Transmission Line Approach Research Articles

An improved zeroth order resonator using left handed metamaterial

In this paper an improved version of zeroth order resonator (ZOR) using Left Handed Metamaterial (LHM) is reported, and its performance is compared with the earlier published ZOR. The resonator is designed based on microstrip technology using composite right left handed transmission line (CRLH TL) approach. The conventional ZOR is designed based on the CRLH TL along with two coupling slots at the input and output ports, whereas the proposed design of ZOR is based on coupling capacitors. Use of coupling capacitor in place of coupling slot improves resonance characteristic of ZOR in terms of return loss and insertion loss and also increases the operational bandwidth. The measured resonant frequency, return loss, insertion loss and fraction bandwidth of the proposed 1.5- unit cell ZOR are 1.5 GHz, -26.31 dB, -0.42 dB and 20.66% respectively, whereas for the conventional 1.5-unit cell ZOR these measured parameters are 1.8 GHz, -6.63 dB, -9.09 dB and 0.77% respectively. The frequency parameter and performance of the resonators are evaluated by full-wave electromagnetic simulator, IE3D, based on method of moments (MoM) and all these results are verified by measurements.

Experimental realization of a variable index transmission line metamaterial as an acoustic leaky-wave antenna

Development and experimental realization of an acoustic leaky wave antenna are presented. The antenna uses a one-dimensional composite right/left hand transmission line approach to tune radiation angle continually from backfire-to-endfire, including broadside, as a function of input frequency. An array of acoustically loaded membranes and open channels form a structure with negative, zero, or positive refractive index, depending on excitation frequency. The fast-wave radiation band of the antenna is determined using acoustic circuit analysis. Based on the designs specified by circuit and finite element analysis, an acoustic leaky wave antenna was fabricated, and the radiation direction measured at discrete frequencies.

Effective Surface Impedance of a Printed-Circuit Tensor Impedance Surface (PCTIS)

The surface impedance and dispersion equation of a printed-circuit tensor impedance surface (PCTIS) are derived using a modified transverse resonance technique. A PCTIS consists of a subwavelength-patterned metallic cladding over a grounded dielectric substrate. The metallic cladding is analytically modeled as a tensor impedance sheet. An explicit expression is derived for the effective surface impedance of the PCTIS using a transmission-line approach. First, the surface-impedance expression is found for a printed-circuit scalar impedance surface using the transverse resonance technique. Next, a modified transverse resonance technique is applied to an idealized tensor impedance boundary condition (TIBC) to find its dispersion equation. Finally, the analysis of the printed-circuit scalar impedance is combined with that of the idealized TIBC to find the tensor surface impedance and dispersion equation of a PCTIS. A discussion of the principal axes and the propagation of TM and TE waves is provided. The special case of electrically thin PCTISs is also analyzed and discussed.

Double-Circuit Transmission-Line Fault Location Utilizing Synchronized Current Phasors

Fault location is considered as one of the essential techniques enabling a smart grid. This paper presents a novel fault location approach for double-circuit transmission lines. Various existing algorithms usually require measurements recorded from one or two terminals of the faulted line. However, when such measurements are not available, these methods are not applicable. To fill this gap, this paper proposes a fault location method by harnessing current measurements from one or more branches, which may not be necessarily taken from the faulted section. The currents from multiple branches are synchronized and can be obtained from phasor measurement units installed in the system. The bus impedance matrix technique is exploited to develop the new method. The shunt capacitance of the line is fully considered by utilizing the distributed parameter line model. The network data are assumed to be available. When multiple synchronized current measurements are available, an optimal estimator capable of identifying possible bad measurement data and, thus, further enhancing the fault location is also proposed. Quite accurate results have been achieved based on simulation studies.

Metamaterial polarization converter analysis: limits of performance

In this paper we analyze the theoretical limits of a metamaterial converter that allows for linear-to- elliptical polarization transformation with any desired ellipticity and ellipse orientation. We employ the transmission line approach providing a needed level of the design generalization. Our analysis reveals that the maximal conversion efficiency for transmission through a single metamaterial layer is 50%, while the realistic re ection configuration can give the conversion efficiency up to 90%. We show that a double layer transmission converter and a single layer with a ground plane can have 100% polarization conversion efficiency. We tested our conclusions numerically reaching the designated limits of efficiency using a simple metamaterial design. Our general analysis provides useful guidelines for the metamaterial polarization converter design for virtually any frequency range of the electromagnetic waves.

