Transverse Electromagnetic Research Articles

Dual-Beam Periodic Leaky-Wave Antenna With Reduced Beam Squinting

In this letter, a dual-beam periodic leaky-wave antenna with a low beam-squinting character is presented. It has a simple and low-profile configuration, which consists of 15 slot radiating elements and one microstrip feedline. The slot radiating element creates nulls in the pattern at forward and backward endfire. By properly arranging the radiating elements with a small separation, the higher order spatial harmonics are suppressed. Fed by an air-substrate microstrip line working on the non-dispersion transverse electromagnetic (TEM) mode, the antenna has a moderate phase constant leading to a stable endfire array factor. By integrating the almost unchanged array factor and element pattern, the dual-beam radiation pattern with reduced beam squinting is obtained. To verify the design strategy, a prototype was designed, fabricated, and measured. Over the operating bandwidth from 2.7 to 3.2 GHz, the antenna exhibits a small measured beam squint of 6.8°.

1-D Frequency-Diverse Single-Shot Guided-Wave Imaging Using Surface-Wave Goubau Line

This article presents a 1-D frequency-diverse guided-wave imaging technique based on a surface-wave Goubau line. It employs frequency diversity to capture spatial information of the scatterers with an almost real-time speed, which is much faster than mechanical scanning or electronic scanning approaches. The surface-wave Goubau line is used because it provides more independent measurement modes than conventional transverse electromagnetic (TEM) transmission lines. Compressed sensing algorithms are employed to recover the spatial distributions when some sparse metal scatterers are placed above the line. The proposed technique is validated by four numerical examples and two experimental validations, where both narrow scatterers and wide scatterers are considered. It shows that the proposed technique is able to reconstruct scatterer position within an error of 1 mm, about 1/30 space wavelength at the center frequency 10 GHz. It is also able to identify two close scatterers until their distance reduces to 1 mm. This guided-wave technique, although applicable to very near-field detection only, can find broad applications in localization, field measurement, and fault detection.

Ku-Band Radial-Line Continuous Transverse Stub Antenna With Transmit-Array Lens for High-Power Microwave Application

An antenna operating at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band for high-power microwave (HPM) applications is presented in this article. The antenna can realize directional radiation of the coaxial transverse electromagnetic (TEM) mode and form a pencil beam in the desired direction. The antenna contains two parts: a radial-line continuous transverse stub antenna (RL-CTSA) as a feed antenna and two transmit-array (T-A) lenses. The RL-CTSA is designed to be a standing wave antenna, and the CTSA is step sized and arranged concentrically on the antenna aperture. The T-A lens consists of numerous elliptical-hole elements and can achieve a full transmission phase of 360° by rotating the elliptical-hole elements. An antenna prototype operating at 14.25 GHz has been designed and fabricated with an aperture radius of 300 mm. The experimental results show that the antenna has a gain of 37.9 dBi with a 21° deflection in elevation plane. The aperture efficiency reaches 75.1%, the reflectance is below −20 dB, and the radiation efficiency is more than 94.0%. Furthermore, high-power tests indicate that the power handling capacity of the antenna is higher than 250 MW.

Hall-Effect Current Sensors Susceptibility to EMI: Experimental Study

The paper deals with the susceptibility to Electromagnetic Interference (EMI) of Hall-effect current sensors. They are usually employed in power systems because of their galvanic isolation. The EMI robustness of such contactless device was compared with that of resistive current sensing (wired method). To this purpose, a printed circuit board (PCB) was fabricated. EMI tests methods such as Bulk Current Injection (BCI), Transverse-Electromagnetic (TEM) cell and Direct Power injection (DPI) were performed to evaluate the robustness of the Hall-Effect current sensor. EMI-induced failures are highlighted by comparing the different measurements tests and setups.

A Predictive Model for Multipactor Discharge in Coaxial Systems Based on Chaos Theory

Multipactor is an electron discharge driven by secondary electron emission (SEE). Recently, a novel theoretical approach for multipactor based on principles from nonlinear dynamics and chaos theory has been introduced and applied to a parallel-plate geometry. In this article, the theory is extended to a coaxial geometry driven by the fundamental transverse electromagnetic (TEM) mode and an axial dc magnetic field. This configuration is often examined in light of multipactor suppression schemes for space-borne applications. Maps that relate the radio frequency (RF) emission phase to the RF arrival phase are developed for both the inner and outer conductors with no a priori assumptions on the electron trajectories (neglecting space-charge effects). By combining the system attractors with secondary emission properties of the conductor material, multipactor growth (or decay) is predicted throughout parameter space under realistic spreads in secondary emission energies and angles. This model is validated against published simulation and experimental results.

