• 한국전자파학회논문지
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• 제12권6호
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• pp.906-911
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• 2001

본 논문에서는 비화 통신을 위하여 chirp 방식을 이용한 BPSK 시스템의 LPI(low probability of intercept)와 AJ(anti jamming) 성능을 분석하였다. Chirp 방식은 주파수를 전체 확산대역 내에서 임의적으로 변화시켜 신호의 주기적인 특성을 제거하기 때문에, feature parameter인 chip rate를 검출하는데 용이한 DAM(delay and multiplier)과 반송파 주파수 검출에 용이한 SC(Squaring Circuit)에 대항하여 뛰어난 LPI 특성을 가진다. chirp parameter의 변화에 따른 LPI 특성으로 chirp duration(Tc)이 커질수록 좋은 LPI 성능을 보인다. PBNJ(partial band noise jammer)환경에서, chirp 방식이 이론적인 DSSS(Direct Sequence Spread Spectrum) 방식에 비하여 AJ 성능이 우수함을 시뮬레이션으로 확인하였다. PBNJ와 MTJ(multi-tone jammer)를 비교하였을 때, chirped BPSK 시스템이 동일 JSR(jammer to signal power ratio)에서 MTJ에 더 우수한 AJ 성능이 있다.

• 대한기계학회논문집B
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• 제32권12호
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• pp.907-914
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• 2008

This study is mainly focused on the assessment of return, semi return, and returnless fuel supply system for an LPi engine. In order to compare the return type with returnless one with various LPG blends, combustion analysis and cyclic THC emission characteristic were tested at the part load operating condition of the LPi engine. Considering heat balance of each fuel supply systems, pressure and temperature increment of return type showed lower at the fuel rail during idle warm up operation. However, those of returnless type at LPG tank maintained stable and slow increment because the heat transfer from the LPi engine was minimized. Finally, hot restartability of each fuel supply systems were evaluated with the various LPG blends and fuel temperatures. As a result, semi return type has equivalent performance to return type considering combustion and emission characteristic, hot restartability performance for LPi engine.

• 한국전자파학회논문지
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• 제12권4호
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• pp.594-599
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• 2001

NRAZ 정보 신호의 기본적인 특징인 symbol rate를 검출하기 위해서는 비선형 특성을 가는 DAM (Delay-And-Multiplier) 수신시를 이용한다. 검출 성능의 척도는 DAM 수신기 출력단에서 얻어지는 rate-line 의 정규화된 SNR 이 주로 사용되며, 비화 통신에서는 LPI(Low Probability of Intercept)를 위하여 이를 낮추어야 한다. 본 논문에서는 DAM 수신기에 대한 LPI 성능을 분석하기 위해 입력 신호로 MSK 계열의 변조된 신호를 사용하였다. 특히, GSM 시스템에 사용되는 GMSK(BT=0.3)을 중심으로 분석하였다. 결과적으로, 대역 효율이 우수한 GMSK 변조 방식이 BPSK, QPSK, OQPSK , 그릭 MSK 변조 방식과 비교하여 좋은 LPI 성능을 갖는다. 분석의 공정성을 위하여 사용대역 내에서의 송신전력을 같게 하였다.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.99-105
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• 2007

Currently, BLDC fuel pump was applied on LPi vehicle using 3rd fuel supply system as liquified phase LPG injection method had already shown better performance than others. Its cost, however, is rather expensive because of drawbacks such as complicated structure, a fault of localization of system. In this work, demonstration system for a developed turbine type fuel pump to replace BLDC system was setup and investigated. This study results that fuel mass flow rate of turbine type pump and injection performance of injector were better compared to BLDC type. Comparing flow rate of summer LPG with that of winter LPG, the flow rate decreased about 25% using winter LPG. Performance applying turbine type LPi fuel pump to engine is confirmed.

