Two-wire Transmission Line Research Articles

Ultra-broadband direct dielectric spectroscopy of liquids using a calibrated Microwave-Fluidic vertical Two-Wire sensor with Bi-Material 3D printed chamber

A novel ultra-broadband dielectric spectroscopy technique for liquids is introduced. A two-wire transmission line sensor is employed in which the liquid-under-test comprises fully the propagation medium ensuring high sensitivity and direct permittivity measurement. A vertical wire arrangement is exploited fed by a double-sided parallel stripline with a microstrip interface and no bandwidth-limiting impedance transformation. A seal-integrated flex-rigid 3D-printed liquid container is developed for robust assembly. A raw measured propagation constant correction is proposed through setup calibration using only one reference liquid, which can be air. Sensor operation and design aspects are discussed in detail and an exemplary sensing setup is developed for experimental validation. A set of liquids is characterized within a three-decade bandwidth up to 42 GHz and fitted into a relaxation model along with a comparison against industry-standard broadband open-coax sensor captured data. The conducted study and error analysis certified the performance of the proposed setup.

Efficiency Analysis for Inductive Power Transfer Using Segmented Parallel Line Feeder

Parallel line feeder (PLF) consisting of a two-wire transmission line operating in the MHz band has been proposed as a wide-coverage short-distance wireless charging. In the MHz band, a PLF of several meters suffers from standing wave effect, resulting in fluctuation in power transfer efficiency accordingly to the receiver's position. This paper studies a modified version of the system, where the PLF is divided into individually compensated segments to mitigate the standing wave effect. Modelling the PLF as a lossy transmission line, this paper theoretically shows that if the segments' lengths are properly determined, it is able to improve and stabilize the efficiency for all positions. Experimental results at 27.12 MHz confirm the theoretical analysis and show that a fairly high efficiency of 70% can be achieved.

Antenna Current Calculation Based on Equivalent Transmission Line Model.

This paper provides a new way for spatial current/field profiles for frequency-selective surface analytical approximation. It confirms that the per unit length radiation resistance of an equivalent transmission line model for line antenna has little influence on the normalized current distribution. The two-wire equivalent transmission line model (typically used for transmitting line antenna) is applied to the receiving line antenna. In this case, the corresponding incident field is decomposed into odd and even mode for asymmetric distribution. A one-wire equivalent transmission line model is then introduced for any antenna composed of relative narrow strips. The incident field does not need to be decomposed. According to the simulation, the transmission line loss has little influence on the current distribution.

Nanoscale Electrical Excitation of Distinct Modes in Plasmonic Waveguides.

The electrical excitation of guided plasmonic modes at the nanoscale enables integration of optical nanocircuitry into nanoelectronics. In this context, exciting plasmons with a distinct modal field profile constitutes a key advantage over conventional single-mode integrated photonics. Here, we demonstrate the selective electrical excitation of the lowest-order symmetric and antisymmetric plasmonic modes in a two-wire transmission line. We achieve mode selectivity by precisely positioning nanoscale excitation sources, i.e., junctions for inelastic electron tunneling, within the respective modal field distribution. By using advanced fabrication that combines focused He-ion beam milling and dielectrophoresis, we control the location of tunnel junctions with sub-10 nm accuracy. At the far end of the two-wire transmission line, the guided plasmonic modes are converted into far-field radiation at separate spatial positions showing two distinct orthogonal polarizations. Hence, the resulting device represents the smallest electrically driven light source with directly switchable polarization states with possible applications in display technology.

Antenna Array with TEM-Horn for Radiation of High-Power Ultra Short Electromagnetic Pulses

An antenna array with short shielded transverse electromagnetic horns (S-TEM-horns) for emitting high-power radiation of ultra-short electromagnetic pulses (USEMP) has been created and researched. The antenna unit consists of an ultra-wideband antenna array with four S-TEM horns, with each connected to a two-wire HF transmission line, and these four lines are connected to an antenna feeder. This feeder is connected to a semiconductor generator with the following parameters: a 50 Ohm connector, 10–100 kV high-voltage monopolar pulses, a rise time of about 0.1 ns, FWHM = 0.2–1 ns, and pulse repetition rates of 1–100 kHz. The antenna array was designed and optimized to achieve a high efficiency of about 100% for the antenna aperture by using a 2 × 2 array with S-TEM-horns, with shielding rectangular plates for the return current. The transient responses were studied by simulation using the electromagnetic 3D code “KARAT” at the time domain and experimentally with the use of our stripline sensor for measurement of the impulse electrical field with a 0.03 ns rise time and a 7 ns duration at the traveling wave. The radiators were emitting USEMP waves with a hyperband frequency spectrum of 0.1–6 GHz. The radiation with an amplitude of 5–30 kV/m of the E-field strength at a distance of up to 20 m was successfully applied to test the electronics for immunity to electromagnetic interference.

