• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.12
• /
• pp.12-20
• /
• 1998

The non-uniform leaky wave structure of the slits in a parallel-plate waveguide is analyzed from the viewpoints of transmitting(receiving) leaky wave antenna and grating coupler. Period and slit width are simultaneously varied along the leaky wave structure to construct the leaky wave structure with a specific distribution of complex propagation constant. Some results for the equivalent magnetic current distributions over the slits and the radiation characteristics of the leaky wave structure with various source(equivalent magnetic current) distributions such as Gaussian, uniform, cosine, cosine-squared, and Taylor distributions are given and compared with each other.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.4
• /
• pp.489-499
• /
• 2011

RFID technologies, which allow collecting, storing, processing, and tracking information by wirelessly recognizing the inherent ID of object through an attached electronic tag, have a variety of application areas. This paper presents a novel carrier leakage suppression RF(CLS-RF) front-end for ultra-high-frequency RF identification reader. The proposed reader CLS-RF front-end structure generates the carrier leakage replica through the nonlinear path that contains limiter. The limiting function only preserves the frequency and phase information of the leakage signal and rejects the amplitude modulated tag signal in the envelope. The carrier leakage replica is then injected into the linear path that contains phase shifter. Therefore, the carrier leakage signal is effectively cancelled out, while not affecting the gain of the desired tag backscattering signal. We experimentally confirm that the prototype shows a significant improvement in the leakage to signal ratio by up to 36 dB in 910 MHz, which is consistent with our simulation results.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.8
• /
• pp.45-53
• /
• 1999

Electromagnetic scattering by finite number of conducting strips loaded on a grounded dielectric is considered for the TM polarization case from the viewpoints of transmitting(receiving) leaky wave antenna and grating coupler. An integro-differential equation whose unknowns are the induced currents over the strips is derived and solved by use of the method of moments. In order to construct the non-uniform leaky wave structures with specific source(current) distributions over the strips, distances between two adjacent strips and strip width are simultaneously varied along the structure. From some results for the current distributions over the strips and surface wave powers, it is observed that the maximum coupling efficiencies of the appropriately constructed non-uniform leaky wave structures from the viewpoints of both a receiving leaky wave antenna and a grating coupler amount upto 95%, which are about 15% improvements compared with those(80%) of the uniform structures.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.1
• /
• pp.62-67
• /
• 2001

Velocities of leaky surface acoustic waves (LSAW/sub s/) were measured by using a line-focus polyvinylidene fluoride (PVDF) transducer and compared with theoretically calculated ones. Isotropic materials of Cu, Al, fused quartz, and anisotropic one of Z-cut α-quartz crystal were used as specimens. The velocities were obtained by the separation time between wave components reflected directly from the surface of specimen and LSAW components according to the defocusing distance. The measured velocities well agree with the theoretical results within 1％ error, and it was shown that the leaky pseudo-surface acoustic wave (LPSAW) as well as the LSAW propagates with the typical 6-fold anisotropy on the (0,0,1) surface of α-quartz.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.24-24
• /
• 2022

토양 수분은 육상 생태계를 지배하는 핵심 변수로 널리 간주되어 왔다. 따라서 토양 수분을 모니터링하고 추정하는 것은 수문, 농업, 생화학적, 및 기후 역학을 평가하는 데 필수적이다. 그러나 최대 토양 접촉을 요구하는 기존의 토양 수분 모니터링 방법은, 토양 교란을 최소화하여 토양의 고유 특성을 보전하지 못하는 한계가 있다. 이 문제를 극복하기 위해 본 연구에서는 비접촉 초음파 시스템을 이용하여 토양 수분을 평가 방법을 개발하였다. 이 시스템은 공기-토양 조인트 절반 공간에서 누설 레일리파(Rayleigh wave)를 측정하도록 설계되었다. 토양 수분의 변화에 대한 누설 레일리파의 측정은 통제된 실험 설계에서 모래, 실트, 점토와 같은 세 가지 토양 유형에서 평가하였다. 본 연구 결과에서 세 가지 토양 사례 모두, 누설 레일리파의 에너지와 토양 수분 사이에 밀접한 관계가 있음을 보였다. 그러나 모래에서 얻은 동적 매개변수의 특성은 실트 및 점토의 특성과 다른 형태를 보였다. 이러한 결과는 미세한 토양 입자와 대조적으로 굵은 토양 입자는 증발 과정에서 감소된 토양 강도로 설명될 수 있다. 관측된 누설 레일리파에서 얻은 동적 매개변수를 기반으로 토양 수분을 평가하기 위해 랜덤 포레스트 모형을 이용하였다. 예측된 토양 수분의 정확도는 모든 데이터 및 토양 유형에 관계없이 높은 정확도를 보였다(R² ≥ 0.98, RMSE ≤ 0.0089 m³ m^-3). 즉, 본 연구에서는 레일리파가 토양 교란 없이 토양 수분 변화를 지속적으로 평가할 수 있는 큰 잠재력을 가지고 있음을 보여주었다.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.4
• /
• pp.25-33
• /
• 1999

