• 전자통신동향분석
• /
• 제32권5호
• /
• pp.85-96
• /
• 2017

The research, design, and development of wireless access technologies using the new 6 to 100GHz band mmWave are actively underway in order to address the frequency shortage problem in the sub-6GHz band and accommodate the 5G technical requirements, such as the increased transmission capacity. Technical elements to efficiently overcome the problems caused by mmWave signal characteristics, support an effective interworking with a conventional communication service, and ensure smooth mobility between mmWave base stations and existing base stations are also being investigated. This paper discusses the technical solutions for an mmWave-based 5G RAN configuration and their considerations under various operational scenarios.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 ITC-CSCC -2
• /
• pp.1009-1012
• /
• 2000

In this paper, we have designed and fabricated power PHEMT’s with an unit gate width of 80$\mu\textrm{m}$ and 4 fingers, and MIMIC power amplifiers using the PHEMT’s as well. The PHEMT’s have a 0.2$\mu\textrm{m}$ gate length and source to drain spacing of 3$\mu\textrm{m}$. The characteristics of the fabricated PHEMT’s are 4.08dB of S$\sub$21/ gain at the 35GHz and 317mS/mm of gm, and 62GHz of f$\sub$T/ and 120GHz of f$\sub$max/. The designed and fabricated MIMIC’s power amplifiers with 6 PHEMT’s and MIN capacitors were fully passivated by 1000 Α of Si$_3$N$_4$ film for higher performance and surface protects. The chips were processed using the MINT processes, and size was 3.25 ${\times}$ 1.8$\textrm{mm}^2$. The fabricated MIMIC power amplifiers have RF characteristics such as 11.25dB of S$\sub$21/ gain, 11.37dB of input return-loss and 12.69dB of output return-loss at the 34.55GHz.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1998년도 추계종합학술대회 논문집
• /
• pp.633-636
• /
• 1998

In this study, power AlGaAs/InGaAs/GaAs PM-HEMT's for mm wave's were fabricated using Electron beam lithography and air-bridge techniques, and so on. DC and AC characteristics of the fabricated power PM-HEMTs were measured under the various bias conditions. For example, DC and RF characteristics such as S21 gain of 3.6 dB at 35 ㎓, current gain cut-off frequencies of 45 ㎓ and maximum oscillation frequencies of 100 ㎓ were carefully analyzed for design methodology of sub-mm wave power devices.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제18권7호
• /
• pp.2010-2026
• /
• 2024

This work investigates the hybrid precoder scheme in a millimeter wave (mmWave) multi-user MIMO system. We study a sum rate maximization scheme by jointly designing the digital precoder and the analog precoder. To handle the non-convex problem, a block coordinate descent (BCD) method is formulated, where the digital precoder is solved by a bisection search and the analog precoder is addressed by the penalty dual decomposition (PDD) alternately. Then, we extend the proposed algorithm to the sub-connected schemes. Besides, the proposed algorithm enjoys lower computational complexity when compared with other benchmarks. Simulation results verify the performance of the proposed scheme and provide some meaningful insight.

• 항공우주시스템공학회지
• /
• 제17권1호
• /
• pp.42-50
• /
• 2023

본 연구에서는 SrZn_2-xCo_xFe₁₆O₂₇ 화학식을 갖는 육방정 구조의 페라이트 분말을 고상법으로 합성하고 Co-Zn 함량 변화에 따른 전자기파 흡수 특성을 0.1-18 GHz의 주파수 범위와 0 ~ 10 mm 흡수체 두께 범위에서 평가하였다. 흡수체 두께에 따른 전자기파 흡수 특성은 고주파 복소 투자율과 유전율 측정 data로부터 전송선 이론을 기반으로 계산을 통해 반사손실 (RL)을 도출하였으며, 일부 시료에 대해서는 RL 실측정을 통해 계산된 결과와 잘 맞는 것을 보였다. Co의 치환량 (x)에 따라 고주파 복소 투자율 특성이 변화하였으며 이에 따라 전자기파 흡수 주파수 대역의 조절이 가능하였다. 또한 x = 1.0, 1.25, 1.5 시료에서는 매우 우수한 최대 전자기파 흡수 특성 (RL = -70 ~ -50 dB )을 보이며, 90% 이상의 전자기파 에너지를 흡수 (RL ≤ -10 dB) 하는 주파수 밴드 폭 또한 10 GHz 이상으로 광대역 레이다 흡수가 가능함을 보였다.

