• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.5 s.96
• /
• pp.541-548
• /
• 2005

The research deals with the prediction and the measurement of electromagnetic wave propagation in rectangular shaped tunnels at f=2.65 GHz. The received power level was measured in the straight and the curved tunnel by using a spectrum analyzer and Satellite DMB mobile phone. Thus we have gotten the data for two cases, the straight and the curved tunnel whose radius is 300m. In addition, the prediction of wave propagation was conducted based on the ray-launching method, in same tunnel where measurement was performed. A good agreement of the measured and the predicted path loss could be confirmed. The measured path loss shows a marked difference in propagation loss: the path-loss exponent, 3.21, and 3.98, for a straight and a curved tunnel, respectively. The reason that path-loss exponent is high in a curved tunnel is that there is no direct wave but only the reflected waves, which attenuates rapidly with distance due to multiple reflections. Also the predicted path loss shows path loss exeponent, 3.2 and 3.95, for a straight and a curved tunnel which are similar to the simulation results.

• Journal of the Korea Society of Computer and Information
• /
• v.12 no.6
• /
• pp.131-137
• /
• 2007

I intend to seek the shortest path which an aircraft safely flies to its destination through the shadow volume of three dimensional terrain which propagation does not extend. Herein, I propose a method in which a relatively wide shadow volume is divided with a polygon type of block polygon, a path up to the intermediate destination is sought in the divided block polygons according to the weight, and then, the shortest path up to the final destination is sought by repeating courses for seeking a destination again from the adjacent polygon based on the starting point of the intermediate destination within the divided polygon. The shortest path was searched by using the revised algorithms which apply to a critical angle from graph growth algorithms on the shadow volume which propagation on the actual three dimensional terrain does not extend to. The experiment shows that a method proposed in this paper creates effective flying curves.

• Journal of Advanced Navigation Technology
• /
• v.28 no.2
• /
• pp.172-177
• /
• 2024

This paper presents a method to overcome the problem of increasing elevation estimation error when estimating elevation in a multipath situation with radar. A multipath situation means that radar reception signals reflected from the same target come from multiple paths. In non-multipath, the monopulse method is accurate. For the opposite case, the least square error method is accurate. In multipath situation and when the elevation angle is very low, a singular occurs where the least square error estimate diverges. This singular was identified based on the propagation factor, and monopulse and least square error estimation methods were selectively used. As a result, we succeeded in increasing the accuracy of elevation estimation. MATLAB simulations were performed to verify the method proposed in this paper.

• Proceedings of the Korean Information Science Society Conference
• /
• 2001.10c
• /
• pp.157-159
• /
• 2001

인터넷 화상전화는 저렴한 가격으로 통신이 가능하게 하는 기술로 최근에 주목을 받고 있다. 인터넷은 제한적인 대역폭과 가변적인 손실을 나타내므로, 인터넷을 통해 전송되는 화상은 오류 전파에 의해 품질이 크게 떨어지게 된다. 일반적으로 화상은 움직임 예측, 보상기법을 이용하여 압축되기 때문에 한 프레임에서 발생한 오류가 그 프레임을 참조하는 프레임으로 전파되는 데 이를 오류 전파라고 한다. 기존의 오류 전파를 방지하는 기법에는 Error Tracking, NEWPRED, PFEC등이 있다. 본 논문에서는 인터넷 화상 전화에서 화상의 움직임이 적은 특성을 고려하여 Motion Vector의 중복전송을 이용한 PRMS기법을 제안한다. PFEC에 비해 부호화 효율을 높이면서 MB단위로 참조 프레임을 선택하여 오류 전파를 효과적으로 방지하는 기법이다. 실험을 통하여 PRMS기법이 기존치 PFEC나 NEWPRED에 비해 성능이 우수함을 보인다.

