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National Radio Research Agency | Date: 2015-05-15

An apparatus for measuring an antenna radiation pattern comprises a lower bearing unit; a hollow mast which is installed in the vertical direction; a hollow vertical bar, the length of which is vertically adjustable in a state; a goniometer which is horizontally coupled to the upper part of the vertical bar; a horizontal shaft which is positioned at the upper part of the goniometer; a first mounting unit, the length of which is vertically adjustable in a state; a second mounting unit having a vertical shaft which is coupled to the horizontal shaft by vertically penetrating one end of the horizontal shaft, the second mounting unit being installed on the upper end of the vertical shaft; and a support unit of which one end is coupled to the horizontal shaft and the other end is coupled to the outer periphery of the mast.

News Article | October 28, 2016

The only iPhone 7 Series cell phone case on the market that is designed to protect users from excessive radiation is available now, as part of the RF Safe Cooperation’s new three component iPhone 7 Safety Package. The case is designed with a cell phone radiation shielded flip cover to protect the user from microwave exposure. RF Safe, global leader in EMF safety, has launched its next generation iPhone 7 safety package, also featuring the RF Safe AirTube Headset, and RF Safe Ferrite Bead, a simple clip on device to provide cell phone radiation shielding for wired headsets. “Radiation safety is often like safely operating a motor vehicle. You use a blinker, seat belt, and headlights to maintain a safe driving experience,” says RF Safe founder, John Coates, “With cell phone radiation, it’s critical to have user knowledge of the wireless device to maintain proper distances and correctly use RF shielding.“ Health experts have been issuing warnings to consumers about the damaging impact cell phone radiation could have. The American Academy of Pediatrics (AAP) recently reinforced recommendations to utilize hands-free kits and limit usage. According to a recent report by ZDNet, an assemblyman of the National Radio Research Agency of South Korea claims that the new iPhone 7 and iPhone 7 Plus have twice the average special absorption rate (SAR) value in comparison to Samsung phones. Bluetooth technology powers the new iPhone 7 AirPods. Dr. Joel Moskowitz, a professor at the UC Berkeley School of Public Health, recently warned consumers that over time these emissions wear down the blood-brain barrier, which is essential for keeping out chemical toxins. With the AirPod, most of the wireless communications will emanate from the ear canal itself, according to details outlined by Apple last week. Apple’s W1 wireless chip, a focal point of the updated wireless technology, is housed in the bulbous portion of the AirPod that nestles into the ear canal. “You are putting a microwave-emitting device next to your brain,” says Moskowitz. With the AirPod sending high-tech radiation right into your ear, RF Safe says it could pose serious, long-term dangers, particularly for children. The RF Safe AirTube Headset features air tube acoustic technology, reducing microwave exposure to the head. iPhone users will experience the newest innovation in radiation safe cell phone headsets, and rich live sound without any electrical components in their ears. $1 from all pink RF Safe products will be donated help fund breast cancer research for National Breast Cancer Awareness Month. Since 1998 RF (Radio Frequency) Safe has been dedicated to evolving the wireless industries safety standards, by engaging in the business of design, testing, manufacture, and sale of safety technologies to mitigate harmful effects of cell phone radiation.

Choi D.-G.,National Radio Research Agency | Kim K.-H.,National Radio Research Agency | Choi J.,Hanyang University
IEICE Transactions on Communications | Year: 2015

