• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.07a
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• pp.424-431
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• 2002

마이크로파 주파수는 일반적으로 1㎓-30㎓ 정도로서 주파수가 매우 높기 때문에 도체뿐만 아니라 절연체와 공기 중에서도 전류가 흐르는 성질을 갖는다. 자유공간에서의 마이크로파를 전자파라고도 하며 그 속도는 빛의 속도와 동일하며 자유공간에서 1cm-30cm 파장 범위를 가지므로 센티파라고도 한다. 전자방사(electromagnetic radiation)은 공간을 통하여 시간에 따라 변하는 전자계(electric and magnetic field)에 의한 에너지의 전파(propagation)이며 파동이론과 (wave theory)와 미립자이론(corpuscular theory)에 의해 해석될 수 있다. 전자파 이론(electromagnetic wave theory)의 기초는 1864년 Maxwell이 전자기 현상에 관하여 지배방정식을 수립함으로써 정립되었으며 1888년 Hertz에 의해 마이크로파의 존재가 실험적으로 증명되었다. 이후 마이크로파 기술은 2 차 세계대전을 거치면서 크게 발전하였으며 초기의 레이더 및 통신 등과 같은 군용 기술에서 마이크로파 건조 및 센싱과 같은 산업응용 기술로 발전하게 되었다. 특히 마이크로파 센서기술 및 가열기술은 농업 및 식품분야에 응용되어 마이크로파 응용제품을 선보이게 되었다. (중략)

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.7
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• pp.31-38
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• 1992

In this paper, numerical analysis package using Time-Domain Finite Difference (TDFD) method is developed to solve the initial value problem of Maxwell's equation and applied to several microstrip structures. TDFD allows us to show graphically the evolution of the crosswalk between microstrip lines. Moreover, we can obtain transmission line parameters and scattering parameters through Fourier transform of TDFD results in easy and efficient ways. TDFD is successfully applied to :1) wide band electromagnetic wave propagation along the single microstrip line, 2) crosswalk analysis between two microstrip lines, and 3) three metal line side-coupled filter. Our results show much better agreement with other theoretical experimental results reported in the literature. Thus we expect that TDFD is very useful to designing MMIC(Monolithic Microwave Integrated Circuit).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.330-337
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• 1998

In this paper, we fabricated a pair of circulaly polarized conical horn antennas for evaluating the scattering characteristics of a hemispherical reflector and of propagation characteristics in in-building environments, which is required for constructing a new wireless in-building communication system of microwave band consisted of a hemispherical reflector installed on the ceiling. The measurements show the fairly good features such that cross-polarization discremination more than 27 dB and axial-ratio less than 1.25 dB.

• Journal of Aerospace System Engineering
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• v.4 no.3
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• pp.24-28
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• 2010

The purpose of this study is to define available microwave absorbing structure for aircraft from in the X-band(8.2~12.4GHz) frequencies. The electromagnetic wave absorption or shielding techniques is an important issue not only for military purpose but also for commercial purposes. Aircraft Radar Absorbing Structure(RAS) is absorbed or scattered propagation waves from the enemy radar. There are absorbing technologies at shaping design techniques and using Radar Absorbing Materials(RAM). RAM is more important because shaping design can't include perfect radar absorbing performance. In this study, based on material properties was introduced RAM and to analyze the each characteristics. Finally, we comparison appropriate RAM for aircraft.