Efficient conversion from spoof surface plasmon polaritons to radiation mode.

A direct conversion from spoof surface plasmon polaritons (SSPPs) to radiation mode is proposed. A modified parallel two-wire SSPP transmission line is the key to the conversion, which is composed of traditional unit cells with slots among them. Taking advantages of the slots, the phase velocity of electromagnetic waves is larger than that of light, leading to the radiation. Both simulated and measured results show that the radiation occurs from 7.6 to 11 GHz, and the radiation angle keeps nearly stable in the whole operating frequency band, which can be predicted by theoretical calculation. The average gain and efficiency is 6.41 dBi and around 90%, respectively. The simple structure with flexibly tunable operating frequency makes the proposed design promising in planar integrated communication systems.

Direct Broadband Dielectric Spectroscopy of Liquid Chemicals Using Microwave-Fluidic Two-Wire Transmission Line Sensor

A novel robust approach for permittivity measurements of liquid materials in a wide frequency range is proposed. A high-sensitivity microwave-fluidic sensor is developed enabling direct determination of liquid samples' permittivity from the measured sensor's propagation constant. Importantly, neither sensor calibration using liquid standards nor sensor's geometry (except length) information is required, which is very advantageous for industrial applications. This is achieved through the sensor's geometry, which is a two-wire transmission line (TWL) encapsulated in a 3-D printed container, and thus, the liquid-under-test fully encloses the propagating electromagnetic waves. The measurement setup comprises the sensor cascaded between two microstrip-to-TWL transitions for which a simplified de-embedding procedure is proposed using only a THRU standard. For demonstration, a setup was developed with transitions operating within 1-10 GHz and tested up to 18 GHz by measurement of a set of alcohols to produce useful data within the transition bandwidth, which can be extended at the cost of increased uncertainty by postprocessing. Finally, the measurement error study has shown that a relatively low uncertainty and error with respect to the reference is obtained, verifying the usability of the developed measurement technique.

Electronic-components less fully textile multiple resonant combiners for body-centric near field communication

Smart and e-textiles have nowadays an important increasing place in the garment industry. The rise of embedded telecommunications, especially smartphones in our pocket, enables us to provide a power source and a wireless link for smart textiles. The main issue is to develop garments able to receive power from smartphones and communicate with them without flexibility and comfort constraints bound to embedded solid-state electronic components. Consequently, this article aims to develop a fully textile NFC combiner to transfer data and power between a smartphone and sensors without any electronic components. It precisely describes textile NFC multiple combiners composed of textile NFC antennas linked by two-wire transmission lines. Also, theoretical analysis, simulations, and experiments have been conducted to adapt the resonant frequency of such structures to the NFC technology (13.56 MHz). Finally, our article generalizes textile NFC combiner resonant frequency equations for multiple combiners with any number of antennas.

Modelling EM-Coupling on Electrical Cable-Bundles with a Frequency-Domain Field-to-Transmission Line Model Based on Total Electric Fields

This article deals with modelling of EM-coupling on cable-bundles installed in 3D structures. It introduces a modified-Field-to-Transmission-Line model for which the specificity is to account for the reciprocal interaction between EM-fields and induced currents by considering equivalent total field sources. The first part of the paper is devoted to the derivation of this model starting from Agrawal’s classical Field-to-Transmission-Line applied on a two-wire Transmission-Line and leads to a Transmission-Line model in which the signal-wire is now referenced to a fictitious surrounding cylinder acting as a return conductor. The modified-Field-to-Transmission-Line model is then obtained by modifying this derived-model in such a way that is made compatible with numerical approaches and tools based on Agrawal’s Field-to-Transmission-Line model. This modification involves a kL coefficient equal to the ratio of the two per-unit-length inductances of the classical and derived Field-to-Transmission-Line models. Validations of this modified formulation clearly show the capability of this model to predict precise wire responses including EM-radiation losses. The second part of the paper is devoted to its extension to Multiconductor-Transmission-Line-Networks. The process relies on the capability to define an equivalent wire model of the cable-bundle in order to derive the kL coefficient and to numerically evaluate equivalent total field sources. Validation of this extrapolation is presented on a real aircraft test-case involving realistic cable-bundles in order to assess the potentiality of the method for future problems of industrial complexity.

