Transmission Line Technique Research Articles

Dielectric and Tunability Properties of Nanostructured Nd-modified Pb(ZrxTi1-x)O3 Thin Films up to Microwave Frequencies

Dielectric properties of nanocrystalline Nd-modified Pb(ZrxTi1-x)O3 thin films were studied in frequency range f = 100 Hz –20 GHz. Thin films were prepared by pulsed laser deposition on MgO(100) substrates. Inter-digital electrodes and coplanar waveguide transmission line technique were used for dielectric characterization. In the dielectric function ɛr(f, T), two interesting anomalies were found at low frequencies. Diffusive phase transition had relaxor-type behaviour, and an extra dielectric relaxation maxima were found below Curie temperature TC. At higher frequencies above 5 GHz, relative permittivity ɛr(f) response was flat up to 20 GHz, and high maximum tunability nr,max = 19% was achieved.

Heterogeneous trench-assisted few-mode multi-core fiber with low differential mode delay.

We propose a kind of heterogeneous multi-core fiber (Hetero-MCF) with trench-assisted multi-step index few-mode core (TA-MSI-FMC) deployed inside. After analyzing the impact of each parameter on differential mode delay (DMD), we design a couple of TA-MSI-FMCs with A(eff) of 110 μm2 for LP01 mode. DMD of each TA-MSI-FMC is smaller than |170| ps/km over C + L band and the total DMD can approach almost 0 ps/km over C + L band if we adopt DMD managed transmission line technique by using only one kind of Hetero-TA-FM-MCF. For such Hetero-TA-FM-MCF, crosstalk is about -30 dB/100km at wavelength of 1550 nm as bending radius becomes larger than 15 cm, core number can reach 12, a relative core multiplicity factor (RCMF) is 15.7, and the RCMF can even reach 26.1 if we treat LP11 mode as two special modes thanks to the multiple-input-multiple-output technology.

Note: Electrical detection and quantification of spin rectification effect enabled by shorted microstrip transmission line technique

We describe a shorted microstrip method for the sensitive quantification of Spin Rectification Effect (SRE). SRE for a Permalloy (Ni80Fe20) thin film strip sputtered onto SiO2 substrate is demonstrated. Our method obviates the need for simultaneous lithographic patterning of the sample and transmission line, therefore greatly simplifying the SRE measurement process. Such a shorted microstrip method can allow different contributions to SRE (anisotropic magnetoresistance, Hall effect, and anomalous Hall effect) to be simultaneously determined. Furthermore, SRE signals from unpatterned 50 nm thick Permalloy films of area dimensions 5 mm × 10 mm can even be detected.

A novel redundant haar lifting wavelet analysis based fault detection and location technique for telephone transmission lines

The redundant lifting scheme is a perfect tool for wavelet decomposition and reconstruction conducted in the time domain without decimation procedure. In this paper based on the redundant haar lifting wavelet analysis and time domain reflectometry (RHLW-TDR) a novel fault detection scheme is introduced to detect the fault of the telephone transmission lines. The fault time tags are extracted directly from the wavelet detail coefficients. Furthermore, the proposed algorithm is improved to adaptive morphological redundant haar lifting wavelet analysis based time domain reflectometry (AMRHLW-TDR). Comparing to the conventional wavelet based TDR technique, the simulation test and practical experiment results verified the accuracy and convenience enhancement of the proposed methodology and its improved version.

Comparison of electromagnetic shielding effectiveness of conductive single jersey fabrics with coaxial transmission line and free space measurement techniques

The aim of this study is to investigate the electromagnetic shielding effectiveness (EMSE) of thin and lightweight knitted fabrics that are suitable for casual wear like t-shirts. For the purpose of having a low production cost, metal/cotton conductive composite yarns are produced by a yarn doubling technique, involving stainless steel wires (35 μm, 50 μm) or copper wires (50 μm, 70 μm) and Ne30/1, Ne40/1, Ne60/2, Ne80/2 count cotton yarns. Single jersey fabrics are knitted on an E20 circular knitting machine with the same machine settings. Coaxial transmission line and free space measurement (by using an anechoic chamber) techniques are used for the EMSE measurements in the frequency range of 100 MHz–1.5 GHz and 1 GHz–18 GHz respectively. The free space measurement technique test results reveal that single jersey knitted fabrics have EMSE ability for the electric field polarization in the same direction as the main direction of the conductive metal wires in the fabric. It is observed that all single jersey fabric structures have more than 7 dB (80% or better) EMSE for GSM-850 and GSM-900 cellular phone communication bands according to coaxial transmission line equipment test results. SNK test results of both test methods reveal that, while 100% cotton fabrics do not have EMSE ability, cotton yarn count is highly significant on the EMSE of single jersey fabrics with conductive composite yarns. Fabrics with two-ply fine cotton yarns (Ne60/2 and Ne80/2) have higher EMSE values than the fabrics with one-ply cotton yarn of the same yarn count (Ne30/1 and Ne40/1).

