Hyun Ho Park

Electromagnetic penetration into a rectangular cavity with multiple rectangular apertures in a conducting plane

Electromagnetic wave penetration into a rectangular cavity with multiple rectangular apertures is studied. The Fourier transform and the mode matching method are used to obtain simultaneous equations for the modal coefficients. The simultaneous equations are solved to represent the cavity field in series forms, which are suitable for numerical computations. Numerical computations are performed to investigate the field penetration into a cavity in terms of the shielding effectiveness for a various geometry.

Acoustic scattering from a rectangular aperture in a thick hard screen

Acoustic scattering from a rectangular aperture in a thick hard screen is examined. The Fourier transform is used to represent the scattered wave in the spectral domain and the boundary conditions are enforced to represent a solution in closed form. Numerical computations are performed to illustrate the behavior of the scattered wave from a thick rectangular aperture. The solution is represented in series which are numerically efficient.

An Effective and Efficient Approach for Radiated Emission Prediction Based on Amplitude-Only Near-Field Measurements

A new approach is proposed for modeling electromagnetic emissions of a printed circuit board (PCB) based on amplitude-only near-field measurement data. Magnetic dipoles placed over the top layer of the PCB are introduced as the equivalent of actual radiated sources. A restarted optimization procedure based on a differential evolution algorithm is developed to determine the parameters of the dipoles (number, position, and moment components) via minimizing the difference between the measured magnetic near field and that radiated by the dipoles. These equivalent dipoles can be used to predict the radiated emissions of the PCB once being determined. The proposed approach does not need the phase of the measured near fields, and its computational complexity is very low. Numerical results are presented to demonstrate the validity and efficiency of the proposed approach.

Design of a Resonant Reactive Shield With Double Coils and a Phase Shifter for Wireless Charging of Electric Vehicles

In this paper, a novel resonant reactive shield using a double-shield coil and phase-shift circuit is proposed to reduce magnetic field leakage in electric vehicle wireless charging applications. The double-reactive shield with a four-capacitor phase shifter generates a canceling magnetic field, the phase of which is perfectly opposite to that of the incident magnetic field, effectively reducing the leakage magnetic field as a result. The concept and structure, and an equivalent-circuit model analysis of the double-reactive shield are explained and discussed. The shielding effectiveness of the double-reactive shield is compared with that of a conventional reactive shield with a single-shield coil by a simulation and is verified by experiments.

Reduction of electromagnetic field (EMF) of wireless power transfer system using quadruple coil for laptop applications

In this paper, we proposed an effective coil design for electromagnetic field (EMF) noise reduction from the wireless power transfer system by using quadruple coils in transmitter and receiver for laptop computer application. By using quadruple coils for transmitter and receiver, EMF noise was significantly reduced with negligible change in induced voltage. 3D simulations and the field distributions are shown and the pros and cons are of the quadruple coil designs are discussed.

A Component-Level Radio-Frequency Interference Evaluation Method for Mobile Devices

In this letter, a radio-frequency interference (RFI) evaluation method for highly integrated mobile devices, such as smartphones and tablets, is proposed. A near-field specification for noise-emitting components in mobile devices is developed based on near-field emission measurements and RF sensitivity measurements of mobile devices with the bit-error-rate (BER) test. To devise the specification, a derivative relation between the near-field strength of noise sources and the system-level RF sensitivity is newly suggested using the theoretical relationship between the signal to interference and noise ratio and the probability of error in communication systems, and verified with empirical measurements. Using the proposed algorithm, an RFI evaluation specification for commercial camera modules widely used in modern smartphones was established at several RF communication bands.

A Simple Method of Estimating the Radiated Emission From a Cable Attached to a Mobile Device

When a mobile device is connected to cables for charging power or transmitting data, the radiated emission from the attached cables, which are typically effective electromagnetic interference (EMI) antennae at certain frequencies, can cause serious system-level EMI problems. The measurement of system-level radiation during compliance and precompliance tests is not only a time-consuming task, but also requires expensive facilities such as a semianechoic chamber. This paper proposes a simple method of predicting far-field radiation from cables attached to mobile devices at the early stage of the design and development phase without using an EMI chamber. The method combines radiation characterization of a simple box-source-cable geometry using full-wave simulations with the measurement of the real common-mode current flowing through the cable. The proposed method was applied to mobile phones to estimate the far-field radiated emissions, which were compared with the measurement results. The accuracy of the predicted results was evaluated using the feature selective validation technique, indicating good agreement and correlation.

Estimation of Power Switching Current by Chip-Package-PCB Cosimulation

This paper presents a methodology to estimate power switching current on printed circuit boards (PCBs) through chip-package-PCB cosimulation. A macromodel for a timing controller chip running pseudo H-pattern data was generated from transistor-level simulations. The macromodel consists of a passive impedance network and internal switching activity of the chip. Power delivery network models for package and PCB were produced as a RLCG netlist and S-parameter touch stone files, respectively, using commercial tools. It is found that comparison between the simulated and measured impedances of the chip and package shows excellent agreement up to 300 MHz. Also, the simulated and measured impedances of the PCB match well in terms of magnitude and resonance frequency up to 3 GHz. Moreover, the results of power switching current from cosimulation and measurement show good agreement within 5 dB difference at major harmonic frequencies of 20 MHz data and 80 MHz clock patterns up to 1 GHz.

Magnetic Shielding Analysis of a Slit on a Conducting Plate Coated With a Ferrite Sheet: Transverse Incidence

In this paper, an analytical solution is presented for magnetic shielding analysis of a slit on a conducting plate coated with a ferrite sheet. The Fourier transform and the mode matching technique are employed to obtain the analytical solution for magnetic vector potential. Magnetic shielding effectiveness is investigated in terms of the geometrical parameters of a slit on a conducting plate and a ferrite sheet. The proposed method is numerically validated by a commercial finite element solver with good agreement. In addition, the proposed analytical solution is in a rapidly converging series so that it is more efficient than other numerical techniques.

An indoor location tracking based on mobile RFID for smart exhibition service

Recently, various smart application services have been developed using GPS (Global Positioning System), RFID (Radio Frequency IDentification) and sensor networks. The GPS has been successfully applied for outdoor location tracking by many applications, but it might still be insufficient in an indoor environment where GPS signals are often severely obstructed. The RFID technology has been utilized to play an important role in location tracking for indoor smart applications. Therefore, in this paper, we present the scenario and architecture of an indoor location tracking service for things or space in an exhibition environment based on mobile RFID. The RFID tags of things or spaces are identified as the locations of point being passed and we obtain the spatial data from the tags using mobile RFID readers, Web server and Database server. We have designed and implemented the prototype of location tracking system for exhibition scenario using Microsoft .NET framework. Additionally, we have verified the functionality of this system so various other indoor smart services may be provided using the proposed system.