• Coupled systems mechanics
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• v.10 no.2
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• pp.185-198
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• 2021

An analytical model is consider to scrutinize axisymmetric wave propagation in multiferroic hollow cylinder with rotating and initial stressed forces, where a piezomagnetic (PM) material layer is bonded to a piezoelectric (PE) cylinder together by Linear elastic materials with voids. Both distinct material combos are taken into account. Three displacement potential functions are introduced to uncouple the equations of motion, electric and magnetic induction. The numerical calculations are carried out for the non-dimensional frequency by fixing wave number and thickness. The arrived outputs are plotted as the dispersion curves for different layers. The results obtained in this paper can offer significance to the application of PE/PM composite hollow cylinder via LEMV and CFRP layers for the acoustic wave and microwave technologies.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.391-394
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• 1998

Telecommunication system demands for increased bandwidths and operating frequencies for analog signal processing could be satisfied in the near future by the emergence of a novel technology based on magnetostatic waves propagating in low loss ferrimagnetic films. The magnetostatic wave n the only available technology for analog signal processing directly at microwave frequencies.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.413-419
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• 1987

In this paper, self-oscillating mixer is designed by small signal S-parameter and series feedback circuit. The input-output matching circuit is accomplished from double stub and additional matching stub. The self-oscillating mixer is oscillating itself and amplifies without any external local oscillator and an intermediate frequency amplifier, so it has advantages in its economical and system simplification. The experimental results show the maximum conversion gain 1.5d B and the noise figure 6.5d B at RF center frequency 4GHz and IF 1.1GHz` output oscillating power 4d Bm, efficiency 13.4%, stability -10MHz/V and -0.5MHz/\ulcornerC at oscillating frequency 5.1GHz.The rejection band loss characteristics in band pass filter and low pass filter are -40d B and -30d B, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.45-51
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• 2009

The propagation characteristics in parallel plate waveguide with dielectric layer having periodic metal strip pattern are investigated. PIN diode ON/OFF states are regarded as the short and open circuit, respectively, in the simulation using CST's MWS. The $11.25^{\circ}$, $22.5^{\circ}$, and $45^{\circ}$ layers which can be used for X-band 4-bit Radant lens phase shifter, are designed. The simulated results for each dielectric layer are $11.28^{\circ}$, $23.2^{\circ}$, and $46.22^{\circ}$, respectively. Also, the equivalent circuit of each layer at the operating band is realized and simulated using Agilent's ADS. The ADS simulated results are compared with the MWS simulated ones. Measured differential phase shills at the center frequency are $9.6^{\circ}$, $22.4^{\circ}$, and $43^{\circ}$, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1223-1232
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• 2008

In this paper, an analytic method is proposed to extract the reference slot admittance required for the design of a non-resonant waveguide edge slot array. A slot and two neighboring transmission line sections of the numerous alternately inclined slots with the identical inclination angle are modelled as a uniform lossy transmission line, and thus, the total ABCD matrix is easily calculated and compared with the simulated or measured one. From this procedure, the complex characteristic impedance and the complex propagation constant of the lossy transmission line are calculated and the normalized slot admittance is analytically obtained. In order to validate the proposed method, the admittance value of a reference slotted waveguide fabricated for designing the X-band edge slot array is extracted and it is compared with the one obtained by the other conventional method.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.350-353
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• 2003

Millimeter-wave dielectric ceramics have been used like applications for ultrahigh speed wireless LAN because it reduces the resources of electromagnetic wave, and Intelligent Transport System (ITS) because of straight propagation wave. For millimeterwave, the dielectric ceramics with high quality factor (Q$.$f), low dielectric constant($\varepsilon$), and nearly zero temperature coefficient of resonant frequency ($\tau$) are needed. No microwave dielectric ceramics with these three properties exist except Ba(Mg$\_$1/3/Ta/sub1/3/)O$_3$ (BMT), which has a little high s: In this paper, alumina (Al$_2$O$_3$) and fosterite (Mg$_2$SiO$_4$), candidates for millimeter-wave applications, were studied with an objective to get high q$.$f and nearly zero $\tau$$\_$f/ For alumina ceramics, q$.$f more than 680,000 GHz was obtained but it was difficult to obtain nearly zero Qf. On the other hand, for forsterite ceramics, q$.$f was achieved from 10,000 GHz of commercial for sterite to 240,000 GHz of highly purified MgO and SiO$_2$ raw materials, and $\tau$$\_$f/ was reduced a few by adding TiO$_2$ with high positive $\tau$$\_$f/.