Jae-Hoon Yun

Effects of combined radiofrequency radiation exposure on the cell cycle and its regulatory proteins.

The aim of this study was to investigate whether single or combined radio frequency (RF) radiation exposure has effects on the cell cycle and its regulatory proteins. Exposure of MCF7 cells to either single (837 MHz) or combined (837 and 1950 MHz) RF radiation was conducted at specific absorption rate values of 4 W/kg for 1 h. During the exposure period, the chamber was made isothermal by circulating water through the cavity. After RF radiation exposure, DNA synthesis rate and cell cycle distribution were assessed. The levels of cell cycle regulatory proteins, p53, p21, cyclins, and cyclin-dependent kinases were also examined. The positive control group was exposed to 0.5 and 4 Gy doses of ionizing radiation (IR) and showed changes in DNA synthesis and cell cycle distribution. The levels of p53, p21, cyclin A, cyclin B1, and cyclin D1 were also affected by IR exposure. In contrast to the IR-exposed group, neither the single RF radiation- nor the combined RF radiation-exposed group elicited alterations in DNA synthesis, cell cycle distribution, and levels of cell cycle regulatory proteins. These results indicate that neither single nor combined RF radiation affect cell cycle progression.

Antenna Measurement Method in Fresnel Region by

The far-field pattern and gain obtained using the far-field measurement method can be highly accurate when the distance between the source antenna and the antenna under test (AUT) satisfies the Rayleigh far-field criterion. In this letter, we propose an improved Fresnel region measurement method that can be applied in a shortened distance between two antennas. The many Fresnel fields required are captured by changing angle phi of the scanning plane. This scanning involves rotating the roll positioners of the source antenna and the AUT in the same direction and by the same amount, and rotating the azimuth positioner in the horizontal plane. The radiation pattern and gain from the simulation and experimental measurements agreed closely with the reference far-field pattern and gain. The proposed antenna measurement method in Fresnel region by phi-variation scanning can be easily applied to most popular far-field measurement systems without any additional cost.

\phi

In this letter, we designed and fabricated a broadband probe with a double-ridged waveguide for broadband near-field measurements. An exponentially tapered ridge in the rectangular waveguide and a novel waveguide transition were used for broadband impedance matching and suppression of higher order modes. The probe has broadband characteristics and its measured impedance bandwidth is approximately 123% (4.17:1) in the range 12.0-50 GHz for standing wave ratios (SWR) <3.0. The peak radiation gain range and nominal radar cross-section (RCS) are 5.7-14.3 dBi and -30 dBsm, respectively. The performance of this probe was verified using the measured results and is in good agreement with the simulated results.

-Variation Scanning

In this letter, we propose a new method to predict the field at the finite distance from a source antenna. The Fresnel fields measured using a far-field measurement system are transformed into the Fresnel or finite-distance far field, after multiplying with a weighting factor. To check the validity of this method, we compared the results with a simulated aperture antenna with uniform current distribution, as well as with an actual horn antenna. The transformed patterns agreed closely with the exact field patterns. The proposed method is very useful for predicting the electromagnetic field located out of chamber range in a far-field measurement system.

The Design of Broadband Probe for Efficient Near Field Measurements

This paper describes a new optical link system which consists of a metal optical bench, a module printed circuit board, a driver/receiver integrated circuit, a vertical-cavity surface-emitting laser/photo diode (VCSEL/PD) array, and an optical link block with plastic optical fibers for reducing electromagnetic interference (EMI) noise. For the optical interconnection between the light-sources and detectors, an optical wiring method whose distinctive features include the absence of EMI noise and easy assembly is proposed. The results clearly demonstrate that the use of an optical wiring method can provide robust, cost-effective assembly and easy-repair. We successfully achieved a 4.5 Gb/s data transmission rate without EMI problems.

New Method for Predicting the Electromagnetic Field at a Finite Distance Using Fresnel Field Transformation

This paper designes an optimized straight CTL cell whose uniform area is 20 mm × 20 mm and generates the dominant E-field and H-field to calibrate small EM field probes by using a wideband balun and a wideband power divider. The fabricated optimized straight CTL cell can operate on the broadband frequency range up to 2800 MHz except 2170 MHz. The fabricated two baluns, low frequency band balun and high frequency band balun, that consisted of a divider and two 3-dB quadrature coupler within 0.27 dB of the amplitude difference and 180 ±2.6° of the phase difference from 800 to 3000 MHz. And, the fabricated two power divider use the 3-section Wilkinson power divider type. The field uniformity of the uniform area in the fabricated optimized straight CTL cell is within +1 dB. The measured dominant E & H-field and resonant frequencies of the designed CTL cell agree well with the simulated results.

Optical Chip-to-Chip Link System by Using Optical Wiring Method for Reducing EMI

The author describes an optimized straight CTL cell whose uniform area is 2cm times 2cm and field uniformity is plusmn1 dB to calibrate small EM field probes in air. We could obtain the cell with the broadband frequency range up to 2.1 GHz. The field uniformity and frequency range of the cell are compared with those of square type CTL cell and symmetric TEM cell with same test zone in this paper. It is shown that the optimized CTL cell can provide the standard EM fields with broadband frequency range. The measured electric fields and resonant frequencies of the designed CTL cell agree well with the simulated results by moment methods (MM) and variational method (VM) respectively

The dominant E-field generation in the optimized straight CTL cell by using a wideband balun

Conventional polarizers usually include complicated corrugations and lossy insertions such as an iris, septa and dielectric slab, causing performance degradation and fabrication difficulties. At high frequencies, such fabrication difficulties and lossy components are limiting factors to achieving low costs and high performance. In this paper, a novel waveguide-type polarizer with an oval shaped cross-section that is inclined at a ± 45° angle for right-handed and left-handed circular polarization is presented. Due to the oval cross-section, the polarizer can be easily fabricated by mechanical processing with considerable performance. The proposed polarizer structure is fabricated using a pyramidal horn with a square aperture. From measured results, it is confirmed that the horn antenna has a gain of 9.4 dBi at 30.5 GHz with 20 dB cross-polarization level. The return loss is below -15 dB from 28 GHz to 34 GHz, and the axial ratio bandwidth is about 18% at a 3-dB level. This horn antenna will be applied to a feeder design with electrical beam scanning for a reflector-based mobile satellite antenna terminal.

Optimized straight CTL cell to calibrate EM field probes in air up to 2.1 GHz

The design method and analysis of novel broadband electromagnetic (EM) wave absorbers is presented in this paper. The proposed absorber is a planar structure based on lossy Electromagnetic Bandgap (EBG) surface with the specific sheet resistance, which replaces conventional resistive layer of Salisbury screen. The absorber performance can be easily controlled by simply modifying the EBG surface. The analysis for the reflectivity response due to the phase variation of the reflection and transmission recognizes electrical characteristics of the proposed absorber. A broadband reflectivity response with about 96% fractional bandwidth below -10 dB is presented. The computational results are presented to verify the functioning of the proposed absorber.

A Horn Antenna Design with Novel Waveguide Polarizer for Mobile Satellite Communications Applications

A practical optical rotary joint and optical links were prepared for an antenna measurement. The rotational variation loss of the optical rotary joint depends on the mechanical misalignments. To achieve 0.2 dB or less rotational variation loss, we proposed a new structure that has a noncontact interface using two size-mismatched fibers without a lens. The optical links are made of a distributed-feedback laser diode, a PIN-photodetector, and single-mode fiber jumper cords. The proposed rotary joint has very low rotational variation loss. The optical links are sufficiently stable to be applied to the antenna measurement. We verified that the rotary joint and optical links can be adopted in RF antenna test applications.