• The Journal of Natural Sciences
• /
• v.8 no.2
• /
• pp.101-109
• /
• 1996

In this paper, using the derived formula based on field theory both geometrical optics and diffraction theory, several features of same buildings of Bertoni's construction that influence the propagation of signals between antennas located on the same floor have been investigated theoretically and compared with previously studied results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.10
• /
• pp.1017-1024
• /
• 2002

In this paper, we present the analysis of radio wave propagation characteristics in curved tunnels. Tunnel propagation models are performed in two cases which are using ray-tracing method for straight tunnels and geometrical optics extension to the standard hybrid waveguide model for curved ones. By regression analysis for measured power based on distance between the transmitter and the received antenna in tunnels that have 3.5 m $\times$ 6 m cross section and limited wall depth path loss are 0.19 dB/m for straight section and 0.68 dB/m for curved ones. By comparing model analysis with measurement in tunnels, it has been shown that the simulated results of tunnel propagation models are similar to the measured values.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.651-654
• /
• 2008

협대역 다중접속 방식의 한계를 벗어난 Ultra-wide band(UWB) 기술이 고속 데이터 전송을 위해 많이 개발되어지고 있다. UWB 시스템은 방사전력 제한을 두고 있어서 근거리 실내 무선통신 분야에서 활용 범위가 확대되고 있다. 하지만 실내 무선 환경에서는 벽, 천장, 바닥 그리고 실내에 위치한 장애물 등에 의한 다중경로 페이딩 영향으로 초고속 실내 무선통신 서비스를 제공하는데 어려움이 있다. 이러한 실내 다중경로 성분에 의한 페이딩을 경감시키는 여러 가지 방법 중에서 원형편파를 이용하면, 상대적으로 긴 지연을 갖는 강한 다중경로 성분을 효과적으로 제거할 수가 있기 때문에 수신신호의 RMS 지연 감소, 페이딩 경감 및 신호강도 개선효과 등을 얻을 수 있다. 본 논문에서는 원형편파를 고려한 수정된 UWB 채널의 파라미터를 수정 정립하였고, 수정된 채널모델을 UWB 시스템에 적용하여 성능 개선을 시도하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.7
• /
• pp.455-461
• /
• 2015

The paper deals with the accuracy comparison between two kinds of ultrasonic paths for flow rate measurement. In the Z-path, two transducers are installed on the opposite sides of each other on a pipe, and the ultrasonic waves generated at one transducer propagate to arrive at the other one only by refraction. In the V-path, two transducers are installed on one side of a pipe, and the ultrasonic waves reflected at the inner wall of the pipe are received. Transit times were confirmed to identify the propagation paths by comparing the theoretically calculated results and measured ones. The flow rate measurements with two kinds of ultrasonic paths appeared very similar. It would be possible to select either of the paths by considering the advantages and disadvantages.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.736-738
• /
• 2014

The paper deals with the accuracy comparison between two kinds of ultrasonic paths for flow rate measurement. In the Z-path, two transducers are installed on the opposite side of each other on a pipe, and the ultrasonic waves generated of one transducer propagate and arrive at the other one only through refraction. In the V-path, two transducers are installed on one side of a pipe, and the ultrasonic waves reflected at the inner wall of the pipe are received. The backgrounds were established to select one path to fit the usage by considering the advantages and disadvantages.

• Proceedings of the Korean Information Science Society Conference
• /
• 2004.10a
• /
• pp.691-693
• /
• 2004

0.18$\mu\textrm{m}$ 표준 셀 라이브러리로 구현할 때 2.69㎱의 임계 경로 지연을 가지는 SIMD구조의 포화 덧셈기를 설계하였다. 기존의 설계에서 임계 경로를 구성하는 CLA를, 8비트까지만 자리올림(Carry)이 전파될 때 정확한 계산을 보장하는 근사 덧셈기의 형태로 설계한 결과, 임계 경로 시간 지연을 약 22% 감소시킬 수 있었다. 파이프라인 구조 프로세서에서 사용될 포화 덧셈기의 근사계산이 실패하는 경우에는, 추가적인 2개의 클록주기 동안 재 계산을 수행하게 된다.