Transmission Line Segments Research Articles

A novel wall parameter estimation approach based on transmission line method from through-wall radar measurements

A novel technique for estimation of the wall’s relative permittivity, thickness and conductivity from signals measured from the through-wall radar is presented in this paper. The retrieval process is built around an electromagnetic circuit model that represents the wall structure as a transmission line segment. The propagation of the radar signal through the wall is equivalently described as a pair of voltage and current waves that propagate along the transmission line, using analogies between the electrical parameters of the transmission line segment and the constituent parameters of the materials of the wall structure. The synthetic time domain signal obtained analytically and the real through wall imaging time domain signal were correlated to estimate the wall parameters of the layers that comprise the wall structure. The effectiveness of the proposed estimation technique has been demonstrated through simulation and experimentation on two actual building walls. A comparison with conventional methods revealed consistent results between the estimated wall parameters using the proposed technique and those obtained through traditional approaches. These findings highlight the potential of the proposed method in enhancing the accuracy of real-time target localization and tracking in through-wall imaging applications.

Distributed-Source Transmission Line Theory for Modeling the Coast Effect on Geoelectric Fields

Geomagnetic effects on man-made ground-based systems are an increasing concern such as power grids, submarine cables, pipelines, and railway systems. Assessing the threat to these systems requires calculating the geoelectric field induced at the Earth's surface during geomagnetic disturbances and using this as input to a system model to determine the electric currents flowing across the system. Calculations of the geoelectric fields need to take account of lateral variations in conductivity that can affect the geoelectric field at and near discontinuities such as the coast. This paper presents a new method for modeling the influence of coast effect on geoelectric fields based on a generalized thin sheet model but develops a solution derived from distributed-source transmission line theory. Transmission line segments are converted to equivalent-pi circuits which are held together to compose a nodal admittance network representing the Earth's surface and underlying crust. Inversion of the admittance matrix combined with magnetic source fields then determine the geoelectric field profile across the coast. Two cases are presented to show how the DSTL theory is applied to different Earth conductivity models. Calculation results are compared with numerical solutions obtained from FEM, which confirms the accuracy of the DSTL theory for computing geoelectric fields.

Ensuring the performance of modified microstrip loops in the frequency band

Problem statement. Microstrip loop structures of various configurations are widely used to form topologies of multi-pole microwave devices. In this regard, there is a need to study the frequency properties and topological features of the construction of loop structures that determine the amplitude and phase frequency characteristics, as well as the overall parameters of a microstrip radio engineering device. Objective. Studying of frequency characteristics of T- and U-shaped loop configurations implemented on the basis of high-resistance and low-resistance segments of microstrip transmission lines that allow configuring small-sized topologies of multi-pole devices with acceptable electrical characteristics. Results. A number of basic topologies of loop structures designed to function in given frequency bands have been studied. With the help of electrodynamic modeling and parametric optimization, according to a number of criteria (given wave resistance, phase shift, reflection coefficient), the necessary geometric dimensions of the modified topologies were determined. The dependence of the frequency band on the geometric dimensions of the low-resistance loop of the T-section is revealed. By the level of “minus” 20 dB from the maximum of the reflection coefficient, the values of the frequency band width of two types of T-structures – symmetrical and counter-pin - were determined and compared. It is shown that the U-shaped section is characterized by an increased frequency band due to better matching, however, its geometric dimensions exceed the dimensions of the basic T-structures. Practical significance. Modified microstrip loop structures in some cases are able to effectively replace quarter-wave segments of transmission lines, on the basis of which most microwave devices are formed (directional couplers, power dividers, electric filters, phase shifters, crossovers, etc.). The use of combinations of T- and U-shaped structures leads to a significant reduction in the area of microstrip devices designed to operate in the UHF and Microwave bands.

Multi-hazard assessment of transmission line systems subjected to independent non-concurrent turbulent winds and ground accelerations

The design of transmission lines is based on the Load and Resistance Factor Design approach, considering that their collapse limit state is governed by climatic actions (wind and ice). Even so, accident reports indicate the regular observation of moderate to severe damage of towers after strong ground motions, affecting the structure’s capacity to withstand future load events. Therefore, integrating the concepts of Performance-Based and Multi-Hazard Design, successfully applied to buildings and still embryonic to transmission lines, seems to be promising. With such performance-based multi-hazard approaches, intermediate performances can be evaluated even when they are controlled by a non-dominant hazard. Hence, the present paper aims at performing an original multi-hazard assessment of a Chilean 230kV transmission line segment. For this purpose, direct geometric and material nonlinear time history analysis, using a finite element suitable for eccentrically loaded angle profiles (L-shaped cross-sections), is employed to construct the fragility curves. In addition, uncertainties in loads and material properties are accounted for to address the transmission line system failure probability. In the existing literature, fragility analysis has been performed through pushover approaches, whereas reliability has been assessed for a single structure rather than for the transmission line system, as recommended by line codes. Contrary to design practice, the results show that seismic loads control all limit states in TLs located from central to northern Chile. Numerical results presented in this paper are based on 5000 h of total computation time.