Method for designing drop-of-wire recognition systems on sections of undistorted two-wire power transmission lines

In this work a general statement of the problem of designing distributive electrical systems that recognize breakage of wires on sections of power lines using a multifunctional wire with an isolated residential wire is formulated. The use of overhead wires with the proposed construction of the housing will make it possible to solve many electrical problems very easily and cheaply without the use of expensive equipment. The correspondence table of the information current values of the power supply unit I 0 and of the wire breakdowns on the sections in the two-wire transmission line is obtained by simulation. The proposed method of diagnostics and monitoring of the state of power lines is not expensive and allows the maintenance staff, being at the substation, to detect rapidly and remotely the breakage of wires on the parts of the network and the distance to it, In order to ensure that the repair crew is sent to the exact location of the damage, this will improve the reliability of the electrical supply to consumers. This is achieved by the fact that the information wire has an independent power supply and thus allows for control of the network at any time.

A Polarization-Actuated Plasmonic Circulator.

A circulator for surface plasmon polaritons (SPPs) based on a plasmonic two-wire transmission-line (TWTL) structure is experimentally realized. A TWTL offers two distinct plasmon modes that can be independently excited, solely determined by the polarization of the laser field. Through controlled superposition of the two modes, TWTLs are exploited to enable polarization-actuated plasmonic circulators. In the first demonstration, the coupling antennas to the plasmonic circulator are designed to circulate SPPs sensitive to linearly polarized excitation. In the second design, the circulator reacts to the spin angular momenta carried by circularly polarized laser excitations. In both cases, the SPP circulation directions are directly controlled by the laser polarization, and the number of ports is easily expandable. Experimentally, a wide optical operational bandwidth of ∼100 nm is achieved. The results show a major step toward the realization of multifunctioning photonic nanocircuitry.

Modal Symmetry Controlled Second-Harmonic Generation by Propagating Plasmons.

A new concept for second-harmonic generation (SHG) in an optical nanocircuit is proposed. We demonstrate both theoretically and experimentally that the symmetry of an optical mode alone is sufficient to allow SHG even in centro-symmetric structures made of centro-symmetric material. The concept is realized using a plasmonic two-wire transmission-line (TWTL), which simultaneously supports a symmetric and an antisymmetric mode. We first confirm that emission of second-harmonic light into the symmetric mode of the waveguide is symmetry-allowed when the fundamental excited waveguide modes are either purely symmetric or antisymmetric. We further switch the emission into the antisymmetric mode when a controlled mixture of the fundamental modes is excited simultaneously. Our results open up a new degree of freedom into the designs of nonlinear optical components and should pave a new avenue toward multifunctional nanophotonic circuitry.

Ernst Lecher and his wires

This paper focuses on Ernst Lecher, Austrian physicist, who studied guided electromagnetic propagation on two parallel wires, with the aim of measuring the relative wavelength. He perfected this device up to the point that "Lecher lines" become a synonym for a two-wire transmission line. His findings were used throughout all of the XXth century to tune UHF receivers, and are still used as an educational tool.

Reversible Mapping and Sorting the Spin of Photons on the Nanoscale: A Spin-Optical Nanodevice.

The photon spin is an important resource for quantum information processing as is the electron spin in spintronics. However, for subwavelength confined optical excitations, polarization as a global property of a mode cannot be defined. Here, we show that any polarization state of a plane-wave photon can reversibly be mapped to a pseudospin embodied by the two fundamental modes of a subwavelength plasmonic two-wire transmission line. We design a device in which this pseudospin evolves in a well-defined fashion throughout the device reminiscent of the evolution of photon polarization in a birefringent medium and the behavior of electron spins in the channel of a spin field-effect transistor. The significance of this pseudospin is enriched by the fact that it is subject to spin-orbit locking. Combined with optically active materials to exert external control over the pseudospin precession, our findings could enable spin-optical transistors, that is, the routing and processing of quantum information with light on a subwavelength scale.

A Single-Crystalline Silver Plasmonic Circuit for Visible Quantum Emitters.