Modeling of Crosstalk in Through Silicon Vias

This paper presents analytical formulas to extract an equivalent circuit model for coupled through silicon via (TSV) structures in a 3-D integrated circuit. We make use of a multiconductor transmission line approach to model coupled TSV structures. TSVs are embedded in a lossy silicon medium, hence they behave as metal-insulator-semiconductor (MIS) transmission lines. The models we present can accurately capture the transition between slow-wave and dielectric quasi-TEM modes, which are characteristic for MIS transmission lines, as well as the metal-oxide-semiconductor (MOS) varactor capacitance. The results agree well with 2-D quasi-static simulations and 3-D full-wave electromagnetic simulations. The derived equivalent circuit models can easily be applied in circuit simulators to analyze crosstalk behavior of TSVs in a 3-D integrated system.

Surface Impedance Measurement of Resistive Coatings at Microwave Frequencies

A simple approach to estimate the surface impedance of a thin ink deposition on dielectric substrates is described. The measured sample is transversally accommodated in a waveguide, and the scattering parameters are measured. Then, the surface impedance value is recovered by recurring to an efficient transmission-line approach. Closed-form relations are proposed, which allow removing the dispersive effect of the substrate on the estimated surface impedance. The robustness of the retrieving procedure is analyzed, showing that the one based on the transmission coefficient provides more accurate results than the reflection-based one. The positioning of the sample is also investigated, highlighting that the placement inside the waveguide leads to incorrect estimations of the surface impedance with fictitious high imaginary parts because of the presence of air gaps between the sample and the waveguide walls, which transform the uniform layer to a capacitive resistive frequency selective surface. A modified setup with a uniform resistive ink deposition pressed between the waveguide flanges is therefore adopted. Additional experimental results on the effect of the dielectric substrate and on the homogeneity of the ink deposition are reported.

Electromagnetic field coupling to arbitrary wire configurations buried in a lossy ground: a review of antenna model and transmission line approach

The paper deals with two different approaches for the analysis of electromagnetic fi coupling to arbitrary wire confi gurations buried in a lossy medium: the wire antenna theory and the transmission line method. The wire antenna formulation deals with the corresponding set of Pocklington integrodifferential equation, while the transmission line model is based on the telegrapher’s equations. The set of Pocklington equations is solved via the Galerkin‐Bubnov scheme of the indirect boundary element method, while the telegrapher’s equations are treated using the chain matrix method and fi nite difference technique, respectively. A number of illustrative computational examples pertaining to buried multiple lines and grounding systems is given in the paper.

A THREE-BAND T-JUNCTION POWER DIVIDER BASED ON ARTIFICIAL TRANSMISSION LINES

Based on the Composite Right/Left-Handed (CRLH) Transmission Line (TL) approach this paper presents a 3-band T- Junction power divider. The proposed design strategy uses a stub- loaded TL for the right-handed portion of the line; this way, with respect to a conventional CRLH line, one more degree of freedom is available. Experimental and numerical results referring to a prototype using surface-mount capacitors and inductors are reported and discussed. It is demonstrated that the artiflcial transmission line (ATL) here presented is an optimum candidate for designing high- added value microwave devices. Furthermore based on the use of metal- insulator-metal capacitors and short circuited stubs, a monolithic implementation is also proposed.

Power Cable Joint Model: Based on Lumped Components and Cascaded Transmission Line Approach

Models in high frequency range for underground power cable connections are essential for the interpretation of partial discharge (PD) signals arising e.g. diagnostic techniques. This paper focuses on modeling of power cable joints. A lumped parameter odel and a cascaded transmission line model are proposed based on scattering parameters (S -parameters) measurement on a 10 kV oil-filled PILC-PILC straight cable joint in the frequency range of 300 kHz-800 MHz. It is shown that the lumped model is suitable for up to 10 MHz while the transmission line model can cover the whole frequency range. The cascaded transmission line model is applied to simulate the reflection on a 150 kV single core XLPE straight joint. Comparison between measurement and simulation indicates that the model parameters (characteristic impedance and propagation coefficient) can be matched to predict the joint's propagation characteristics.