Design of Microstrip Transversal Signal-Interference Circuit With Large Group Delay

This letter presents the group-delay (GD) analysis and design of a microwave stub-loaded structure. This circuit can be designed using transversal signal-interference (TSI) principles, which were previously applied to realize sharp-rejection microwave filters with transmission zeros (TZs) through constructive/destructive signal-interaction effects. The engineered circuit topology consists of a bi-path in-parallel transmission-line (TL) filtering stage loaded with an open-ended TL segment or stub at one of its electrical paths. This type of circuit exploits the spectral phase-slope variation of its transfer function, which is caused by modifying the frequency spacing between the two created notched bands or TZs below/above its main passband to generate a large GD within it. A microstrip prototype of the devised TSI-based GD circuit is built and tested for experimental-validation purposes. It exhibits among the highest GD of 10.3 ns at its operational frequency of 1 GHz compared to prior-art large-GD structures reviewed in the open literature.

A Method of Spatial Processing for a Railway Crossing Control Radar System

Introduction. Railway crossing is a source of increased danger for vehicles and pedestrians. To increase the safety of traffic at railway crossings, radar systems based on antenna arrays (AA) can be used. The important requirements for radar at a railway crossing are a wide field of view (up to 90 degrees) and, at the same time, a high accuracy in determining coordinates. Therefore, an analysis of methods for constructing AAs and spatial processing for an automatic traffic control system at a railway crossing seems to be a relevant research task. Aim. Design of a method for constructing the topology of an AA and spatial processing of a radar system for monitoring traffic at a railway crossing, providing a wide field of view with a high accuracy in determining the coordinates of targets. Materials and methods. The considered method was developed based on the theory of space-time signal processing. The design of the analyzed AA topologies was carried out by the finite element method (FEM) and the finite differ-ence time domain method (FDTD) based on segments of a microstrip transmission line. Results. A method for constructing a filled transceiver antenna array and a beamforming algorithm, which provide high angular resolution and unambiguous measurement of the target's angular coordinates in a wide field of view with relatively low computational complexity, was developed. Mathematical and electrodynamic modeling of the designed AA topologies was performed. Adjusted values of the radiation patterns (RP) of the transmitting and receiving AA were obtained, which showed good agreement with the calculated values. The main design solutions regarding the construction of AA radar for a railway crossing control system are presented to provide a wide field of view when determining the coordinates of targets. Conclusion. It was shown that the width of the resulting RP can be reduced by several times compared to the width of the receiving RP when using two transmitting antennas located at the edges of the aperture. This approach is similar to that used in the MIMO technology, although requiring no coherence of transmission channels and use of a system of orthogonal signals. The findings determine the prospects of using the developed method.

Methodology for Simulation of Combined EPS and TS Wind Field and Its Influence on the Dynamic Response of a Transmission Line Segment

So far, wind loads on structures are almost exclusively evaluated by Extended Pressure Systems (EPS) cyclone models according to design codes. However, there is evidence that downburst wind fields, originating from thunderstorms (TSs) events, may have caused or contributed to the collapse of transmission line towers around the world. In this context, this work proposes a complete methodology to simulate a wind field from combined EPS (synoptic) and TS (nonsynoptic) storms. The proposed combined wind field model is applied to a real transmission line segment and the results are compared with those of the system subjected to the equivalent static loading method proposed in the IEC 60826/2003 code. The finite central differences explicit method is adopted for dynamic integration, taking into account nonlinearities. The assessment confirmed the localized and transient nature of the TS phenomenon. The results indicated that, for most of the elements analyzed, the equivalent static method for synoptic winds of IEC 60826/2003 resulted in a lower response than that obtained through the proposed combined model, which considers a TS carried by an EPS background wind. Thus, the proposed method to combine synoptic and nonsynoptic wind fields might be a useful tool to assist in the design of structures, such as transmission lines, which are susceptible to the effects of combined EPS and TS wind fields.

