• International Journal of Automotive Technology
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• 제7권6호
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• pp.703-714
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• 2006

The growing concern surrounding rollover incidences and consequences of Sports Utility Vehicles(SUV) have prompted to investigate the sensitivity of critical vehicle parameters on rollover. In this paper, dynamic rollover simulation of Sports Utility Vehicles is carried out using a validated nonlinear vehicle model in Matlab/Simulink. A standard model is considered and critical vehicle parameters like CG height, track width and wheel base are varied within chosen specified limits to study its influence on roll behavior during a Fishhook steering maneuver. A roll stability criterion based on Two Wheel Lift Off(TWLO) phenomenon is adopted for rollover propensity prediction. Further dynamic rollover characteristics of the vehicle are correlated with Static Stability Factor(SSF), Roll Stability Factor(RSF) and Two Wheel Lift Off Velocity(TWLV). These findings will be of immense help to SUV chassis designers to determine safety limits of critical vehicle parameters and minimize rollover incidences.

• The Journal of the Acoustical Society of Korea
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• 제16권2E호
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• pp.47-54
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• 1997

This paper presents two results on intersymbol interferences in baseband digital communication over an additive white Gaussian noise channel-the interferences due to mismatched square-root raised-cosine filters, in which the filters have different roll-off factors, and / or due to sampling-time jitter. The result for the mismatched filters is that even the jitter-free sampling causes intersymbol interference and it is negligibly small for a wide range of signal-to-noise ratio up to 10dB, for the roll-off factor ranging from 0.2 to 0.5, the mismatch loss being within 0.1dB from the optimum at around 10-6 .For jitter interference an approximation formula for the bit error probability is derived in case of the matched filters, which shows how the roll-off factors and the amount of jitter affect the system performance. The formula is reasonably accurate.

• 한국정보전자통신기술학회논문지
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• 제8권2호
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• pp.101-106
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• 2015

본 논문은 인접 심볼 간의 간섭이 발생하지 않는 최대 데이터 전송률인 Nyquist rate 보다 빠르게 데이터를 전송하여 전송량을 증가시키는 FTN(Faster than Nyquist) 기법을 이용하여 최적의 필터 roll-off 값과 탭 수를 설정한다. FTN 신호 전송 시 발생하는 ISI(Inter-Symbol Interference)를 최소화하기 위해 LDPC부호를 기반으로 하는 터보 등화 모델을 적용하였으며, FTN 신호의 필터 roll-off 값과 탭 수에 따라 시뮬레이션하여 성능을 향상시키고 최적의 값을 설정하였다.

• 한국통신학회논문지
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• 제19권4호
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• pp.624-632
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• 1994

본 연구에서는 DMR(Digital Microwave Radio) STM-1 신호전송을 위한 CCITT G.707SDH(Synchronous Digital Hierachy) 제1레벨인 155Mbps 속도의 64QAM RF MODEM 변조기를 구현하였다. 변조기의 성능을 좌우하는 중요한 특성은 PSF(Pulse Shaping Filter)를 설계하는 일로써, 기존에는 Chebychev 필터(roll-off factor a=0.33, 군지연 10nsec이하를 얻었다. 또한 PSF 통과후 -20dBm, IF 증폭단 통과후 0dBm의 출력레벨을 얻었다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.498-500
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• 2004

QPSK (Quaternary Phase Shift Keying) will be adopted as the modulation of HRIT (High Rate Information Transmission) which is transmitted to COMS (Communication, Ocean and Meteorological Satellite) through HPA (High Power Amplifier) in ground segment. Due to the nonlinearity of HPA, IMD (Inter-Modulation Distortion) of multi-carrier signals and PAPR (Peak-to-Average Power Ratio) of modulated HRIT must be considered to estimate the output power of HPA. In this paper, we measured the PAPR to various the roll-off factor of RRC (Root Raised Cosine filter) which is filtering the modulated HRIT signal for reducing ISI (Inter-Symbol Interference) and bandwidth. It was found that the minimum PAPR is 2.78dB at 0.5 of roll-off factor for scrambled data. It's 2.78dB of P APR will be in output power selecting in COMS earth station.

