• 한국전자파학회논문지
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• 제14권2호
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• pp.192-201
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• 2003

본 논문은 일반적인 평면형 마이크로스트립 패치 안테나의 크기를 줄이고자 1.575 GHz 대역에서 패치면을 입체적 구조인 단방향 선형 주름형, 사각 주름형 및 격자 요철형으로 제안, 설계하였다. 설계 결과, 단방향 선형 주름형은 평면형 구조에 비해 패치의 공진길이가 21.4 % 단축되었으며, -10 dB 반사손실 대역폭은 62 MHz로서 평면형의 39 MHz(2.5 %)에 비해 23 MHz(1.5 %) 증가하였다. 이득은 평면형의 6.7 dBd에 비해 0.9 dB 저하된 5.8 dBd를 나타내었다. 3 dB 빔폭은 공진길이 단축으로 인해 E-면에서만 18$^{\circ}$ 증가하였다. 사각 주름형의 경우, 패치의 가시적 크기는 평면형에 비해 21.6 %의 면적 축소효과를 얻었다. 격자 요철형의 경우, 먼저 선형편파에 대해 패치 면적은 평면형에 비해 43.3 %의 면적 축소효과를 얻었다. -10 dB 대역폭은 70 MHz (4.4 %)로 평면형에 비해 31 MHz(2%)증가하였다. 이득은 2.2 dBd로서 평면형에 비해 4.5 dB 저하되었고, -3 dB 빔폭은 E-면에서 22$^{\circ}$, H-면에서 13$^{\circ}$ 각각 증가하였다. 원형편파의 경우, 패치의 크기는 평면형에 비해 41 %가 축소되었고, 축비는 0.8 dB의 양호한 원편파 특성을 얻었으며, 2 dB 이내 축비 대역폭은 20 MHz(1.27 %)로 평면형의 10 MHz(0.63 %)에 비해 증가되었다. 이로써 본 논문에 제안된 안테나 구조가 소형화면에서 크게 효과가 있고, 대역폭 증가로 인해 다양한 서비스가 부가된 시스템에서의 활용 가능성이 확인되었다.

• 한국지구과학회지
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• 제22권5호
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• pp.388-404
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• 2001

하부 성층권 온도의 추세에 대한 위성관측과 모델 결과들의 상대적인 정확성을 평가하기 위하여 두 종류의 위성관측 MSU 채널 4(57.95GHz) 밝기온도 자료들과 1981${\sim}$1993년 기간의 두 종류의 대순환 모델(ECMWF and GEOS) 재분석 자료들을 시계열 회귀분석으로 상호 비교하였다. 1980${\sim}$1999년 기간의 위성자료는 이 연구에서 유도된 직하점 MSU4와 여러 주사각에서 유도된 SC4(Spencer and Christy, 1993)이다. 위 기간에 전지구에 대한 MSU 하부 성층권 온도는 화산폭발과 관련된 냉각화 경향(-0.35K/decade)을 보였으며, 이러한 경향은 육지보다 해양에서 1.2배 컸다. 자료들의 공통 기간(1981${\sim}$1993년)에 대한 하부 성층권 온도의 아노말리는 두 종류 관측자료와 GEOS에서 전지구적으로 냉각화 경향(-0.14${\sim}$-0.42K/decade)을 보였으나, ECMWF는 북반구를 제외하고 온난화(0.06K/decade)를 보였다. 온도 연주기는 SC4를 제외하고 다른 세 종류 자료에서 유사한 위상과 함께 현저하였다. 온도 추세에 대한 95%신뢰도 조사에서 MSU 채널 4의 하부 성층권 온도에 대한 신뢰도가 채널 2(53.74GHz)의 중간 대류권 온도보다 더 낮았다. 또한 두 기층 사이의 온도 추세 감율이 북반구 육지에서 가장 컸다. MSU4에 대한 SC4 및 모델 재분석 결과들의 상관은 전지구의 경우에 SC4(r=0.96)에서 가장 높았고, ECMWF(r=0.61)에서 가장 낮았다. 한반도의 경우에는 GEOS에서 가장 높았고(r=0.88), ECMWF에서 가장 낮았다(r=0.73). MSU4에 대한 SC4, ECMWF의 상관은 아열대 제트류가 위치하는 $30^{\circ}$ 위도대에서 낮았으나(r<0.6) 그 외의 지역에서는 대체로 높았다(r>0.6). 한반도 부근에서 하부 성층권 온도의 냉각화 경향은 모든 자료에서 공통적으로 나타났다. 이러한 추세는 SC4(-0.82K/decade)에서 가장 컸으며, MSU4(-0.38K/decade), GEOS(-0.28K/decade), ECMWF(-0.07K/decade) 순으로 나타났다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.20-23
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• 2004