• 한국군사과학기술학회지
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• 제5권1호
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• pp.119-126
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• 2002

본 논문에서는 chirp 변조를 이용한 통신 시스템의 LPI(low probability of intercept)와 AJ(anti-jamming)성능을 분석하였다. 인터셉터에 DAM(delay and multiplier)과 SC(squaring circuit)가 이용된 경우 CBPSK(Chirped BPSK)의 LPI 성능을 분석하였다. 스펙트럼 확산 방식의 CBPSK와 DS/BPSK 시스템에 대한 AJ 성능을 비교 분석 및 주파수 호핑 방식의 FH/CBFSK(Chirped BFSK)와 FH/BFSK, 그리고 FH/BCM(Binary Chirp Modulation) 시스템에 대한 AJ 성능을 분석하였다. LPI 결과로, CBPSK(Chirped BPSK)은 chirp 변수인 chirp 주기($T_3$가 커질수록 좋은 LPI 성능을 보인다. AJ 결과로, PBNJ(partial band noise jammer)환경에서 CBPSK 방식이 DS/BPSK 방식에 비하여 AJ 성능이 우수하고, 마찬가지로 FH/CBFSK 방식이 FH/BFSK 방식에 비하여 AJ 성능이 우수함을 시뮬레이션으로 확인하였다.

• 에너지공학
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• 제14권3호
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• pp.187-193
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• 2005

In this study, the performance and emission characteristics of a liquefied petroleum gas (LPG) engine converted from a diesel engine were examined by using mixer system and liquid propane injection (LPi) system. A compression ratio of 21 for the base diesel engine, was modified to 8, 8.5, 9 and 9.5. The engine performance and emissions characteristics are analyzed by investigating engine power, brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), volumetric efficienry, CO, THC and NOx. Experimental results showed that the LPi system generated higher power and lower emissions than the conventional mixer fuel supply method.

• 대한기계학회논문집B
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• 제28권9호
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• pp.1075-1080
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• 2004

In this study, performance and emissions characteristics of an liquefied petroleum gas (LPG) engine converted from a diesel engine were examined by using mixer system and liquid propane injection (LPi) system fuel supply methods. A compression ratio for the base diesel engine, 21, was modified into 8, 8.5, 9 and 9.5. The cylinder head and the piston crown were modified to roe the LPG in the engine. Ignition timing was controlled to be at minimum spark advance for best torque (MBT) each case. Engine performance and emissions characteristics are analyzed by investigating engine power, brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), volumetric efficiency, CO, THC and NOx. Experimental results showed that the LPi system generates higher power and lower emissions than the conventional mixer fuel supply method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3323-3328
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• 2007

Conventional LPG pump for Liquified Petroleum injection(LPi) engine has been adopted vane type. But the BLDC type fuel pump for LPi system has complicated structure and its price is high. Therefore, as a alternative, this study has mainly focused on the development of turbine type LPG pump which has lower cost and simple structure than conventional BLDC type. To verify the possibility of substitute the performance tests were performed for each fuel pump. The comparative items were pressure settling time, variation of fuel outlet temperature and engine performance of hot restart ability. As a result, performances of turbine type LPG pump were equivalent or high comparing to the BLDC type all over the tests for different fuel composition.

• Journal of electromagnetic engineering and science
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• 제4권2호
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• pp.63-67
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• 2004

DAM(Delay-And-Multiplier) intercept receiver usually detects the symbol rate of the transmitted DS spread spectrum signal for the feature extraction. It is important for secure communication to reduce the normalized output signal-to-noise ratio that is generated at the DAM intercept receiver as a measure of detectability. In this paper, several kinds of chip waveforms are novelly analyzed for LPI(Low-Probability of Intercept) communication against DAM intercept receiver. Consequently, it is shown that the rectangular chip waveform shows the best LPI performance in the bandwidth of 2/$T_c$TEX>, 4/$T_c$TEX>, and 6/$T_c$TEX>/. Except the rectangular waveform, kaiser chip waveform show better LPI performance than the other waveforms in the bandwidth of 4/$T_c$TEX> and 6/$T_c$TEX>.

• 오토저널
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• 제27권3호
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• pp.14-18
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• 2005