Planar quadrature RF transceiver design using common-mode differential-mode (CMDM) transmission line method for 7T MR imaging.

The use of quadrature RF magnetic fields has been demonstrated to be an efficient method to reduce transmit power and to increase the signal-to-noise (SNR) in magnetic resonance (MR) imaging. The goal of this project was to develop a new method using the common-mode and differential-mode (CMDM) technique for compact, planar, distributed-element quadrature transmit/receive resonators for MR signal excitation and detection and to investigate its performance for MR imaging, particularly, at ultrahigh magnetic fields. A prototype resonator based on CMDM method implemented by using microstrip transmission line was designed and fabricated for 7T imaging. Both the common mode (CM) and the differential mode (DM) of the resonator were tuned and matched at 298MHz independently. Numerical electromagnetic simulation was performed to verify the orthogonal B1 field direction of the two modes of the CMDM resonator. Both workbench tests and MR imaging experiments were carried out to evaluate the performance. The intrinsic decoupling between the two modes of the CMDM resonator was demonstrated by the bench test, showing a better than -36 dB transmission coefficient between the two modes at resonance frequency. The MR images acquired by using each mode and the images combined in quadrature showed that the CM and DM of the proposed resonator provided similar B1 coverage and achieved SNR improvement in the entire region of interest. The simulation and experimental results demonstrate that the proposed CMDM method with distributed-element transmission line technique is a feasible and efficient technique for planar quadrature RF coil design at ultrahigh fields, providing intrinsic decoupling between two quadrature channels and high frequency capability. Due to its simple and compact geometry and easy implementation of decoupling methods, the CMDM quadrature resonator can possibly be a good candidate for design blocks in multichannel RF coil arrays.

Loss Computation of Multilayer Coplanar Waveguide using Single Layer Reduction Method

In this paper, the quasi-static spectral domain approach (SDA) and single layer reduction (SLR) method applicable for multilayer coplanar waveguide (CPW) on isotropic dielectric substrate that incorporates two layer model of conductor thickness is used to compute the impedance, effective dielectric constant, dielectric loss and conductor loss. The transverse transmission line (TTL) technique is used to find the Green’s function for the multilayer CPW in Fourier domain. Dielectric loss of multilayer coplanar waveguide is computed by converting multilayer CPW structure into equivalent single layer CPW using SLR method. Perturbation method is used to compute the conductor loss. The effect of finite conductor thickness is analysed on the impedance, effective dielectric constant, dielectric loss and conductor loss. The present formulation also accounts for low frequency dispersion in computation of quasi-static effective dielectric constant and characteristic impedance.

A Time-Domain Adjoint Variable Method for Materials With Dispersive Constitutive Parameters

We present the first time-domain adjoint variable method (AVM) algorithm for materials with dispersive constitutive parameters. We develop our algorithm based on transmission-line modeling techniques for electromagnetic problems. The developed theory is based on utilizing the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> -domain representation of the dispersive materials, which can model arbitrary dispersive behavior. We develop a formulation similar to the original AVM theory for nondispersive materials. The theory has been successfully applied to problems with dispersive materials modeled by the Drude, Debye, and Lorentz models.

Time-Domain Green's Function-Based Parametric Sensitivity Analysis of Multiconductor Transmission Lines

We present a new parametric macromodeling technique for lossy and dispersive multiconductor transmission lines. This technique can handle multiple design parameters, such as substrate or geometrical layout features, and provide time-domain sensitivity information for voltages and currents at the ports of the lines. It is derived from the dyadic Green's function of the 1-D wave propagation problem. The rational nature of the Green's function permits the generation of a time-domain macromodel for the computation of transient voltage and current sensitivities with respect to both electrical and physical parameters, completely avoiding similarity transformation, and it is suited to generate state-space models and synthesize equivalent circuits, which can be easily embedded into conventional SPICE-like solvers. Parametric macromodels that provide sensitivity information are well suited for design space exploration, design optimization, and crosstalk analysis. Two numerical examples validate the proposed approach in both frequency and time-domain.