Expanding Functionality of Dual-Mode Resonators and Filters Using Nonuniform Transmission Line Structural Elements

The article provides an optimal synthesis of nonuniform transmission line structural elements, where resonant frequencies have a special placement. It is possible to improve the functionality of dual-mode resonators, which use these transmission segments. The optimal synthesis means that we obtain the special ratio between resonance frequencies of structural elements and have the minimum of parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m}={Z}_{\text {0max}}/{Z}_{\text {0min}}$ </tex-math></inline-formula> . We used the parametric synthesis for optimize proposed structure. It leads to stepped-impedance transmission line segments (SILS) which have the resonant frequencies with required placement and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m}= {m}_{\text {min}}$ </tex-math></inline-formula> . Two SILS pairs are synthesized. Two ends of one pair are open-circuited and the other pair is short-circuited. We added different stubs to the middle of proposed SILS. As result, four new dual-mode resonators with enhanced functions are designed. All dual-mode resonators have an extended stopband. The dual-mode resonators have reduced length relative to a half-wave resonator. The resonators allow increasing their operating frequencies. These resonators are very promising for use in dual-band BPF, so we can change the placement of one passband to another in the range <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.46 \le {f}_{2}/{f}_{1} \le 6.47$ </tex-math></inline-formula> . The measured and simulated results of two microstrip filters with new structural elements are offered.

Design Trade-Offs in the Use of Exponentially Tapered Transmission Line Segments for Impedance Transformation

A one-parameter family of designs for an exponentially tapered transmission line to match a given resistive load to a real input impedance is derived. Consideration is also given to frequency bandwidth, ripple height, and length of the matching section. Comparisons are made to the Bramham, Hamid & Chen, and Klopfenstein transmission line matching circuits. A careful examination of design trade-offs for this class of structures is made.

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&#x0D; 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. &#x0D; Method. The paper uses the method of perturbation theory of linear differential operators applied to equations describing processes in inhomogeneous long lines.&#x0D; 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. &#x0D; 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.

Wideband Unequal Power Divider With Enhanced Power Dividing Ratio, Fully Matching Bandwidth, and Filtering Performance

A new class of wideband unequal power divider with enhanced power dividing ratio, fully matching bandwidth, and filtering performance is presented. A leading triple-mode resonator is inserted in front of the power dividing junction to relax the requirement of high impedance and bring in more poles in input return loss (RL) response and isolation response. Therefore, the power dividing ratio is significantly enhanced and bandwidths of input RL and isolation are enlarged. Moreover, the cascade of the leading triple-mode resonator and the following transmission line segments corporately construct Chebyshev filtering performance. Thus, the power divider can be synthesized by the required bandwidth of RL and power dividing ratio. Examples of 4:1 and 8:1 filtering power dividers operating at 2.4 GHz are designed and fabricated. The measured power dividing ratios of two filtering power dividers are 3.8:1 and 8.1:1 with corresponding RL bandwidths of 95.8% and 97.5% (| S₁₁| < -10 dB), and the measured port-to-port isolation bandwidths are 100% (| S₃₂| < -14 dB) and 100% (| S₃₂| < -20 dB), respectively.

Analysis of Dual-mode Resonators from Transmission Line Segments

Analysis of Dual-mode Resonators from Transmission Line Segments

3D-Printed Broadband Power Divider Based on Helical-Microstrip Transmission Line Segments

3D-Printed Broadband Power Divider Based on Helical-Microstrip Transmission Line Segments

A 190.3‐dBc/Hz FoM 16‐GHz rotary travelling‐wave oscillator with reliable direction control

This letter presents a rotary travelling-wave oscillator (RTWO) with reliable direction control in a standard 130 nm complementary metal–oxide–semiconductor (CMOS) technology. To achieve low phase noise (PN), and low power consumption, 16-stages customised transmission line segments are designed and simulated on electromagnetic tools. The PN is investigated through modelling the RTWO as multiple standing-wave oscillators. The proposed oscillator achieves 11.2% tuning range, 190.3 dBc/Hz figure-of-merit (FoM) at 1 MHz offset and 192.3 dBc/Hz FoM at 10 MHz offset with 5.8-mW power consumption from 16-GHz carrier.

Improvement of External and Traction Power Supply System’s Efficiency by Normalizing the Schemes

The article deals with improvement off the efficiency of external and traction power supply systems using for example indicators of traction substations for a real electric transmission line segment of a traction network of 25 kV. The analysis of the functioning of a real section of electrified railways with traction substations, two of which are connected according to the "feeding" scheme is providing in the article. The currents in the wind-ings of traction transformers are calculate for these substations. The proportion of the currents values of the most loaded winding to the two less loaded is 2: 1. The coefficient asymmetry of currents of transformer wind-ings operating on existing traction substations is equal to 1. The results prove a significant currents asymmetry of transformers windings and phases of electric transmission lines which leads to an increasing voltage unbal-ance. New schemes for connecting traction substations for the considered section of electrified railways have been developed in order to improve the quality indicators of electrical energy. New connection schemes for three traction substations, determined according to the requirements for connecting to the external and trac-tion power supply system are presents in the article. The calculation for new schemes of connecting traction substations, similar to the previously considered option, has been performed. The values of winding currents, power transmission line phases and coefficient asymmetry were obtained for new substation connection schemes. The proposed schemes for connecting traction substations provide a decrease in the coefficient asym-metry of the winding currents from 1 to 0.5 and a decrease in the current modulus in the most loaded windings by 1.5 times. New schemes for connecting traction substations reduce the currents of the most loaded windings and phases of the power transmission line, as well as the asymmetry of currents, which ensures an improvement in the efficiency of the external and traction power supply systems of the real traction network.