Perturbations of Electric and Magnetic Fields Due to the Presence of Materials in TEM Cells

This paper investigates in detail the impact of electric (E) and magnetic (H) field distributions inside transverse electromagnetic (TEM) cells, below and above the corresponding dominant modes of the cells, in conditions differing from free space, i.e., in presence of representative ferromagnetic and dielectric materials. Simulations and measurements are performed from hundreds of MHz to GHz using IEC 61967-2 (closed) and open TEM cells. Whatever the frequency and equipment under test location, unlike dielectric material, which only locally changes the norms (||.||) of E (and H depending on permittivity) at its location, the presence of ferromagnetic material inside the cell changes both ||E|| and ||H|| distributions: locally below the dominant mode frequency and globally at the entire bottom of the cell above that frequency. This demonstrates that a local distortion of ||H||-field, due to ferromagnetic material, has a stronger influence than a local distortion of ||E||-field, disregarding frequency, location, and magnetic losses. Moreover, the demand to use a TEM cell below the dominant mode frequency, as mentioned in the IEC 61967-2 and 62132-2 standards, may not be relevant, provided that both electromagnetic field inhomogeneities are considered, and the presence of an integrated circuit package in the cell is accounted for in the equivalent ||E||-field level around the pins in immunity testing.

Radiation from free space TEM transmission lines

This work derives exact expressions for the radiation from two conductors non-isolated transverse electromagnetic (TEM) transmission lines of any small electric size cross-section in free space. The cases of infinite, semi infinite and finite transmission lines are covered and it is shown that while an infinite transmission line does not radiate, there is a smooth transition between the radiation from a finite to a semi-infinite transmission line. The present analysis is in the frequency domain and the authors consider transmission lines carrying any combination of forward and backward waves. The analytic results are validated by successful comparison with ANSYS commercial software simulation results, and successful comparisons with other published results.

Extracting the Electromagnetic Radiated Emission Source of an Integrated Circuit by Rotating the Test Board in a TEM Cell Measurement

In this paper, the radiated emission of a microcontroller integrated circuit is investigated by rotating the test board in a transverse electromagnetic (TEM) cell measurement. The dependence of the radiated emission on the angle of rotation is derived on the basis of the coupling between a microstrip line and the TEM cell, and then validated by the multiple-orientation TEM cell measurements in a quantitative accuracy of fitting. With the validated dependence, the radiated emissions contributed by electric and magnetic coupling are extracted. The extracted emissions are found in agreement with the measurement result by near-field scanning experiments.

Determining the effect of relative size of sensor on calibration accuracy of TEM cells

The time-domain calibration coefficient of a D-Dot sensor should be identical across various transverse electromagnetic (TEM) cells to comply with the IEEE Std 1309. However, in our previous calibration experiments, poor consistency was observed. The size of D-Dot sensors relative to TEM cells is considered the main reason for this poor consistency. Therefore, this study aims at determining the calibration coefficient of a D-Dot sensor. We calculate the theoretical coefficient as a reference. Practical calibration experiments involve the processing of TEM cells with three different sizes. To observe the response more clearly, corresponding models are constructed and numerical simulations are performed. The numerical simulations and experimental calibration are in good agreement. To determine the calibration accuracy, we quantify the accuracy using the relative error of the calibration coefficient. By comparing the coefficients obtained, it can be concluded that the perturbation error is about 15% when the relative size is over 1/3. Further, the relative size should be less than 1/5 to obtain a relative error below 10%.

A Novel Passive Cost-Effective Technique to Improve Radiated Immunity on PCBs

This paper proposes a novel simple cost-effective technique to improve the potential immunity of integrated circuits (ICs) to radiated electromagnetic (EM) disturbances. It is based on dielectric loading which lessens the susceptibility of ICs independently of frequency by confining the reactive fields inside the dielectric load. This has no side effects on the IC performance. To highlight the importance of the proposed technique, immunity testing was performed numerically both in near and far fields. A loaded IC (a microcontroller) was compared to an unloaded one through far-field measurements inside a transverse EM cell to indirectly assess the suitability of the proposed approach. Results show that loading the IC with non-ferromagnetic dielectric material not only effectively decreases its susceptibility to electric field, but also to magnetic field. Moreover, a significant difference of $\sim$ 48% less failure rate was achieved for the loaded compared to the unloaded IC demonstrating the usefulness of this technique as a potential solution for radiated immunity improvement.