Varying Slot Lengths Strip Loading Squared Dielectric Resonator Reflectarray

a new type of dielectric resonator reflectarray composed of 529 elements covering an area of 276 x 276 cm<SUP>2</SUP> is constructed. The unit cell consists of squared DRA supported on a strip with variable slot length, a dielectric layer and a conducting ground plane. The full phase of 360 degree of the array elements can be obtained by superposition two slot-strip sizes. Two types of feeding were analyzed, the first is center fed reflectarray while the second is offset feed to reduce the feeder blockage and as a result the antenna efficiency is improved. The antenna has 10% bandwidth for 1 dB gain variation is obviously wider than that of conventional reflectarray antenna while the offset fed reflectarray provide better far field pattern with back lobes reduction by -5 dB and side lobe by -2 dB. A rectangular X- band pyramidal horn was used in both reflectarrays which have 23 x 23 elements of with cells separation of 12 mm that less than 15 mm (lambda/2) for avoiding grating lobes. CST microwave studio<SUP>©</SUP>(finite integral technique) package is applied and compared with microstripes<SUP>©</SUP> package (transmission line technique) with good agreements between them. The mutual coupling between the feeding horn and the elements of the reflectarray are considered. At 10 GHz, the antenna provides a 3-dB beamwidth of 6 degree with a gain of 28 dB. The antenna bandwidth within 1dB gain variation is found to be 13% and aperture efficiency of 59%.

In Situ Moisture Content Monitoring Sensor Detecting Mutual Coupling Magnitude Between Parallel and Perpendicular Dipole Antennas

This paper presents an in situ moisture content sensor based on a switched-polarization dipole antenna that detects the magnitude of mutual coupling between perpendicular and parallel polarizations. Three aspects of the sensor development are presented: a new closed-form calculation of mutual impedance of perpendicular polarization dipole antenna, an antenna design, and an investigation of performance enhancement. As the sensor detects only the magnitude of mutual coupling, it is low cost and low profile and needs less processing time. Thus, it is suitable for a closed-loop drying system. Our study has shown that the values of the dielectric constants measured by this sensor are comparable to the reference values from the transmission line technique in the previous work. However, there are significant differences in the values of the dielectric loss factors because the structure of the presented sensor is not a closed boundary like the transmission line sensor. Therefore, error compensation has been developed to correct the results. This sensor, in a closed-loop drying system, has shown good performance for in situ monitoring and real-time monitoring. Consequently, it is very suitable for monitoring the moisture content of paddy (rough rice).

Magnetization Process in Thin Laminations up to 1 GHz

Amorphous and nanocrystalline ribbons with transverse anisotropy have been characterized by magneto-optical, fluxmetric, and transmission line techniques from DC to 1 GHz. The contributions of domain wall displacements and magnetization rotations to the magnetization process, singled out by direct domain observations, consistently fit with the observed dependence of complex permeability and energy losses on frequency. With the domain wall motion suffering progressive hindering with increasing frequency and falling into full relaxation on reaching the MHz range, the magnetization process becomes amenable to a classical description, the concept of loss decomposition being secured. For this description, the conventional rate-independent constitutive relation for the magnetic material proves, however, inadequate. The diffusion equation for the electromagnetic field is therefore coupled with the Landau-Lifshitz-Gilbert equation, taken as a dynamic constitutive magnetic equation, and a solution is worked out by a numerical procedure. Magnetization and eddy-current field are thus obtained versus time at any point of the lamination, account being taken of the exchange field and its restraining action on the skin effect. The so calculated magnetic loss behavior turns out to correctly describe the high-frequency results, while coalescing with the classical eddy-current loss prediction at low frequencies.

A Fault Location Technique for Two-Terminal Multisection Compound Transmission Lines Using Synchronized Phasor Measurements

This paper presents a fault location technique for two-terminal multisection compound transmission lines, which combine overhead lines with underground power cables, using synchronized phasor measurements acquired by global positioning system (GPS) based phasor measurement units (PMUs) or digital relays with embedded PMU or by fault-on relay data synchronization algorithms. The technique is extended from a two-terminal fault location method with synchronized phasor measurements as inputs. A novel fault section selector is proposed to select the fault line section in advance. The proposed technique has the ability to locate a fault no matter where the fault is on overhead line or underground power cable. The adopted technique has a solid theoretical foundation and is direct and simple in terms of computational complexity. Both extensive simulation results and field test results are presented to demonstrate the effectiveness of the proposed scheme. The proposed technique has already been implemented in the Taiwan power system since the year 2008. Up to the present, the proposed technique yields excellent performance in practice.

Reduced Contact Resistance in Inkjet Printed High-Performance Amorphous Indium Gallium Zinc Oxide Transistors

Solution processing of amorphous metal oxide materials to fabricate thin-film transistors (TFTs) has received great recent interest. We demonstrate here an optimized "ink" and printing process for inkjet patterning of amorphous indium gallium zinc oxide (a-IGZO) TFTs and investigate the effects of device structure on derived electron mobility. Bottom-gate top-contact (BGTC) TFTs are fabricated and shown to exhibit electron mobilities comparable to a-Si:H. Furthermore, a record electron mobility of 2.5 cm(2) V(-1) s(-1) is demonstrated for bottom-gate bottom-contact (BGBC) TFTs. The mechanism underlying such impressive performance is investigated using transmission line techniques, and it is shown that the semiconductor-source/drain electrode interface contact resistance is nearly an order of magnitude lower for BGBC transistors versus BGTC devices.

