Electromagnetic Coupling Mechanism Research Articles

다층 지하 구조물로의 고고도 전자기파(HEMP) 커플링 현상에 대한 전자기적 모델링

본 논문에서는 다층 지하 구조물로의 고고도 전자기파(high altitude electromagnetic pulse: HEMP)의 커플링 현상을 분석하였다. 이를 위하여, 고고도 전자기파에 대한 모델링을 통하여, 고고도 전자기파의 스펙트럼이 100 MHz 이상의 대역에서 -30 dB 이하로 급격히 감소함을 확인하였다. 또한, 고고도 전자기파의 커플링 영역인 다층 지하 구조물은 지구의 표면과 내부를 구성하는 5층 구조물로 가정하여, 본 구조물을 구성하는 물질의 전파 상수(propagation constant)를 바탕으로 투과 현상을 분석하였다. 그 결과, 50 kV/m의 평면파를 입사시켰을 때, 지상에서 100 m 깊이에 위치한 지하 터널에서 0.1 MHz와 1 MHz의 평면파에 대하여 각각 약 10 kV/m와 5 kV/m의 투과 현상이 발생함을 확인하였다. 투과된 전기장의 효과적인 차폐 효과 확보를 위하여 토양층의 감쇠 상수(attenuation constant)를 이용한 자연 차폐 방법과 금속 격자 구조물의 필터링(filtering) 현상을 이용한 차폐 방법을 통하여 각각 최대 20 dB와 90 dB의 차폐 효과를 얻을 수 있음을 분석하였다. This paper gives a electromagnetic coupling mechanism of the high altitude electromagnetic pulse (HEMP) into large- scale underground multilayer structures using analytic and numerical methods. The modeling methods are firstly addressed to the HEMP source which can be generated by intentional nuclear explosion. The instantaneous and intense electromagnetic pulse of the HEMP source is concerned from DC to 100 MHz band, because the power spectrum of the HEMP is rapidly decreased under -30 dB over the 100 MHz band. Through this range, a penetrated electric field distribution is computed within the large-scale underground multilayer structures. As a result, the penetrated electric field intensities at 0.1 and 1 MHz are about 10 and 5 kV/m, respectively. Therefore, additional shielding techniques are introduced to protect buried structures within the large-scale underground structures such as high-lossy material and filtering structures (wire screen).

Design and Implementation of Noble Metal Nanoparticle Cluster Arrays for Plasmon Enhanced Biosensing.

Nanoparticle Cluster Arrays (NCAs) are a class of electromagnetic materials that comprise chemically defined nanoparticles assembled into clusters of defined size in an extended deterministic arrangement. NCAs are fabricated through integration of chemically synthesized building blocks into predefined patterns using a hybrid top-down/bottom-up fabrication approach that overcomes some of the limitations of conventional top-down fabrication methods with regard to minimum available feature size and structural complexity. NCAs can sustain near-field interactions between nanoparticles within individual clusters as well as between entire neighboring clusters. The availability of near-field interactions on multiple length scales - together with the ability to further enhance the coupled plasmon modes through photonic modes in carefully designed array morphologies - leads to a multiscale cascade electromagnetic field enhancement throughout the array. This feature article introduces the design and fabrication fundamentals of NCAs and characterizes the electromagnetic coupling mechanisms in the arrays. Furthermore, it reviews how the optical properties of NCAs can be tuned through the size and shape of the nanoparticle building blocks and the geometry, size, and separation of the assembled clusters. NCAs have potential applications in many different areas; this feature article focuses on plasmon enhanced biosensing and surface enhanced Raman spectroscopy (SERS), in particular.

Equivalent damping and frequency change for linear and nonlinear hybrid vibrational energy harvesting systems

A unified approximation method is derived to illustrate the effect of electro-mechanical coupling on vibration-based energy harvesting systems caused by variations in damping ratio and excitation frequency of the mechanical subsystem. Vibrational energy harvesters are electro-mechanical systems that generate power from the ambient oscillations. Typically vibration-based energy harvesters employ a mechanical subsystem tuned to resonate with ambient oscillations. The piezoelectric or electromagnetic coupling mechanisms utilized in energy harvesters, transfers some energy from the mechanical subsystem and converts it to an electric energy. Recently the focus of energy harvesting community has shifted toward nonlinear energy harvesters that are less sensitive to the frequency of ambient vibrations. We consider the general class of hybrid energy harvesters that use both piezoelectric and electromagnetic energy harvesting mechanisms. Through using perturbation methods for low amplitude oscillations and numerical integration for large amplitude vibrations we establish a unified approximation method for linear, softly nonlinear, and bi-stable nonlinear energy harvesters. The method quantifies equivalent changes in damping and excitation frequency of the mechanical subsystem that resembles the backward coupling from energy harvesting. We investigate a novel nonlinear hybrid energy harvester as a case study of the proposed method. The approximation method is accurate, provides an intuitive explanation for backward coupling effects and in some cases reduces the computational efforts by an order of magnitude.

Coupling of a Tl2Ba2CaCu2O8 Thin Film Intrinsic Josephson Junction and a Fabry—Perot Resonator

We study the electromagnetic coupling mechanism of a Tl2Ba2CaCu2O8 (Tl-2212) thin film intrinsic Josephson junction to a hemispherical Fabry—Perot resonator. An effective model to analyze coupling mechanism is put forward. The dielectric substrate is used as a dielectric resonator antenna and the Josephson junction, and a superconducting film is used as the feed line to excite a resonance mode inside the dielectric resonator antenna. To confirm this method, two Josephson junction samples with different dimensions of substrate and shapes of superconducting film are fabricated and tested under microwave irradiations. At the same time, numerical simulations of the antenna characteristics and the field distribution of these samples are performed by numerical simulation. The different coupling intensities of the two samples with the Fabry—Perot resonator fit well with the numerical simulation results. The proposed model is important for Josephson junctions used in the microwave field.