• ETRI Journal
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• 제46권4호
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• pp.716-726
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• 2024

An ultrawide stopband lowpass filter is reported using three stepped impedance resonators with high selectivity. The filter extends the stopband frequency range and attenuation, and two quarter-wave open stubs and three circular ground slots are introduced. The lumped and distributed equivalent models are derived and analyzed. The corresponding results are validated experimentally in a fabricated prototype. The prototype lowpass filter has a 3 dB cutoff frequency (f_c) of 2.9 GHz, and the stopband is extended up to 35 GHz (12.07f_c), with an attenuation level better than 20 dB throughout. The passband-to-stopband transition (3 dB-20 dB) bandwidth is 0.18 GHz, and the roll-off factor is 135 dB/GHz at 30 dB. The insertion loss is 0.3 dB at 1.6 GHz. The normalized circuit size of the proposed filter with respect to the guided wavelength is 0.04.

• 한국통신학회논문지
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• 제21권11호
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• pp.2942-2953
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• 1996

This paper studies the effect of intersymbol interference due to sampling-time jitter on the worst-case bit error probability in a digital modultation over an additive white Gaussian noise channel, with the squared-root raised-cosine filters in the transmitter and the receiver. It derives approximation formulas using the Taylor series approximations. the principal results of this paper is the relationship between the worst-casse bit error probability, the degree of jitter, the roll factor of the raised cosine filter, and other quantities. Numerical results show, as expected, that the intersymbol interference decreases as the roll-off factor increases and the jitter decreases. They also show that the approximation formulas are accurate for smally intersymbol interference, i.e., for large roll-noise ratio $E_{b/}$ $N_{0}$.leq.7 dB and begin to lose accuracy for larger signal-to-noise ratio.o.o.

• 한국통신학회논문지
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• 제25권5A호
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• pp.634-640
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• 2000

본 논문에서는 OQPSK 신호에 대한 공상 변수(Maximum Likelihood parameter) 평가에 기반을 둔 확장된 DD-DEO(Decision Directed-Decision Estimate) 위상 동기 알고리즘을 제안한다. 제안한 방식은 기존의 방식과 비교할 때, 위상 검출기 블록 전에 I(In-phase), Q(Quadrature-phase)채널 당 2 tap을 가지는 필터 블록을 첨가함으로써, 위상 동기 루프에 입력되는 데이터 의존적인 잡음을 줄일 수 있다. 제안한 방식은 송 수신단 기저대역 필터의 롤오프 요소(roll-off factor), 위성 채널의 백오프(back-off) 그리고 루프 대역(loop bandwidth)을 결정하는 $\beta$를 변화시키며 위상 오차와 오류 확률 관점에서 기존의 방식 및 QPSK와 비교하여 성능 평가를 행하였다.

• ETRI Journal
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• 제23권4호
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• pp.177-189
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• 2001

Multicarrier DS-CDMA is an effective approach to combat fading and various kinds of interference. In this paper, we present an overlapped multicarrier DS-CDMA system, wherein each of the rate 1/M convolutionally-encoded symbols is also repetition coded and transmitted using overlapped multicarriers. However, since the frequency spectrums of successive carriers are allowed to overlap, the transmission bandwidth is more efficiently utilized. The effect of the overlapping percentage between successive carriers of a multicarrier DS-CDMA system on the performance is investigated to determine the overlapping percentage showing the best performance. We suggest two methods for sub-band overlapping variation. One is to allow variation of sub-band overlapping percentage when the total number of subcarriers is fixed. The other is to increase the number of sub-bands (the number of repetitions R) with fixed sub-band bandwidth. Given a total number of subcarriers MR, we show that the BER variation is highly dependent on the roll-off factor ${\beta}$ of a raised-cosine chip wave-shaping filter irrespective of convolutional encoding rate 1/M and repetition coding rate 1/R. We also analyze the possibility of reduction in total multi-user interference by considering the variation of both the roll-off factor ($0<{\beta}{\leq}1$) and the sub-band overlapping factor ($0<{\lambda}{\leq}2$), and show that the proposed system may outperform the multicarrier DS-CDMA system in [3].

• 한국분말재료학회지
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• 제29권2호
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• pp.123-131
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• 2022

The purpose of this study is to improve the mechanical properties and develop manufacturing technology through self-soluble alloy powder flame spray coating on the surface of a run-out table roller for hot rolling. The roller surface of the run-out table should maintain high hardness at high temperatures and possess high wear, corrosion, and heat resistances. In addition, sufficient bonding strength between the thermal spray coating layer and base material, which would prevent the peel-off of the coating layer, is also an important factor. In this study, the most suitable powder and process for roll manufacturing technology are determined through the initial selection of commercial alloy powder for roll manufacturing, hardness, component analysis, and bond strength analysis of the powder and thermal spray coating layer according to the powder.