High-speed superimposed-based protection of series-compensated transmission lines

This study presents a sub-cycle power frequency-based fault direction discrimination and fault classification algorithm for the series-compensated transmission lines. Also, it provides an accurate estimation for the fault occurrence instant which is helpful in synchronised waveforms-based pilot protective schemes. The proposed algorithm is based on capturing the initial change in the voltage and current waveforms caused by occurrence of a fault. The high-frequency components of the fault signals are first filtered out, and then the signals are sampled at a relatively low sampling rate. Unlike the conventional relative-phase-angle-based directional relays, the proposed algorithm is not affected by the current and voltage inversion phenomena due to the presence of series capacitor in the fault loop. Extensive simulation studies are performed to evaluate the proposed algorithm performance. The obtained results show that the proposed algorithm provides a simple and a very fast and reliable protection technique for power transmission lines. This algorithm also covers non-compensated transmission lines and is able to well discriminate the fault direction even if the post-fault voltage amplitude becomes too small. It is also tested using some real data recorded from a high-voltage transmission system.

Theory and Experiment of the Hollow Rectangular Dielectric Resonator Antenna

For the first time, the dielectric waveguide model (DWM) is used to calculate the resonance frequency of the hollow rectangular dielectric resonator antenna (DRA). In the analysis, the transverse transmission line technique is used along with the effective dielectric constant method to obtain characteristic equations of the hollow DRA. Good agreement between the calculation, measurement, and HFSS simulation is observed. The theory was used to facilitate the design of a strip-fed circularly polarized (CP) hollow DRA. It provides a wide 3-dB axial-ratio bandwidth of 12.4%, which is ~ 3 times of that of the solid CP DRA.

Measurement of Special Shielding Materials at S and C Band Using Improved Free-Space Transmission Technique

In this paper we discuss state of the art in the field of shielding materials investigation. Two types of newly manufactured shielding materials (nonwoven and fabric) were measured using improved free-space transmission technique at 25 GHz depending on electromagnetic wave (EM) polarization and antenna to specimen distance. Results of shielding effectiveness (SE) evaluation based on measured complex transmission coefficients (S21) were presented and compared with SE measured using coaxial transmission line technique. Also results of surface resistance measurements with the four-probe technique for the test materials are shown. Keywords—Nonwoven, fabric, shielding effectiveness, freespace measurements, surface resistivity.

Dielectric Properties of Polymer Electrolyte Membranes Measured by Two-Port Transmission Line Technique

The microwave dielectric properties of perfluorosulfonic acid membranes are characterized by a two-port transmission line technique. Two dielectric relaxation modes are observed in the microwave region (0.045-26 GHz) at 25{degree sign}C. The higher frequency process observed is identified as the cooperative relaxation of bulk-like water, whose amount was found to increase linearly with water content in the polymer. The lower-frequency process, characterized by longer relaxation times (20-70 picoseconds), is attributed to water molecules that are loosely bound to sulfonate groups. The loosely bound water amount was found to increase with hydration level at low water content, and levels-off at higher water contents. Flemion SH150, which has an equivalent weight of 909 g/equiv, displays higher dielectric strengths for both of these water modes compared to Nafion 117 (equivalent weight of 1100 g/equiv).

Parametric Macromodeling of Lossy and Dispersive Multiconductor Transmission Lines

We propose an innovative parametric macromodeling technique for lossy and dispersive multiconductor transmission lines (MTLs) that can be used for interconnect modeling. It is based on a recently developed method for the analysis of lossy and dispersive MTLs extended by using the multivariate orthonormal vector fitting (MOVF) technique to build parametric macromodels in a rational form. They take into account design parameters, such as geometrical layout or substrate features, in addition to frequency. The presented technique is suited to generate state-space models and synthesize equivalent circuits, which can be easily embedded into conventional SPICE-like solvers. Parametric macromodels allow to perform design space exploration, design optimization, and sensitivity analysis efficiently. Numerical examples validate the proposed approach in both frequency and time domain.

Investigation of Sub-10-nm Diameter, Gate-All-Around Nanowire Field-Effect Transistors for Electrostatic Discharge Applications

Electrostatic discharge (ESD) robustness of a promising nanoscaled device, the gate-all-around nanowire field-effect transistor (NW FET), was characterized for the first time using the transmission-line pulsing technique. The effects of gate length, nanowire dimension, and nanowire count on the failure current, leakage current, trigger voltage, and on-resistance were investigated. ESD performances of the gate-all-around NW FET and other nanostructure devices, such as the poly-Si nanowire thin-film transistor and FinFET were also compared and discussed.