Leaky wave radiation and surface wave launching problems in a dielectrically covered and periodically slitted parallel-plate waveguide(PPW) are considered for the TEM wave incidence case. Both the infinite and finite periodic geometries are analyzed by use of the method of moments. Some numerical results for the reflected and transmitted powers in the PPW, radiation efficiency into the free space, surface wave launching efficiency into the slab, antenna gain, and radiation patterns against dielectric thickness are presented to show the effect of the dielectric cover on the performances of the slitted leaky wave antenna. In addition, the method for improving surface wave launching efficiency using the proposed periodic geometry is described and maximum launching efficiency of 97.5% is obtained theoretically. So this structure is thought to be promising as an efficient feeder of dielectric grating antenna as well as image guide.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.9
• /
• pp.1108-1119
• /
• 2016

This paper presents the spectral analysis and radiation pattern of low-frequency electromagnetic(EM) leakage signals according to the fundamental operations of smartphones. The EM leakage signals generated by the activation of four I/O sensor modules such as a touch-screen, a camera, a microphone and a speaker are captured by the commercial near-field magnetic probe with 1cm spatial resolution. The analysis results show that the leakage of the EM wave occurs strongly around the activated I/O sensor modules, AP(Application Processor) and memory modules. Also, the distinguishable frequency characteristic is shown in each spectrum of EM leakage signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.11
• /
• pp.1069-1074
• /
• 2004

In this paper, we have designed artificial double negative(DNG) transmission line composed of series inter-digital capacitor and two shunt inductive short stubs. This artificial DNG transmission line has the property of double positive (DPS) transmission line over some frequency ranges due to RF nature. In detail, this transmission line simultaneously has the contrary properties of DNG and DPS transmission line depending on operation frequency. DPS/DNG transmission line at leaky region is utilized to design frequency scanning antenna with backfire-to-endfire. We have simulated and measured the dispersion and for-field radiation beam patterns of symmetrical leaky wave antenna. The results show rough agreement.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.1248-1250
• /
• 2001

전기철도에서의 급전시스템은 레일을 귀선으로 사용하는 단상급전시스템을 사용하고 있다. 이에 따라 레일로부터 대지로의 누설에 의해 상당한 누설전류가 대지로 흐르게 된다. 대지로 흐르는 이 누설전류는 전자유도에 의해 선로 주변에 설치된 통신 케이블 또는 장치에 영향을 주게 된다. 더욱이 전기차의 견인시스템은 견인전동기를 제어하는데 있어서 스위칭 소자의 개폐에 의한 고조파 전류를 발생하고 있어 대지누설전류에 고조파 전류가 포함되어 흐른다. 본 연구에서는 전기철도 급전시스템에서 통신유도원인 대지누설전류에 따른 고려되어야 할 급전시스템 설계 파라미터를 시뮬레이션을 통하여 검증하였으며, 이 결과가 향후 급전시스템 설계시 기본적인 지침이 되어야 할 것이다.

• Korean Journal of Optics and Photonics
• /
• v.18 no.3
• /
• pp.190-195
• /
• 2007

A novel optical coupling filter with finite-thickness metal-strip gratings printed on optical planar dielectric slabs is proposed, and Bragg conditions of the device are rigorously evaluated by using Modal Transmission-Line Theory (MTLT). The numerical results reveal that the guiding structures have filtering properties due to a leaky-wave stop-band while conventional DFB guiding structures consisted of dielectric gratings depend on a feedback-wave stop-band. Consequently, it shows that the optical coupling titter dependent on the leaky-wave filtering characteristics can be compounded of such optical devices as LD and optical fiber.