Plasmonic waveguides are key elements in nanophotonic devices, serving as optical interconnects between nanoscale light sources and detectors. Multimode operation in plasmonic two-wire transmission lines promises important degrees of freedom for near-field manipulation and information encoding. However, highly confined plasmon propagation along gold nanostructures is typically limited to the near-infrared region due to ohmic losses, excluding all visible quantum emitters from plasmonic circuitry. We report on the top-down fabrication of complex plasmonic nanostructures in single-crystalline silver plates. We demonstrate the controlled remote excitation of a small ensemble of fluorophores by a set of waveguide modes and the emission of the visible luminescence into the waveguide with high efficiency. This approach opens up the study of a nanoscale light-matter interaction between complex plasmonic waveguides and a large variety of quantum emitters available in the visible spectral range.

On the Radiated Susceptibility of a Two-Wire Transmission Line Under Near- and Far-Field Conditions

An analytical transmission line (TL) coupling model is presented for evaluating the deviation between the susceptibility of a DUT in the near- and far-field of a noise source. Appropriate field solutions of elementary antennas are used in combination with coupling equations of an electrically short two-wire TL. A normalized coupling is defined to quantify the difference between the near- and far-field disturbances. It is found that the field coverage and the wave impedance of the radiating source are the dominant factors. The evaluation of the normalized coupling voltage results in potential deviations up to an order of magnitude. Therefore, it is concluded that standard EMC-test in the far-field may not always reflect the coupling level under different realistic circumstances appropriately. The analytical model is validated by accurate three dimensional field simulations and experiments.

Liquids Permittivity Measurement Using Two-Wire Transmission Line Sensor

A novel method for the measurement of complex permittivity of liquid dielectric materials in a wide frequency range is proposed. The technique utilizes an open-ended two-wire transmission line sensor that is submerged in a liquid-under-test to determine its complex permittivity from the measured differential reflection coefficient. The proposed approach has been theoretically analyzed to derive the appropriate sensor’s model and the required calibration procedure as well as experimentally validated by measurements of three liquids having frequency-dependent complex permittivity. Moreover, measurement accuracy analysis has been provided, including the method‘s uncertainty estimation and error sources’ discussion. Finally, the measured permittivity of each liquid has been compared against tabularized data. Good agreement has been obtained proving the validity and applicability of the proposed method.

Dual-band transmission polarization converter based on planar-dipole pair frequency selective surface

A novel linear polarization converter operating in C- and X-bands with high polarization conversion ratio is described and demonstrated based on frequency selective surface. The building element is a planar-dipole pair, which is orthogonally printed on a double-layer substrate and vertically connected by a pair of through-via holes functioning as a quasi-two-wire transmission line coupler. A perforated metal shielding layer is sandwiched between the double-layer structure to only support a transverse electric and magnetic (TEM) mode coupling between the top and bottom dipolar components. The front dipole responds to the incident transverse electric (TE) wave, and sends the induced current into the two-wire transmission line to feed the bottom dipole. The bottom dipole is orthogonal or oriented at an arbitrary angle with respect to the top one, and a resultant outgoing transverse magnetic (TM) wave or arbitrary orientation polarized wave can be achieved. In addition, a bidirectional orthogonal polarization converter is realized by using double orthogonally arranged planar-dipole pairs, which are also printed on the same double-layer substrate.

Analytical Approximation for the Inductance of Circularly Cylindrical Two-Wire Transmission Lines with Proximity Effect

The paper describes a simple analytical approximation for the inductance of two-wire transmission lines of circularly cylindrical wires with proximity effect. It yields precise results up to very high frequencies, and also at all interaxial distances between the wires above some limit. Its accuracy is established by comparison to numerical computations and to measurements. It is shown that the proximity effect cannot be neglected unless the interaxial distance between the wires amounts to at least four wire diameters. Further, images of the current distribution in various situations are discussed.

Limits of Kirchhoff\u2019s Laws in Plasmonics

The validity of Kirchhoff’s laws in plasmonic nanocircuitry is investigated by studying a junction of plasmonic two-wire transmission lines. We find that Kirchhoff’s laws are valid for sufficiently small values of a phenomenological parameter κ relating the geometrical parameters of the transmission line with the effective wavelength of the guided mode. Beyond such regime, for large values of the phenomenological parameter, increasing deviations occur and the equivalent impedance description (Kirchhoff’s laws) can only provide rough, but nevertheless useful, guidelines for the design of more complex plasmonic circuitry. As an example we investigate a system composed of a two-wire transmission line and a nanoantenna as the load. By addition of a parallel stub designed according to Kirchhoff’s laws we achieve maximum signal transfer to the nanoantenna.