A Dual-Band Rat-Race Coupler for High Band Ratio Wireless Applications

This article presents a dual-band rat-race coupler for high band ratio wireless applications. In this article, a dual-band transmission line (TL) has also been proposed to design the rat-race coupler. The proposed rat-race coupler has been developed by substituting each TL segment of a single-band rat-race coupler with the dual-band TL. To validate the design method, a rat-race coupler for 0.7- and 4.9-GHz operating frequencies has been developed. A maximum of 3.3-dB insertion loss and 20-dB return loss and isolation have been attained for both the frequency bands. Compared with the existing dual-band rat-race couplers, the proposed coupler offers dual-band operation with a high band ratio. In addition, for the first time a dual-band rat-race coupler compatible with microstrip TL and having input and output on different sides has been developed. This feature makes simpler connections when connected to other circuits.

CHARACTERISTICS OF VIBRATOR ARRAYS DIRECTIVITY ON HARMONICS OF MAIN FREQUENCY

Antenna patterns representing dependences of the directivity factor (DF) on angular coordinates for arrays formed from Yagi-Uda aerials are considered and discussed. The results of computer modelling are based on the decision of integral equations by the method of moments. Patterns that represent dependences of the coefficient of the directivity factor (DF) for an array and her elements from angular coordinates are counted on fundamental frequency and four harmonics. The data obtained confirmed the validity of the assumptions that the directivity properties of vibrator antenna arrays can significantly affect the EMC conditions for harmonics of the fundamental frequency. At these frequencies, several main maxima appear in the radiation patterns, the level of directivity in which may even exceed the maximum directivity in the main lobe at the fundamental frequency. The DF patterns shown in the article refer to the case of in-phase excitation of the active elements of the array (without supply lines). However, in the presence of such lines with sequential or mixed power supply circuits, the dependence of the directivity on the angular coordinates can change significantly. The presence of bandpass filters in the input and output stages of the radar will make it possible to largely suppress the levels of harmonic interference, however, if these filters are made on the basis of transmission line segments, their parameters at harmonic frequencies may be insufficient. Further research can be aimed at studying the spatial characteristics and directivity of vibrator antenna arrays based on wave channel antennas with an increased number of passive vibrators, as well as with various power supply and filtering schemes.

Parametric and Structural-Parametric Synthesis of Nonuniform Transmission Line Resonators

This article discusses methods of parametric and structural-parametric synthesis of resonators, which contain transmission line segments of the same length. These methods allow optimizing resonators of various configurations with different segments number $N$ and characteristic impedances $Z_{0i}$ . We will call optimal resonators if they have a minimum ratio $m = Z_{\mathrm {0max}}/Z_{\mathrm {0min}}$ at given ratio between the critical frequencies (poles and zeros of the input impedance). The input impedances of the resonators under consideration at the Richards’ frequency variable $S$ are described by the reactance functions of $N$ degree: $Z^{N}(S)$ . The parametric synthesis refers to stepped impedance resonators (SIRs). The structural-parametric synthesis refers to resonators of a more general form, which contain open- and short-circuited stubs. The methods are based on two states established in this paper: the order of the reactance function $Z^{N}(S)$ should be the minimum possible ( $N = N_{\mathrm {min}}$ ) to implement the required ratio between certain critical frequencies; the characteristic impedances of the composite sections $Z_{0i}$ take only two values $Z_{\mathrm {0min}}$ or $Z_{\mathrm {0max}}$ . These methods were used to synthesize different resonators useful for practical application. With the help of the structural-parametric synthesis, the resonators of a more complex configuration are synthesized, which significantly exceed SIRs. The results of the measurements and simulation are presented.

Corrections to “Time Domain Hybrid Method for the Coupling Analysis of Oblique Transmission Line Network Excited by Ambient Wave”

In [1], Fig. 5 is incorrect. The correct figure is provided as follows. Fig. 5. Interpolation scheme for the electric fields at the starting or ending points of each segment of oblique transmission line.

RETRACTED: Studies of the Electrodynamic Parameters of a Powdered Material Depending on the Fractional Composition in the Frequency Range of 8-12 Ghz

This article describes a method for measuring the dielectric constant and magnetic permeability of alumina powder (corundum) in the frequency range of 8-12 GHz. The results of studies of permeability and permittivity using a segment of a coaxial transmission line depending on the size of corundum particles are presented.