• Annals of Clinical Neurophysiology
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• v.5 no.1
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• pp.16-20
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• 2003

Background: Mobile phone has become a very popular device used in everyday our lives. However, the possible hazard to human body such as brain tumor has been proposed intermittently. This unwanted possibility was calmed down due to the absence of definite evidence of hazard. This study was performed to see the effect of mobile phone use on the brain temperature. Methods: In 20 volunteers, we performed 4 steps of temperature measuring procedure. Four steps are pre-use (S1, basal state), wire-phone (S2, conventional telephone), PCS phone (S3, using 1,750~1,900 MHz), cellular phone (S4, using 820 MHz) states. Brain temperatures were measured by radiothermometer at 10 sites (5 sites in each hemisphere) of the brain after 5minutes of telecommunication through the phones. The final data were compared using paired t-test. Results: In PCS phone user group (Average; $35.73708^{\circ}C$), brain temperature decreased (with statistical significance, p<0.05), compared to those of non-user group (Average; $35.9527^{\circ}C$) or conventional wire phone user group. In cellular phone user group (Average; $35.82155^{\circ}C$), brain temperature decreased slightly (without statistical significance, p>0.05) compared to those of non-user group (Average; $35.9527^{\circ}C$) or conventional wire phone user group (Average; $35.922^{\circ}C$). The temperature change was not limited to the mobile phone applied side but on both hemisphere of the brain. Conclusion: In conclusion, mobile phone (especially PCS phone) decreased brain temperature in both hemispheres without side-to-side temperature difference. In addition, this study suggests possibility of radiothermometer application to the study of electromagnetic wave effect and protection method research in the future.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.149-155
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• 2014

In this paper, we study the complex mobile antenna for WPT(Wireless Power Transfer) with NFC(Near Field Communication) of inductive coupling using FPCB which has half thickness compared with the existing coil type antennas. Considering the pattern thickness of loop antenna, the analysis of electromagnetic wave absorber and battery's influence, absorber thickness, the ranges of design parameters are obtained. The proposed antenna has 0.45 mm thickness using single layer 3 oz FPCB and absorber. From measurement, the characteristics of NFC antenna can be satisfied with the specifications of EMVCo. and domestic mobile telecommunication and the transmission efficiency of the proposed WPT antenna is 68.1 % which is competitive with the existing coil type antenna. From the results of this paper, it has been confirmed that the proposed antenna can be used as the WPT and NFC antenna for mobile phone. Key words: Wireless Power Transfer, Near Field Communication, Mobile Phone Antenna, Absorber, FPCB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.155-161
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• 2018

Many short range weather radars with the low elevation search capability are needed for analysis and prediction of unusual weather changes or rainfall phenomena which occurs regionally. However, due to the characteristics of low elevation electromagnetic wave beam, it is highly probable that the received weather signals of these radars are contaminated by the ground and sea clutter. Since most of ground clutter appears around the very narrow low Doppler frequency region, it is somewhat easy to separate. However, the sea clutter removal is very difficult since it can occupy the broad Doppler frequency region according to weather conditions. Therefore, in this paper, the sea clutter removal capability is analyzed for a phased array weather radar which use vertical array elements for electronic elevation beam steering. Also, it is shown that the sea clutter removal can be achieved appropriately using the receiver beam forming technology in a phased array antenna.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.8
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• pp.1090-1098
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• 2018

Many short range weather radars with the low elevation search capability are needed for analysis and prediction of unusual weather changes or rainfall phenomena which occurs regionally. However, due to the characteristics of low elevation electromagnetic wave beam, it is highly probable that the received weather signals of these radars are seriously contaminated by the ground clutter. Therefore, the filter removing low Doppler frequency band is generally used to mitigate this problem. However, the phase noise in a radar system may limit the removal of the strong clutter and this may cause serious problems in estimating weather parameters because of the remaining clutter. Therefore, in this paper, the characteristics of phase noise in a radar system are investigated and the effects of the system phase noise are analyzed in the improvement of signal to clutter ratio for the strong clutter environment such as a short and low-elevated weather radar.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.469-472
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• 2008

In this paper, we discuss the recent trends on the passive UHF RFID tag chip design techniques and several important system parameters. We also summarize link budget studies on both conventional and modem UHF RFID communications. The paper highlights the reverse link limited case, which has known to be the minor concern if reader continuous wave (CW) can reach the tag in sufficient level. This makes sense when the tag sensitivity is rather high (over 10-12${\mu}W$); however, since the tag chip fabrication technologies have been developed by time, the tag chip threshold levels are now less-dominant in determining link margin. If the tag limitation can be alleviated, the forward link limited case can be resolved; thus, we rather focus on the path-loss problem. Since the path-losses are still exist in both forward and reverse links, and it can be doubled while CW travels the reader-tag-reader path because forward link and reverse link are on the same distance. Consider if reader receiver sensitivity is very high in the worst case. In this case, weaken tag response (i.e., backscatters) cannot reach the level that reader receiver can process tag data; bit-error rate can be higher. Overall, backscatter levels should be high enough so that reader receiver can correctly function. After discussing link budget, we carried out practical measurements on fading effects between two circularly polarized UHF RFID antennas in a small scale area.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.80-80
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• 2000