• Journal of electromagnetic engineering and science
• /
• 제8권3호
• /
• pp.110-113
• /
• 2008

In this paper, we designed and fabricated an electromagnetic(EM) wave absorber for automotive radar in cars using $TiO_2$ as a dielectric material and chlorinated polyethylene(CPE) as a binder. First of all, we confirmed that the optimum composition ratio of $TiO_2$ was about 70 wt.%. The complex relative permittivity of a sample containing $TiO_2$: CPE=70:30 wt.% was calculated from S-parameter. The EM wave absorption abilities were simulated for the EM wave absorbers of different thickness using the calculated relative permittivity, and the EM wave absorber was manufactured based on the simulated design. A comparison of simulated and measured results is in good agreement. Measurement shows that a 1.85 mm thick absorber has absorption ability higher than 20 dB in the frequency range of $76{\sim}77$ GHz for automotive radars.

• 한국전자파학회논문지
• /
• 제18권10호
• /
• pp.1136-1141
• /
• 2007

본 논문에서 는 Sendust와 $Al(OH)_3$를 이용하여 전파 흡수체를 제작하였으며, 지지재로는 CPE(Chlorinated Polyethylene)를 이용하였다. 주 재료인 Sendust에 $Al(OH)_3$를 0 wt.%, 3 wt.%, 5 wt.%, 7 wt.%만큼 혼합하여 그 특성을 파악하였다. 그 결과 $Al(OH)_3$의 양이 5 wt.%일 때 전파 흡수 특성이 가장 향상되는 것을 알 수 있었다. 그리고 이 특성을 이용하여 적층형 전파 흡수체를 만들었으며, 두께 2 mm인 전파 흡수체가 무선 LAN사용 주파수인 2.4 GHz에서 전파 흡수능 18.5 dB의 특성을 보였다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1993년도 추계학술대회 논문집
• /
• pp.71-74
• /
• 1993

In this paper, the permeability(${\mu}$$\sub$r′/, ${\mu}$$\sub$r"/), permittivity($\varepsilon$$\sub$r′/, $\varepsilon$$\sub$r"/) and absorption properties of Ferroxplana/Rubber composites were investigated. The composite specimens were prepared by molding and curing the mixtures of matrix rubber and Ni$_2$Y ferroxplana powders which were synthesized by coprecipitated method. The permeability(${\mu}$$\sub$r′/) of specimen was decreased in the range of 8∼12.5(GHz) and the permeability(${\mu}$$\sub$r"/) and Permittivity($\varepsilon$$\sub$r′/, $\varepsilon$$\sub$r"/) were increased. The optimum thickness of electromagnetic wave absorber (F/R=4, 1,200($^{\circ}C$) ), utilizing the Smith chart, was about 3.0(mm). The Figure of Merit was 93(%).

• ETRI Journal
• /
• 제38권6호
• /
• pp.1031-1041
• /
• 2016

This paper presents millimeter-wave (mmWave) propagation characteristics and channel model parameters including path loss, delay, and angular properties based on 28 GHz and 38 GHz field measurement data. We conducted measurement campaigns in both outdoor and indoor at the best potential hotspots. In particular, the model parameters are compared to sub-6 GHz parameters, and system design issues are considered for mmWave 5G Giga communications. For path loss modeling, we derived parameters for both the close-in free space model and the alpha-beta-gamma model. For multipath models, we extracted delay and angular dispersion characteristics including clustering results.

• Current Optics and Photonics
• /
• 제2권2호
• /
• pp.179-184
• /
• 2018

Terahertz (THz) wave generation by periodically poled $BaTiO_3$ (PPBT) with a quasi-phase-matching (QPM) scheme based on cascaded difference-frequency generation (DFG) is theoretically analyzed. The cascaded DFG processes comprise cascaded Stokes and anti-Stokes processes. The calculated results indicate that the cascaded Stokes processes are stronger than the cascaded anti-Stokes processes. Compared to a noncascaded Stokes process, THz intensities from $20^{th}$-order cascaded Stokes processes increase by a factor of 30. THz waves with a maximum intensity of $0.37MW/mm^2$ can be generated by $20^{th}$-order cascaded DFG processes when the optical intensity is $10MW/mm^2$, corresponding to a quantum conversion efficiency of 1033%. The high quantum conversion efficiency of 1033% exceeds the Manley-Rowe limit, which indicates that PPBT is an excellent crystal for THz wave generation via cascaded DFG.