EMC Issues in High-Power Grid-Connected Photovoltaic Plants

This paper outlines the main electromagnetic compatibility issues frequently encountered in high-power grid-connected photovoltaic (PV) systems, and proposes several guidelines that allow to obtain an effective and highly efficient layout of the plant. At first, with reference to a 1-MWp PV plant of Sorgenia Solar, Italy, the paper focuses on the peculiar aspects concerning the radio-frequency behavior of a large-size PV plant: the great extent of the direct-current cabling, the capacitance toward earth of the PV source, the common-mode (CM) disturbance generated by inverters, the galvanic isolation ensured by dedicated low-voltage power transformers, and the presence of resonant circuits for CM leakage currents. The dominant electromagnetic phenomena and coupling mechanisms are pointed out by means of an equivalent circuit and through measurements. In the light of the matured experience, several guidelines are proposed and a new reliable layout is implemented on a second 1-MWp PV plant. New measurements confirm the validity of the proposed design strategy.

Fluorescence relaxation in the near–field of a mesoscopic metallic particle: distance dependence and role of plasmon modes

We analytically and numerically analyze the fluorescence decay rate of a quantum emitter placed in the vicinity of a spherical metallic particle of mesoscopic size (i.e with dimensions comparable to the emission wavelength). We discuss the efficiency of the radiative decay rate and non-radiative coupling to the particle as well as their distance dependence. The electromagnetic coupling mechanisms between the emitter and the particle are investigated by analyzing the role of the plasmon modes and their nature (dipole, multipole or interface mode). We demonstrate that near-field coupling can be expressed in a simple form verifying the optical theorem for each particle modes.

Coupling mechanism of an EMAT

Electro-magnetic acoustic transducers (EMATs) generate ultrasonic waves in metals through an electromagnetic coupling mechanism. A concept for EMAT generation, using a coil alone without a permanent magnet, but with a pulse generator and a sample, is introduced. A simplified equivalent coil circuit is given, and has been validated by experimental measurements. Such an equivalent circuit is useful for excitation current calculations, which have often been neglected in previous publications in this area but have proved to be of great importance in considering the efficiency and frequency characteristics of ultrasonic generation. Due to the coil sample coupling, the equivalent coil inductance is dependent on the electrical conductivity and magnetic permeability of the metal sample, the lift-off, the coil orientation relative to the metal sample and the coil configuration. The use of a coil alone to generate ultrasound has limited applications as a suitable ultrasonic detector must also be used, but where appropriate this type of generation source provides a robust, non-contact and inexpensive means of ultrasonic generation without worrying the permanent magnet attracting ferromagnetic particles that can prevent from practical on-line application of EMATs.

Coupling mechanism of electromagnetic acoustical transducers for ultrasonic generation

Electromagnetic acoustic transducers (EMATs) generate ultrasonic waves in metals through an electromagnetic coupling mechanism. A concept for EMAT generation, using a coil alone without a permanent magnet, but with a pulse generator and a sample, is introduced. A simplified equivalent coil circuit is given and has been validated by experimental measurements. Such an equivalent circuit can be used for variations in excitation current calculations, which have often been neglected in previous publications in this area but have proved to be of great importance in considering the efficiency and frequency characteristics of ultrasonic generation. The equivalent coil inductance is dependent on the distance between the coil and the sample, due to coil interactions with eddy currents and the Ampere current of the magnetization mechanism. Analytical solution for an annular coil above metal samples is given, and the influences of the lift-off, coil radius, material magnetic permeability and electrical conductivity on the equivalent coil inductance are discussed. Experimental measurements agree well with predictions.

Electromagnetic coupling mechanism to a conducting strip through a narrow slit in a parallel-plate waveguide

The problem of electromagnetic coupling to a conducting strip through a narrow slit in a parallel-plate waveguide (PPW) is reconsidered with an emphasis on the radiative coupling mechanism. Two different types of coupling are discussed: cavity and parasitic. The maximum coupled power in both cases is observed to be almost the maximum available power from the slit (half of the incident power in the PPW), even though the two types of coupling are quite different from each other in their equivalent circuit representation or coupling mechanism. The similarity between the problem of cavity-type coupling and the previously reported transmission resonance problem through a narrow slit in thick screens is also described in connection with the aperture-body resonance phenomenon.

Distinguishing Alfvén waves from quasi‐static field structures associated with the discrete aurora: Sounding rocket and HILAT satellite measurements

We present and analyze sounding rocket and HILAT satellite measurements of the low frequency (< 1 Hz) electric and magnetic fields δE and δB perpendicular to the Earth's magnetic field B0 in the auroral oval. By examining the time‐domain field data it is often difficult to distinguish temporal fluctuations from static structures which are Doppler shifted to a non‐zero frequency in the spacecraft frame. However, we show that such a distinction can be made by constructing the impedance function Z(f) = μ0|δE(f)/δB(f)|. Using Z(f) we find agreement with the static field interpretation below about 0.1 Hz in the spacecraft frame, i.e. Z(f) = Σp−1 where Σp is the height‐integrated Pedersen conductivity of the ionosphere. Above 0.1 Hz we find Z(f) > Σp−1, which we argue to be due to the presence of Alfvén waves incident from the magnetosphere and reflecting from the lower ionosphere, forming a standing wave pattern. These waves may represent an electromagnetic coupling mechanism between the auroral acceleration region and the ionosphere.