Surface acoustic wave (SAW) devices have become more important as mobile telecommunication systems need h호-frrequency, low-loss, and down-sized components. Higher-frequency SAW divices can be more sasily realized by developing new h호-SAW-velocity materials. The ZnO/diamond/Si multilasyer structure is one of the most promising material components for GHz-band SAW filters because of its SAW velocity above 10,000 m/sec. Silicon carbide is also a potential candidate material for high frequency, high power and radiation resistive electronic devices due to its superior mechanical, thermal and electronic properties. However, high price of commercialized 6- or 4H-SiC single crystalline wafer is an obstacle to apply SiC to high frequency SAW devices. In this study, single crystalline 3C-SiC thin films were grown on Si (100) by MOCVD using bis-trimethylsilymethane (BTMSM, C7H20Si7) organosilicon precursor. The 3C-SiC film properties were investigated using SEM, TEM, and high resolution XRD. The FWHM of 3C-SiC (200) peak was obtained 0.37 degree. To investigate the SAW propagation characteristics of the 3C-SiC films, SAW filters were fabricated using interdigital transducer electrodes on the top of ZnO/3C-SiC/Si(100), which were used to excite surface acoustic waves. SAW velocities were calculated from the frequency-response measurements of SAW filters. A generalized SAW mode. The hard 3C-SiC thin films stiffened Si substrate so that the velocities of fundamental and the 1st mode increased up to 5,100 m/s and 9,140 m/s, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.436-444
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• 2002

This paper presents a new method, which uses defected ground structure (DGS) on the ground planes of planar transmission lines such as microstrip and coplanar waveguide (CPW), to reduce the size of amplifiers. The main idea can be summarized as follow; DGS on the ground plane of microstrip or CPW line shows an increased slow-wave effect due to the additional equivalent L-C components. So the electrical length of the transmission line with DGS is longer than that of the standard transmission line for the same physical length. Then, the length of the transmission line with DGS can be shortened in order to maintain the original electrical length to be the same. This leads the matching of the original amplifier to be kept. In order to show the proposed method is valid, two kinds of amplifiers, the original amplifier and reduced amplifier, are fabricated, measured, and compared using both microstrip and CPW. The measured performances of the reduced amplifiers with DGS are quite similar to the ones of the original amplifiers for both microstrip and CPW amplifiers, even though the size of matching networks of the amplifiers with DGS are much smaller than those of the original amplifiers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.748-755
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• 2004

In this paper, the hybrid SC/MRC technique was applied to the MC/DS-CDMA system in the Nakagami-m multi-path fading environment. The applied scheme was compared with other cases when the MRC technique was applied and then performances were analyzed. The result of analysis showed that the performance of the applied system, whose number of branches (L) for the input diversity of each carrier wave was 3 and かme selected number of branches ( Lc) was 2, was better than that of the MRC technique when the Lc of the MRC technique was 2. The performance of the applied system was lower than that of the MRC technique, then the Lc of the MRC technique was 3. However, as the fading index was lowered, which means the telecommunication environment deteriorated, the performance of the hybrid SC/MRC-(2/3) diversity technique when Lc of MRC technique was 3, was almost the same as that of the MRC technique. The hybrid SC/MRC-(2/3) diversity technique shows a similar performance to that of the MRC technique, when the Lc of the MRC technique was 4. Therefore, it was confirmed that the MC/DS-CDMA system could reduce complexity and achieve similar performance to that of the MRC by applying the hybrid SC/MRC technique, which utilized the advantages of the SC technique and high performance of the MRC scheme, rather than the MRC diversity technique that requires bit synchronization, frequency of fading, and phase synchronization for every diversity branch.

• Progress in Medical Physics
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• v.10 no.1
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• pp.33-40
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• 1999

Purpose: To simulate and measure the signal intensity of various tissues near bone interface in 2D and 3D neurological MR images. Materials and Methods: In neurological proton density (PD) weighted images, every component in the head including cerebrospinal fluid (CSF), muscle and scalp, with the exception of bone, are visualised. It is possible to acquire images in 2D or 3D. A 2D fast spin-echo (FSE) sequence is chosen for the 2D acquisition and a 3D gradient-echo (GE) sequence is chosen for the 3D acquisition. To find out the signal intensities of CSF, muscle and fat (or scalp) for the 2D spin-echo(SE) and 3D gradient-echo (GE) imaging sequences, the theoretical signal intensities for 2D SE and 3D GE were calculated. For the 2D fast spin-echo (FSE) sequence, to produce the PD weighted image, long TR (4000 ms) and short TE$_{eff}$ (22 ms) were employed. For the 3D GE sequence, low flip angle (8$^{\circ}$) with short TR (35 ms) and short TE (3 ms) was used to produce the PD weighted contrast. Results: The 2D FSE sequence has CSF, muscle and scalp with superior image contrast and SNR of 39 - 57 while the 3D GE sequence has CSF, muscle and scalp with broadly similar image contrast and SNR of 26 - 33. SNR in the FSE image were better than those in the GE image and the skull edges appeared very clearly in the FSE image due to the edge enhancement effect in the FSE sequence. Furthermore, the contrast between CSF, muscle and scalp in the 2D FSE image was significantly better than in the 3D GE image, due to the strong signal intensities (or SNR) from CSF, muscle and scalp and enhanced edges of CSF. Conclusion: The signal intensity of various tissues near bone interface in neurological MR images has been simulated and measured. Both the simulation and imaging of the 2D SE and 3D GE sequences have CSF, fat and muscle with broadly similar image intensity and SNR's and have succeeded in getting all tissues about the same signal. However, in the 2D FSE sequence, image contrast between CSF, muscle and scalp was good and SNR was relatively high, imaging time was relatively short.