Tropospheric and ionospheric scintillation may impact on C-band satellite communication systems, particularly at lowmargin systems and low elevation angles. This paper presents the characteristics of C-Band scintillation at low elevation angle received and recorded the satellite signal from INTELSAT above the Pacific Ocean Region (POR) from January 2002 to December 2002 in the period of solar maximum. We received 3.9525 GHz beacon signal at Sri-Racha satellite earth station by the 32 meters in diameter antenna with 8 degrees of elevation. The analysis was found that the values of amplitude fluctuation is mostly about 0.5-0.6 dB peak to peak and $S_4$ = 0.03-0.04. The maximum amplitude fluctuation is about 9 dB peak to peak occurring in April. The occurrence numbers of scintillation is most frequently in April and minimum in November. The occurrence numbers of tropospheric scintillation are most frequently in April and October, and minimum in November. It relates to temperature and water vapor pressure variation in $N_{wet} $. The occurrence numbers of ionospheric scintillation are most frequently in April and September, and minimum in November. It varies corresponding to both equinoctial periods (vernal and autumnal equinox in March and September) and solstice periods (June and December) respectively.

• Progress in Superconductivity
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• 제11권2호
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• pp.106-111
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• 2010

Sapphire resonators with $YBa_2Cu_3O_{7-\delta}$ (YBCO) endplates have provided a way to realize extremely high quality factor due to the extremely low dielectric loss of sapphire and conductive loss of YBCO films, which enables to measure the low surface resistance of superconductor films at microwave frequencies. We present microwave properties of HTS sapphire resonators designed for measuring the surface resistance of HTS films at millimeter-wave frequencies by using the two-resonance mode dielectric resonator method. Despite enhanced surface resistance ($R_S$) of YBCO films due to the quadratic frequency dependence of the $R_S$, the unloaded quality factor ($Q_0$) of the $TE_{021}$ mode sapphire resonator still appears to be well above $1\;{\times}\;10^6$ at a mm-wave frequency of 38 GHz at 10 K. However, it appears that the $TE_{012}$ mode $Q_0$ is unexpectedly low despite that the corresponding resonance peak looks uncoupled with parasitic modes. We discuss possible reasons for the unexpected results using the surface resistance at the $TE_{021}$, $TE_{012}$, and $TE_{011}$ mode frequencies.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.190-196
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• 2001

The microwave dielectric properties and a sintering behavior of MgTiO$_3$-CaTiO$_3$ ceramics doped with Li were investigated. The main composition was fixed as 0.94MMgTiO$_3$-0.06CaTiO$_3$ and Li$_2$CO$_3$was added excessively in the range of 0~10 mol% (with reference to Li atoms) and the specimens were sintered at 1200~140$0^{\circ}C$ for 4 hours. When the amount of Li was small the quality factor and dielectric constant were reduced, while those tow properties increased if the Li amount was above 1 mol%. But if Li was overly added those dielectric properties decreased again. Li, if added in the composition range of 1.0~3.0 mol%, can increase the quality factor of MgTiO$_3$-CaTiO$_3$ ceramics. The optimum amount of Li was 1.5mol% and sinterign condition was 1275$^{\circ}C$/4hr, at which we cudl obtain following results ; dielectric constant ($\varepsilon$$_{r}$) of f20.0, quality factor(Qxf$_{0}$) of 78,000 GHz and temperature coefficient of resonant frequency($\tau$$_{f}$) of -1.6 ppm/$^{\circ}C$.>.>.>.

• 한국세라믹학회지
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• 제52권3호
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• pp.215-220
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• 2015

Phase evolution, microstructure, and microwave dielectric properties of $Li_2O$ and $Al_2O_3$ doped $Zn_{1.9}Si_{1.05}O_4$, i.e., $Zn_{1.9-2x}Li_xAl_x-Si_{1.05}O_4$, ceramics (x = 0.02 ~ 0.10) were investigated. The ceramics were densified by $SiO_2$-rich liquid phase composed of the Li-Al-Si-O system, indicating that doped Li and Al contributed to the formation of the liquid. As the secondary phase, ${\beta}$-spodumene solid solution with the composition of $LiAlSi_3O_8$ was precipitated from the liquid during the cooling process. The dense ceramics were obtained for the specimens of $$x{\geq_-}0.06$$ showing the rapid densification above $1000^{\circ}C$, implying that a certain amount of liquid is necessary to densify. The specimen of x = 0.06 sintered at $1050^{\circ}C$ exhibited good microwave dielectric properties; the dielectric constant and the quality factor ($Q{\times}f_0$) were 6.4 and 11,213 GHz, respectively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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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.