An improved full scanning antenna using left-handed materials

An improved version of full scanning antenna using left-handed metamaterial is reported in this article. The antenna profile is designed based on microstrip technology using balanced composite right left handed transmission lines (CRLH TL) approach. Conventional LC network representation of the CRLH TL uses cascaded combination of interdigital capacitor (IDC) in series and vias to the ground plane at the stub ends in shunt, whereas in this article, the design of full scanning antenna using wire-bonded IDC is reported and its performance is compared with conventional IDC based full scanning antenna. Dispersion diagram of the balanced CRLH TL based dominant mode leaky wave antenna shows the capability of backfire (−90° < θ < 0°) to broadside (θ = 0°) and to endfire (0° < θ < 90°) scanning. Radiation patterns confirm the full scanability of the antenna and it also shows the designed structure has reduced sidelobes in the endfire radiations. Simulated and measured return loss characteristics of the reported antenna structure show an increase in the antenna's operational bandwidth. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:261–265, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27333

Vortexlike Power Flow at the Interfaces of Metamaterial Lens

The metamaterial lens with DPS/DNS/DPS structure has been realized by using the two-dimensional (2D) isotropic transmission line approach. We studied the vortexlike power flow at the interfaces of metamaterial lens and validated by the finite-difference time-domain (FDTD) simulator. The computational results showing its different conditions near DPS/DNS and other kinds of interfaces are obtained by CST STUDIO SUITE at different frequencies, and demonstrate the intuitionistic power location at the metamaterial lens interfaces.

Bi-Band Bow-Tie Antennas Array Design Using a Simple Equivalent Transmission Line Model

In this paper we propose a simple equivalent and accurate transmission line model for bi-band bow-tie antennas array design over a band of frequencies for satellite communications. This model uses the resistance of a square element that appears at the edges of the antenna (radiating slots). To test this model, two antennas array were simulated and results were compared with those obtained by a rigorous method (moment’s method) of the simulator ADS/Momentum. Using this transmission line approach the resonant frequency, return loss, VSWR, reflected phase, input impedance can be determined simultaneously. The results confirm the validity of the proposed model.

Experimental Study of Tunneling modes in Photonic Crystal Heterostructure Consisting of Single-Negative Materials

The pair structure and the photonic crystal heterostructure consisting of ∊-negative and μ-negative materials are successfully fabricated by using the transmission line approach. We experimentally investigate the tunneling mode properties by simulating and measuring the scattering parameters and phase shifts. It is shown that the pair structure and the photonic crystal heterostructures possess tunneling modes when the general zero average permittivity and zero average permeability condition are satisfied. At the tunneling frequency, the field (voltage) mainly concentrates in the center of the constructed structures based on the amplification of the evanescent wave. Moreover, the tunneling mode of the photonic crystal heterostructure has zero phase delay. The characteristics have potential applications in design of zero phase delay filters.

Proposed model for quantification of dissolution—and evolution of a steel-CO2 solution interface by the transmission line approach

The corrosion mechanisms occurring at the homogeneous porous layer was determined assuming that the pores had a cylindrical geometry, and that the initial interface of a carbon steel-CO2 solution behaved as a transmission line (TL). TL modeling quantitatively assessed the impedance distribution and the mesoporous layer formation and evolution at the interface, while describing the physical characteristics of the mesoporous FeCO3 layer at the base and wall within the initial pore. The TL helped to characterize four stages during the interfacial evolution: active, active-porous layer, mixed layer, and the reactive stages. Using TLs helped to quantify the dissolution process and distinguish the mechanisms with good agreement between calculated magnitudes and experimental data.

Spectral Models of Lossy Nonuniform Multiconductor Transmission Lines

This paper presents a new approach for modeling nonuniform lossy transmission lines. The proposed technique is based on the concept of Green's function of the differential problem represented by the Telegrapher's equations. The Green's function of nonuniform one-dimensional problems is expanded in terms of the eigenfunctions of the uniform problem, yielding a rational macromodel that has a simple representation in the time-domain. The use of global basis functions also addresses the problem of space dependence of the per-unit-length parameters, completely avoiding to resort to any discretization technique. Several examples of single and coupled nonuniform lines are presented and the accuracy of the method is verified by comparison with reference results.