Self-focusing of higher-order asymmetric elegant Hermite-cosh-Gaussian laser beams in collisionless magnetized plasma

In the present paper, we have explored the complexity in self-focusing of asymmetric elegant Hermite-cosh-Gaussian (EHChG) laser beams in magnetized plasmas. We have studied transverse electromagnetic (TEM) mode indices (m, n) of laser with distinct values (0, 0), (0, 2) and (0, 4). The nonlinearity in dielectric constant considered herein is mainly due to the ponderomotive force. General form of differential equations for beam-width parameters in both transverse dimensions of the beam are established by using WKB and paraxial approximations through parabolic wave equation approach. The behaviour of beam-width parameters with dimensionless distance of propagation is studied at different parameters of plasma and those of the considered beams family.

The Reentrant Four-Layer Quasi-Elliptic Bandstop Filter

The novel microwave quasi-elliptic bandstop filter, which uses the initially uncoupled strip transmission lines, is considered in this work. The proposed filter is based on the reentrant structure, where the metallic body with a floating potential is asymmetric. Generally speaking, the internal and external dielectric fillings must have their unequal relative permittivities. As a result, additional symmetrical reflection zeros are reached at the lower and upper pass bands of the stop band leading to the quasi-elliptic function response that improves the filter selectivity. The general transverse electromagnetic (TEM) circuit model for the proposed filter in terms of a series connection of the multi-ports is presented and then used to predict the initial electrical and geometrical parameters. An experimental printed circuit prototype has been manufactured and evaluated to validate the design concept. The measured filter parameters correlate well with the simulation-derived ones and that increases the degree of freedom in the fabrication of microwave frequency selective components.

A 3‐D Printed PCB Integrated TEM Horn Antenna

AbstractThis paper presents a very broadband (5–40 GHz) novel three dimension (3‐D) printed Transverse ElectroMagnetic (TEM) horn antenna. It is integrated with a planar Printed Circuit Board and radiates in a perpendicular direction of the Printed Circuit Board. The described antenna provides benefits in terms of cost and size for a two dimensional antenna array. Here the antenna and its corresponding transition to a regular 50 Ω microstrip line through Parallel Plate Waveguide and a 90° bend are presented. Prototypes of back‐to‐back transitions and antenna are fabricated and measured. The antenna has a return loss below −10 dB and a gain of approximately 10 dBi over the targeted frequency range.

Exact Solution for the Protected TEM Edge Mode in a PTD-Symmetric Parallel-Plate Waveguide

A Parity Time-reversal Dual (PTD) symmetric structure constituted by a Perfectly-Electric-Perfectly magnetic (PEC-PMC) parallel plate waveguide (PPW) is analyzed. This waveguide supports unimodal transverse electromagnetic (TEM) edge mode propagation protected against back-scattering from a certain class of deformations and defects. The TEM solution is found in analytical form by using three different methods, namely conformal mapping, mode-matching, and Fourier-transform methods. It is shown through numerical simulations that the mode propagation is robust with respect to deformations such as 90{\deg} bends and discontinuity such as transition to free-space. Implementation of the PMC boundary conditions via both a bed of nails and a mushroom structure is also successfully investigated.

Metaparticles of Pulsed Wave Fields

Properties of elementary particles of pulsed (localized) electromagnetic and acoustic wave fields directionally radiated by aperture sources (antennas, lasers, acoustic diaphragms) in free space and homogeneous isotropic media, for which the term metaparticle is used, are considered. The structure of the wave field and the energy transferred by the metaparticles are presented. The results obtained for the presented scalar theory of metaparticles of pulsed transverse electromagnetic (TEM) waves and longitudinal elastic acoustic waves can be extended to vector pulsed wave modes guided by layered inhomogeneous guiding media and guiding technical devices (waveguides).

Octagonal Shaped Metamaterial Absorber Based Energy Harvester

In this study, a novel octagonal shaped metamaterial based broadband absorber is proposed for energy harvesting at WIMAX wireless communication band. The proposal has an absorption of 99.97 % at 5.5 GHz with a bandwidth of 1 GHz between 5 GHz and 6 GHz in Transverse Electric (TE) mode. Transverse Electric (TE), Transverse Magnetic (TM) and Transverse Electromagnetic (TEM) modes are studied numerically in this paper. In TM and TEM modes, proposed structure has absorption of nearly 96 % and 98 % respectively at 6 GHz. The proposed structure is polarization angle independent which is important for energy harvesting applications. Energy harvesting application is realized by using resistive loads on the design, simulations are parametrically studied on resistive loads and experimental study is realized for reflection coefficient measurement and compared with simulated results. Both experimental and simulated results are complying with each other. The proposed structure has different usage areas in stealth areas, detection and imaging. DOI: http://dx.doi.org/10.5755/j01.ms.24.3.18625

Design and experimental demonstration of a circularly polarized mode converter for high-power microwave applications.