• 한국항해항만학회지
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• 제46권3호
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• pp.179-190
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• 2022

본 연구에서는 실리콘 기판 상에 제작된 3D 결합구조를 가지는 코프레너 선로인 CWP3DCS(coplanar waveguide employing periodic 3D coupling structures) 구조에 대한 특성임피던스와 대역폭특성을 연구하였으며 이를 통해 완전집적형 해양무선통신 반도체 SoC(System on Chip)를 구현하기 위한 수동소자의 개발가능성을 검토하였다. CWP3DCS에 대한 특성임피던스와 대역폭특성을 추출하기 위해서 삽입손실에 대한 측정값을 반영한 measurement-based equation을 유도하였으며, 이 방법의 유효성을 검증하기 위해 전송상수 β와 특성임피던스에 대한 측정값과 measurement-based equation으로부터 추출된 계산값을 비교하였다. 비교 결과에 의하면 특성임피던스와 전송상수 β에 대한 계산값과 측정값의 최대오차는 각각 3.9%와 6.4%의 값을 보여주었다. 본 논문의 연구결과에 의하면, CWP3DCS 구조는 주기적 구조의 길이 LT = 30 ~ 150 ㎛의 범위에서 통과대역이 121 GHz인 광대역 특성을 보여주었으며, 특성임피던스 역시 주파수 의존성이 매우 적은 광대역 특성을 보여주었다. 그리고, 20 ㎛의 선로 폭으로도 20 Ω이하의 낮은 임피던스를 가지는 전송선로의 구현이 가능하였으며, 동일한 임피던스를 가지는 기존 전송선로의 선로 폭 3mm에 비해 선로 폭이 크게 감소하였다. 그리고, 주기적 구조의 길이 LT값을 조정함으로써 원하는 특성임피던스 값을 가지는 구조를 반도체 기판 상에 용이하게 구현할 수 있음을 알 수 있었다. 상기 결과로부터 CWP3DCS 구조는 완전집적형 무선통신 반도체 SoC용 정합 및 수동소자로써 유용하게 사용될 수 있음을 알 수 있었다. 본 논문은 3D 결합구조를 가지는 코프레너 선로인 CWP3DCS의 대역폭에 대한 최초의 연구이다.

• 한국수산과학회지
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• 제15권4호
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• pp.283-290
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• 1982

Sardine and mackerel so called dark muscled fish have been underutilized due to the disadvantages in bloody meat color, high content of fat, and postmortem instability of protein. Recent efforts were made to overcome these defects and develope new types of product such as texturized protein concentrates and dark muscle eliminated minced fish. Approach of this study is based on the rapid dehydration of foamed fish-starch paste by dielectric heating. In process comminuted sardine meat was washed more than three times by soaking and decanting in chilled water and finally centrifuged. The meat was ground in a stone mortar added Ivith adequate amounts of salt, foaming agent, and other ingredients for aid to elasticity and foam stability. The ground meat paste was extruded in finger shape and heated in a microwave oven to give foamed, expanded, and porous solid structure by dehydration. Dielectric onstant $(\varepsilon')$ and dielect.ic loss $(\varepsilon")$ values of sardine meat paste were influenced by wavelength and moisture level. Those values at 100 KHz and 15 MHz were ranged 2.25-9.86; 2.22-4,18 for E' and 0.24-19.24; 0.16-1.20 for E", respectively, at the moisture levels of $4.2-13.8\%$. For a formula for fish-starch paste preparation, addition of $20-30\%$ starch (potato starch) to the weight of fish meat, $2-4\%$ salt, and $5-10\%$ soybean protein was adequate to yield 4-5 folds of expansion in volume when heated. Addition of e99 yolk was of benefit to micronize foam size and better crispness. In order to provide better foaming and dehydration, addition of $0.2-0.5\%$sodium bicarbonate, foaming agent, was proper to result in foam size of 0.5-0.7 mm and foam density of $200-400\;/cm^2$ which gave a good crispness. Heating time was depended upon the moisture level of fish-starch paste. For a finger shaped paste (1.0cm. $D\times10cm.L$) heating for 150-200 sec. in a microwave oven (700W. 2.45GHz) was sufficient to generate foams, expand, and solidify the porous structure of fish-starch paste. When the moisture content was above $55\%$ browning and scorching was deepened due to over-expansion and over-heating whereas the crispness was hardened by insufficient expansion at lower moisture content. In quality evaluation of the product, chemical composition of $30\%$ starch and $3\%$ salt added product was moisture $8.8\%$, lipid $2.4\%$, carbohydrate $46.7\%$, protein $36.1\%$, and ash $6.0\%$. Eleven membered panel test evaluated that fish-starch paste was acceptable in color, crisp-ness, taste, except a trace of fishy odour which could be masked by the addition of spice extracts.