field Distribution of Engine for Electromagnetic Pulse

The protection of electromagnetic pulse (EMP) is important for aircraft due to vulnerable electronic equipments are installed. The control box of engine is also suffering from EMP and seldom studied. Meanwhile, most of work related to EMP protection focus on shielding design. Few works consider the effect of engine shell. The field distribution induced by EMP and its influences on the controller layout are unaddressed. This work will comprehensively investigate the field distribution characteristics of an engine under EMP, which is studied by simulating and experimenting methods. The transmission line matrix (TLM) is used to simulated field distribution of the bounded wave simulator and aero-engine, which provides better placement for equipment under test in the simulator. The field differences of bounded wave simulator and plane wave have been analyzed by using CST software. The feasibility of plane excitation instead of bounded wave simulator model excitation is checked, which has been verified by using the engine model. Then, the distribution characteristics of transverse and longitudinal fields surrounding the aero-engine are obtained, and the surface current distribution of the engine is also obtained in the simulation. The aero-engine simulation is excited by bounded wave simulator under CST software. According to the corresponding monitoring points, the simulated field distribution characteristics are verified by using the largely bounded wave simulator. Finally, the influence of field distribution on the layout of the engine electronic control system is analyzed, which provides a reference for the anti-electromagnetic pulse design of the engine electromagnetic controller.

The Effect of the Ring Mains Units for On-Line Partial Discharge Location With Time Reversal in Medium Voltage Networks

The performance of a new on-line partial discharge (PD) location method based on the Electromagnetic Time Reversal (EMTR) theory and the Transmission Line Matrix (TLM) method are investigated for characterization of Medium-Voltage (MV) networks. The distortion of the PD signal during its propagation along a cable connection including network components modelled based on experimental data is reproduced in simulation and the effectiveness of the EMTR-based method to localize the PD source is analyzed. In particular, the effects of the ring main units (RMUs), that behave as a complex impedance, the variation with frequency of the MV cable impedance and the reflection patterns, due to impedance mismatches, are considered and investigated. Simulation results are given showing the performance of the EMTR method in two different networks configurations: the former one with a RMU at the end of a MV cable and the latter one with a second MV cable connected to the RMU of the first configuration having a distribution transformer at its far end. The results show that the EMTR method is able, with only a single observation point, to localize PDs also in the presence of RMU with a relative error, with respect to the line length, of approximately 1%.

Dispersion and Stability Analysis for TLM Unstructured Block Meshing

The insatiable demand to optimize and engineer new functionalities in electromagnetic devices has risen their geometrical complexity to unprecedented levels. This usually results in computationally multiscale problems with some tiny components of great importance to the overall behavior of these devices. Block meshing is a powerful technique for treating such problems. The usage of variable mesh size is adaptable for adequately representing the geometrical details without exhausting the computational resources with a uniform fine grid in the entire computational domain. In addition, block meshing allows the use of cubic cells only for which time step in maximum and velocity error is minimal in each subregion. In this article, we present a mathematical formulation for stability and dispersion analysis when using block meshing in the transmission-line matrix (TLM) method. These relations permit us to compute the maximum mesh size and time step that guarantee a tolerable level of numerical dispersion, hence minimizing the computational expenditures. Moreover, we study the case of adopting the local time step and demonstrate the origins of the instability that may appear in this case. Finally, some numerical experiments are presented to show the advantages of the proposed approach when using TLM block meshing. A similar procedure can be used for FDTD or FIT with block meshing.

A New Approach to the Modeling of Anisotropic Media with the Transmission Line Matrix Method

A reformulation of the Transmission Line Matrix (TLM) method is presented to model non-dispersive anisotropic media. Two TLM-based solutions to solve this problem can already be found in the literature, each one with an interesting feature. One can be considered a more conceptual approach, close to the TLM fundamentals, which identifies each TLM in Maxwell’s equations with a specific line. But this simplicity is achieved at the expense of an increase in the memory storage requirements of a general situation. The second existing solution is a more powerful and general formulation that avoids this increase in memory storage. However, it is based on signal processing techniques and considerably deviates from the original TLM method, which may complicate its dissemination in the scientific community. The reformulation presented in this work exploits the benefits of both methods. On the one hand, it maintains the direct and conceptual approach of the original TLM, which may help to better understand it, allowing for its future use and improvement by other authors. On the other hand, the proposal includes an optimized treatment of the signals stored at the stub lines in order to limit the requirement of memory storage to only one accumulative term per field component, as in the original TLM versions used for isotropic media. The good behavior of the proposed algorithm when applied to anisotropic media is shown by its application to different situations involving diagonal and off-diagonal tensor properties.

Simulation for a Crosstalk Canceling Algorithm in Lossless Multiconductor Transmission Lines

This letter presents an algorithm for canceling crosstalk in multiconductor transmission lines (MTL). At present, to reduce the crosstalk, multiconductor systems usually use differential mode transport, in which the number of transmitted signals is half the number of conductors. A method is proposed to cancel crosstalk in MTL, through the singular value decomposition (SVD) method in matrix theory, in which the transmission line matrix is converted into an identity matrix. That is, the off-diagonal elements in the transmission matrix are zero, which corresponds to crosstalk cancellation. In this letter, this method is applied to the previous literature models to verify its effectiveness firstly. Then, the method is applied to a triple-twisted strand. In the strand, different rotation degrees correspond to different per unit length (p.u.l) parameter matrix. A set of parameters are extracted, the rest of are predicted by the beetle antennae search-back propagation neural network (BAS-BPNN) proposed in a previous work. The simulation results show that the near and far end crosstalk can be canceled effectively.

Simulation of pulsed ultrasonic diffraction in viscous fluids using transmission line matrix method.

Ultrasonic fields propagating in viscous media undergo changes in shape due to diffraction, attenuation, and dispersion. Until now, some implementations in the transmission line matrix (TLM) method has been developed to simulate either diffraction or attenuation but never both. In this work, the quadratic frequency dependence of the absorption coefficient as well as the dispersive effect of a viscous fluid are introduced in the TLM method. The idea is to decompose the emitted wave into its components at different frequencies using Fourier transform. Then, dispersion and attenuation effects are considered for each wave component separately before superposing them to get the required acoustic response. This is possible because each one of them is characterized by a constant absorption coefficient and propagates at a single speed. This TLM model has been applied to the diffracted ultrasonic field by a circular transducer radiating a short pulse in a viscous fluid. The obtained waveforms are interpreted in terms of plane and edge waves. A study of the influence of the most important parameters on the waveform of the detected ultrasonic pulses is performed. The numerical results obtained highlight the attenuation effect on the waves' shapes and the influence of the dispersion on their arrival times.