A novel mode converter that can transform coaxial transverse electromagnetic (TEM) mode into circularly polarized TE11 (CPT) mode was developed and experimentally studied with high-power microwave (HPM). The mode conversion is realized by two steps. First, the TEM mode is converted into linearly polarized TE11 (LPT) mode by the webbed-shaped balun structure. Second, the LPT mode is transformed into the CPT mode with the insertion of circular-arc diaphragms in a circular waveguide. In this paper, the principle of a mode converter working at 1.57 GHz is demonstrated, as well as the experimental results. The experimental and simulation results are in good agreement. At the central frequency, the conversion efficiency is more than 99.5%, the measured axial ratio approximates to 1.39 dB, and the power handling capacity is in excess of 1.5 GW. These measured results meet the demand for narrow-band HPM source application.

Numerical Investigations of MRI RF-Induced Heating for External Fixation Device in TEM and Birdcage Body Coils at 3 T

This paper investigates the radio frequency (RF)-induced heating in American Society for Testing and Materials phantom with a generic external fixation device for both birdcage (BC) coil and transverse electromagnetic (TEM) coil. Two typical orientations, i.e., fixture bar perpendicular to and parallel to the coil axis, have been considered. To compare the specific absorption rate and temperature rise in the two different RF coils at 3 T, both electromagnetic and thermal simulations were performed. It is found that tibia external fixation device with orientation parallel to the coil axis will induce severe heating effect in both coils. However, pelvic external fixation device induces larger heating level in TEM coil than BC coil. Furthermore, increasing the pin length or pin spacing of the pelvic external fixation device will cause a larger heating level in TEM coil, while such changes have no substantial effects on BC coil. We show that the transversely distributed electric field in TEM coil forms the underlying reason why pelvic external fixation device induces a higher heating level in TEM coil than BC coil. This finding also indicates that metallic external fixation devices with large dimensions along transverse direction, while might be safe in BC coil, can experience significant heating issue in TEM coil.

Method to reduce an unwanted EM field component in a 4‐port TEM cell

As an alternative standard electromagnetic (EM) field generator, a 4-port TEM (transverse EM) cell can be used for an EM compatibility (EMC) emission and immunity test. However, unwanted EM fields generated in a TEM cell deteriorate the results and accuracy of critical EMC tests. A new method to suppress unwanted field components in a 4-port TEM cell is proposed. To reduce the unwanted EM field, the narrow slits in internal septa are inserted, which are transverse with respect to the direction of wave propagation. By introducing the slits, the 4-port TEM cell can provide improved standard EM field distribution with the much-lowered unwanted field component inside the usable test volume.

In brief

PAGE 488 Researchers in Korea fabricate a 4-port transverse electromagnetic (TEM) cell to suppress the generation of unwanted EM fields in typical TEM cell devices. The cell is made by introducing transverse slits in the septa of the device, which provide an alternative approach for electromagnetic compatibility (EMC) tests and measurements for many application fields. PAGE 515 A simple approach to improve the Q-factors of MIS capacitors is described in work from Korea. The low conductivity of silicon, as the lower electrode in capacitors, is improved by using a metal electroplating process and adding a Au metal coating. The simple coating process produces capacitors with Q-factors 25 % higher than conventional examples. A 4-port TEM cell for reducing unwanted electromagnetic fields in EMC testing and measurements. PAGE 517 Work from China introduces an analogue phase shifter that is designed to have a wide relative phase shift, low insertion loss and compact size. Simulations and measured results show that it is capable of efficient phase modulation for use in modern microwave systems. Metal electroplating is used to increase the Q factor of MIS capacitors. PAGE 476 Researchers in China propose a methodology for creating ultra-miniaturised frequency selective surfaces (FSSS). They have made single-band and dual-band FSSs with unit cell dimensions of (λ0/34) × (λ0/34) and (λ0/27) × (λ0/27), respectively. The advantages of ultra-miniaturisation, include independent control of filtering performance for different polarisations and extension of the multiband response. Designing phase shifters for modern microwave systems to have a low insertion loss and compact size. PAGE 519 Researchers in Brazil propose an analytical method to determine parameters of photovoltaic cells using explicit equations. The equations allow all parameters of the single diode model to be extracted from data that is provided in photovoltaic panel datasheets. The method is shown to give superior results with lower errors than other reported analytical methods. A methodology for producing single-band and dual-band ultra-miniaturised frequency selective surfaces. Low errors with an analytical method to determine parameters of photovoltaic cells.