• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.9
• /
• pp.872-875
• /
• 2016

In this paper, the turnstile junction-based Ortho-Mode Transducer(OMT) is designed and manufactured. It is usually well-known that turnstile junctions have symmetry structure of waveguide so the higher order modes, which occurs inside the waveguide, can be cancelled. Because of these symmetrical properties, the turnstile junction-based OMTs have merits like high transmission and low return loss characteristic in broadband and two different modes propagate orthogonally in common port resulting in the fully realization of double polarization. The designed OMT has the application of Radar Seeker and operates in W-band(94 GHz), the millimeter wave frequency. The average of return loss value of manufactured OMT is lower than -20 dB and it has bandwidth characteristic of over 500 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.8
• /
• pp.740-747
• /
• 2015

Recently, mobile communication systems using the millimeter-wave frequency band have been proposed, and the importance of efficient compensation of the nonlinearity caused by 60 GHz high-power amplifiers(HPAs) is increasing. In this paper, we propose a predistorter structure based on multiple coefficient sets which are separately used to different ranges of input power values. These ranges correspond to varying levels of nonlinearity characteristics. The structure is applied to the 60 GHz HPA FMM5715X and the performance of correcting the nonlinearity of LTE signals is evaluated. Evaluation results using a hardware testbed demonstrate that the proposed predistorter structure achieves the maximum of 6 dB gain over the conventional method in terms of the adjacent channel leakage ratio(ACLR).

• Journal of Advanced Navigation Technology
• /
• v.14 no.1
• /
• pp.11-19
• /
• 2010

In this paper, H-plane filtering-horn antenna operating at millimeter frequency band is proposed with embedded filter and three-layered dielectric lens for frequency selection and maintenance of main beam direction, respectively. The waveguide-typed filter and H-plane sectoral horn antenna are replaced with considerably size-reduced PCB substrate-typed filtering antenna using via fences and several posts. The waveguide-typed filter and H-plane sectoral horn antenna were designed in air-filled waveguide and then combined into size-reduced PCB substrate. For the control of the thickness of dielectric lens, single and multi dielectric lens have been employed. As a result of antenna gain, 8 and 13.5 dBi have been obtained at 41.5 GHz, respectively, from the simulations of single and multi-lens antennas.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.1 no.1
• /
• pp.35-39
• /
• 2008

In this paper, we have developed a propagation loss prediction software with GUI (Graphic User Interface) functions, based on the geometrical ray optics model, which can predict radio parameters for the deployment of wireless indoor network. The program has two numerical modules consisted with electrical image and ray launching methods to implement UTD theory. The simulated results are compared with reported data measured in the foreign building environments for office and '一' type corridor, and measured and simulated results for the propagation loss agree with each other quite well. Simulation results for '一' type corridor and 'T' type corridor propagation environment are shown for reference.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38C no.11
• /
• pp.1074-1077
• /
• 2013

This paper analyzes the benefit of using directional antennas against eavesdropping attack in millimeter wave (mmWave)-based networks. All devices are equipped with a directional antenna or an omni-directional antenna in a single-hop communications. The probability of a device being detected by an eavesdropper is analyzed based on the exposure region of a device. The relative detection rate is introduced to represent the benefit of using directional antenna. Numerical results show that there exists an optimal number of devices that maximizes the detection probability and it varies according to the parameters such as antenna beamwidth. It shows that the use of directional antenna enables to protect the devices from the detection by an eavesdropper for almost the whole situation in mmWave band communication.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.11
• /
• pp.1117-1124
• /
• 2011

In this paper, we implemented a Ka-band frequency synthesizer for millimeter wave seeker. We improved frequency synthesizer performance of phase noise, resolution and spurious using the DDS driven hybrid method The proposed frequency synthesizer has the bandwidth of 1 GHz, frequency switching time of below 9 ${\mu}s$, suppressed spurious level of below -68.9 dBc. phase noise of -113.58 dBc/Hz at offset 100 kHz and flatness of ${\pm}$0.7 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.9
• /
• pp.756-759
• /
• 2017

In this paper, the radar cross section of a tank is analyzed at millimeter wave W-band. We calculate the radar cross section of the tank using the program based on PO and PTD and the computed results are compared with those of commercial simulator to check the accuracy of computations. The radar cross section is calculated in terms of the incident angle, polarization, and tank with or without cannon. The radar cross section can be reduced by changing the shape of the turret that can be applied to stealth tanks.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.7
• /
• pp.1755-1763
• /
• 1998

The rain attenuatio of a radio channel above 10 GHz can have impact on the availability of the radio channel. The severity of the rain impairments increases with frequency and varies with regional location. This paper presents an estimation method for rain attenuation for millimeter-wave propagation in domestic environments. the dropsize distribution is assumed to be exponential, and the measurement data in the various countries which are simlar to the domestic environments are compared with the theoretical one by varying the dropsize distribution. A rain-rate conversion model which can convert .tau.-minutes rain-rate data to 1-minute rain-rate data for domestic environments is also discussed. Using the converted domestic rain-rate data, probabilty distributions of rain attenuation are computed.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2012.11a
• /
• pp.715-717
• /
• 2012

최근 대용량 모바일 트래픽을 효율적으로 처리하고 다양한 5세대 지식 서비스를 제공할 수 있는 차세대 이동통신 기술개발을 목표로 중추 네트워크라는 개념이 고려되고 있다. 중추 네트워크에서는 시스템 용량을 기존 이동통신 시스템 대비 크게 증대시키기 위하여 밀리미터파 대역에서 넓은 대역폭을 사용하고 빔형성 기술을 통하여 무선자원을 재사용한다. 그러나 밀리미터파 대역은 직진성이 매우 강하기 때문에 비가시거리 통신영역에서 통신 품질이 급격히 저하되는 문제점이 발생하며, 이를 해결하기 위해 중추 네트워크에서는 적절한 위치에 중계기를 설치하여 비가시거리 통신영역을 최소화하는 것을 고려한다. 본 연구에서는 기지국 및 중계기 위치에 따른 중추 네트워크의 성능을 분석하기 위해 개발된 시스템 레벨 시뮬레이터를 소개한다. 본 시뮬레이터는 중추 네트워크의 통신영역과 채널용량을 분석 및 연구하는데 크게 기여할 수 있을 것으로 기대된다.

• Journal of Satellite, Information and Communications
• /
• v.11 no.3
• /
• pp.133-137
• /
• 2016

Millimeter wave wireless communication systems, especially those targeting indoor high rate data transfer, have a strong requirement for high quality wireless link. Unfortunately, in this frequency band, the electromagnetic wave has to sustain the high propagation loss caused by the smaller wavelengths. In this scenario, beamforming technique, which enhances the link quality by focusing the radiation power on a direction, becomes one of the most important techniques in millimeter wave band wireless communication. In recent year, there been conducted many research on beamforming to improve the performance of wireless system. In this paper, we evaluate the performance of a simplified codebook-based beamforming scheme which is based on multiple-procedure and three-state beam selection. The simplified scheme significantly reduces beamforming setup time, comparing to the exhaustive searching, two-level searching adopted in IEEE 802.15.3c standard, and also conventional multi-level scheme.