New Target Specific Absorption Rate (SAR) Values, Calculated Using A Proposed Reference Dipole Antenna And The Reference Flat Phantom, Are Presented For An SAR Validation Test At 150 MHz. The Reference Flat Phantom Recommended By The International Electrotechnical Commission (IEC) Standard For 150 MHz Requires A Significant Amount Of Liquid Owing To Its Large Size. We Conduct A Numerical Analysis In Order To Reduce The Size Of The Flat Phantom. The Optimum Size Of The Flat Phantom Is 780 (L1) X 540 (W) X 200 (H) Mm3, Which Is Approximately A 64% Reduction In Volume Compared To The Reference Flat Phantom. The Length Of The Reference Dipole Antenna Required For The Optimized Flat Phantom (extrapolated From The Reference Values At 300 MHz) Becomes 760 Mm. The Calculated And Measured Return Losses (S11 ) Of The Antenna At 150 MHz Are 24.1 DB And 22 DB, Respectively. The Calculated And Measured Results For The Return Loss Of The Dipole Antenna Agree Well And Satisfy The IEC Standard (> 20 DB). The Target SAR Values Derived From The Numerical Analysis Are 1.08 W/kg For 1 G Of Tissue And 0.77 W/kg For 10 G Of Tissue For An SAR Validation Test At 150 MHz. Copyright © 2015 The Institute Of Electronics, Information And Communication Engineers.

Choi D.G.,National Radio Research Agency | Kim K.H.,National Radio Research Agency | Jang J.D.,National Radio Research Agency | Chung S.Y.,National Radio Research Agency | Gimm Y.M.,Dankook University
IEEE International Symposium on Electromagnetic Compatibility | Year: 2014

SAR measurement requirement which had been applied only to mobile phones was expanded to other portable wireless communication equipments used within 20 cm from the human body according to Korea radio regulation in Jan. 2012. The two-way radio operating at 150 MHz was newly included in revised radio regulation of SAR assessment. Although international SAR measurement standard IEC 62209-2 requires SAR evaluation to be above 30 MHz, most of the technical specification for SAR validation are not described below 300 MHz. The physical dimensions of the flat phantom, reference dipole antenna, and the target SAR values are suggested to use them as reference values for SAR validation at 150 MHz. The suggested dipole antenna and flat phantom structures were made and tested to prove their validities. © 2014 The Institute of Electronics, Information and Communication Engineer.

Kim K.J.,Yonsei University | Choi W.C.,Yonsei University | Yoon Y.J.,Yonsei University | Bae S.-H.,National Radio Research Agency
2015 International Workshop on Antenna Technology, iWAT 2015 | Year: 2015

The 8×8 array applicator for 915 MHz hyperthermia proposed. Proposed array applicator is 8×8 lattice array with and without phased feeding. 8×8 lattice array with same phase is for superficial hyperthermia. 8×8 lattice array with phased feeding is for ultra-superficial hyperthermia, which has deeper treatment area. 8×8 lattice array without phased feeding has 61 % effective treatment area of array size in 2 cm depth from skin surface. 8×8 lattice array with phased feeding has penetration enhancement from 34 mm to 49 mm. © 2015 IEEE.

Khuyen B.X.,Hanyang University | Tung B.S.,Hanyang University | Yoo Y.J.,Hanyang University | Kim Y.J.,Hanyang University | And 3 more authors.
Current Applied Physics | Year: 2016

An ultrathin and angularly stable metamaterial perfect absorber (MPA) is demonstrated for VHF-band using four connected split-square resonators structure and low-cost fabrication process. The total incoming energy of electromagnetic wave (at 250 MHz) is consumed inside the efficient thickness, which is 240 times smaller than the absorption wavelength of MPA. Our MPA works well for a very wide range of incident angle up to 45° of electromagnetic wave and exhibits the polarization-independent behavior. Furthermore, by scaling the initial design and integrating a ferroelectric material (strontium titanate), a thermo-tunable ultrathin MPA is realized in the THz region. At room temperature (300 K), the thickness of THz MPA reaches roundly 1/300 of the working wavelength. In addition, a fractional frequency shift of 49% at the absorption over 90% can be controlled in the varied temperature range from 150 to 400 K. Our results presents good candidates for potential devices operating from the radio to the THz range. © 2016 Elsevier B.V. All rights reserved.