Corporate-Feed Multilayer Bow-Tie Antenna Array Design Using a Simple Transmission Line Model

A transmission line model is used to design corporate-fed multilayered bow-tie antennas arrays; the simulated antennas arrays are designed to resonate at the frequencies 2.4 GHz, 5 GHz, and 8 GHz corresponding to RFID, WIFI, and radars applications. The contribution of this paper consists of modeling multilayer bow-tie antenna array fed through an aperture using transmission line model. The transmission line model is simple and precise and allows taking into account the whole geometrical, electrical, and technological characteristics of the antennas arrays. The proposed transmission line model showed its interest in the design of different multilayered bow-tie antennas and predicted the correct resonance frequency for different applications in telecommunications. To validate the proposed transmission line model, the simulation results obtained are compared with those obtained by the method of moments. The results of simulations are presented and discussed. Using this transmission line approach, the resonant frequency, input impedance, and return loss can be determined simultaneously. The paper reports several simulation results that confirm the validity of the developed model. The obtained results are then presented and discussed.

Electromagnetic Field Coupling to Overhead Wire Configurations: Antenna Model versus Transmission Line Approach

The paper deals with two different approaches for the analysis of electromagnetic field coupling to finite length overhead wire: the wire antenna theory (AT) and the transmission line (TL) method. The analysis is carried out in the frequency and time domain, respectively. Within the frequency domain analysis the wire antenna formulation deals with the corresponding set of Pocklington integrodifferential equation, while the transmission line model uses the telegrapher's equations. The set of Pocklington equations is solved via the Galerkin-Bubnov scheme of the Indirect Boundary Element Method (GB-IBEM), while the telegrapher’s equations are treated using the chain matrix method and the modal equation to derive per-unit-length parameters. For the case of the time domain analysis AT model uses the space-time Hallen integral equation set, while TL approach deals with the time domain version of the telegrapher’s equations. Hallen equations are handled via time domain version of GB-IBEM, while time domain telegrapher’s equations are solved by using Finite Difference Time Domain (FDTD) method. Many illustrative computational examples for the frequency and time domain response, respectively, for several configurations of overhead wires, obtained via different approaches, are given in this paper.

Three-dimensional simulations of an induction motor including eddy current effects in core laminations

This work is motivated by the investigation of the common mode ground current which occurs in induction machines controlled by pulse-width modulation (PWM) at higher frequencies. In order to quantify this current, the common mode impedance of the motor has to be determined. Using the transmission line approach the model parameters are extracted from both two-dimensional (2D) and three-dimensional (3D) field simulations. 2D finite-element (FE) analysis is an efficient tool for simulating the entire motor cross-section. However, eddy currents in the laminations cannot be modelled explicitly and have to be approximated by a semi-analytical formulation. The study investigates the accuracy of this model for a wide frequency range (10 Hz, , 1 MHz). For this purpose, a specialised 3D simulation tool for induction motors was developed, taking into account the actual distribution of eddy currents in the laminations. Simulation results are presented for a simple one conductor test case as well as for an entire motor cross-section of an existing 240 kW motor.

A FREQUENCY SELECTIVE ABSORBING GROUND PLANE FOR LOW-RCS MICROSTRIP ANTENNA ARRAYS

An e-cient strategy for reducing the signature of an antenna is to substitute the conventional solid ground plane with a patterned ground plane thus letting the incoming energy to pass through the structure except over the operating band of the antenna. However, in a real environment, the energy ∞owing through the FSS (Frequency Selective Surface) can be intercepted by eventual scatterers located behind the antenna, so to nullify the RCS (Radar Cross Section) reduction. To overcome this drawback, a novel composite structure is proposed which is able to dissipate such energy by placing a thin absorbing layer below the FSS ground. It is shown that a careful analysis has to be performed to accomplish this goal since the transparent antenna array and the backing absorber strongly interact and thus they cannot be separately designed. The optimal value of the foam spacer thickness between the FSS ground and the absorbing layer is investigated by an e-cient equivalent transmission line approach. Criteria for enlarging the low-RCS band with respect to the free space design are also provided. An antenna array prototype backed by the thin multilayer structure is flnally manufactured and tested.