Park J.,National Radio Research Agency | Kim W.N.,National Radio Research Agency | Kang B.-G.,National Radio Research Agency | Yeon H.,National Radio Research Agency
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

The existing calibration methods of EMI antenna have to use three antennas. Even standard antenna method replacing the standard antenna by the calibrated antenna needs a common transmitting antenna. In this paper, a simple calibration method which uses only two antennas is discussed. The method requires a information for electric fields at receiving location. Standard antennas knowing antenna factors can determine such electric fields. Calculable standard dipole antenna has theoretical antenna factors and site insertion losses calculated by Numerical Electromagnetic Code in free space or in open area test site with infinite perfect conducting plane. Formula of new calibration method using the standard antenna are derived. Antenna factors measured by new method in open area test site of National Radio Research Agency (NRRA) are compared to the theoretical values. The results show good agreements within 0.09 dB from 30 MHz to 1 GHz. © 2014 IEEE.

Bae S.-H.,National Radio Research Agency | Cha D.-H.,National Radio Research Agency
2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), USNC-URSI 2014 - Proceedings | Year: 2014

TVWS service is expected to be introduced in the near future. It should have to be capable of providing the broadcasting and TVWS services. However, it is difficult to share between broadcasting service and TVWS service in dense urban areas of the propagation environment. To date, there is no propagation prediction model for analysis of the two services. Recommendation ITU-R P.1546, propagation prediction method, is one of the candidates to analyze the both services. Recommendation ITU-R P.1546 is a point-to-area propagation prediction model, which is 30 ∼ 3000 MHz of the frequency band corresponding to the intervals 1 ∼ 1000 km distance. But it lacks accuracy for urban propagation model less than 1 km. © 2014 IEEE.

Khuyen B.X.,Hanyang University | Tung B.S.,Hanyang University | Dung N.V.,Hanyang University | Yoo Y.J.,Hanyang University | And 5 more authors.
Journal of Applied Physics | Year: 2015

We numerically and experimentally demonstrated a metamaterial perfect absorber (MPA) in MHz region based on a planar sandwiched metal-dielectric-metal structure. First, the single-peak perfect absorption was obtained at 400MHz. The ratios of the periodicity of unit cells and the thickness to the absorption wavelength are 1/12 and 1/94, respectively. The advantage of structural design and the mechanism for the low-frequency MPA are described in detail by the comparison between calculation, simulation, and experiment. Influence of the incident angle of electromagnetic (EM) wave for both transverse-electric (TE) and transverse-magnetic (TM) polarization on absorption was also investigated, and the absorption was maintained to be above 95% at incident angles up to 30°. Finally, we propose a self-asymmetric structure, which induces the dual-band perfect absorption in the same range of frequency. The EM behavior of the excitation modes and the mechanism of the dual-band MPA are clearly explained. Especially, when two resonance modes are finely controlled to be close enough, the bandwidth (full width at half maximum) of MPA is enhanced to be nearly wider twice than that in case of single-peak perfect absorption. The enhanced bandwidth is still well preserved by varying the incident angle up to 30°for both TE and TM polarization. The results were also confirmed by both simulation and experiment. Our work is promising for potential practical applications in the radio range, such as radio-frequency shielding devices, single/dual-frequency filters, and switching devices. © 2015 AIP Publishing LLC.

Park J.,Korea Astronomy and Space Science Institute | Kwak Y.-S.,Korea Astronomy and Space Science Institute | Mun J.-C.,National Radio Research Agency | Min K.W.,Korea Advanced Institute of Science and Technology
Journal of Astronomy and Space Science | Year: 2015

In this study, we estimated the topside scale height of plasma density (Hm) using the Swarm constellation and ionosondes in Korea. The Hm above Korean Peninsula is generally around 50 km. Statistical distributions of the topside scale height exhibited a complex dependence upon local time and season. The results were in general agreement with those of Tulasi Ram et al. (2009), who used the same method to calculate the topside scale height in a mid-latitude region. On the contrary, our results did not fully coincide with those obtained by Liu et al. (2007), who used electron density profiles from Arecibo Incoherent Scatter Radar (ISR) between 1966 and 2002. The disagreement may result from the limitations in our approximation method and data coverage used for estimations, as well as the inherent dependence of Hm on Geographic LONgitude (GLON). © 2015. The Korean Space Science Society.

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