• 한국통신학회논문지
• /
• 제35권1C호
• /
• pp.40-44
• /
• 2010

MQASK 디지털 수신기의 타이밍 복원 루프에서는 self-noise의 영향으로 발생하는 타이밍 jitter에 의해 성능이 저하된다. 타이밍 jitter는 타이밍 복원 루프 내에 전치필터를 사용함으로써 해결할 수 있지만, 전치필터에 의해 루프지연이 발생하고, 타이밍 복원 루프의 안정성 및 acquisition 성능이 감소하게 된다. 또한, 전치필터에 의해 타이밍 복원 루프의 복잡도가 증가한다. 본 논문에서는 jitter-free 타이밍 복원 루프에서 전치필터로 인해 발생하는 루프지연을 제거하기 위해 정합필터, resampler, 그리고 전치필터의 기능을 포함한 다상필터 구조의 resampler를 제안하였다. 본 논문에서 제안한 다상필터 구조의 resampler를 사용한 타이밍 복원 루프에서는 타이밍 jitter를 제거하기 위해 사용된 전치필터로 인해 발생하는 루프지연을 해결함으로써 타이밍 복원 루프의 안정성을 향상시키고, 타이밍 jitter를 효과적으로 제거한다. 또한, 타이밍 복원 루프의 구조가 간단해지기 때문에 하드웨어 구현 시에 유리하다.

• Smart Structures and Systems
• /
• 제16권6호
• /
• pp.1147-1167
• /
• 2015

Wireless smart sensors, which have become popular for monitoring applications, are an attractive option for implementing structural control systems, due to their onboard sensing, processing, and communication capabilities. However, wireless smart sensors pose inherent challenges for control, including delays from communication, acquisition hardware, and processing time. Previous research in wireless control, which focused on semi-active systems, has found that sampling rate along with time delays can significantly impact control performance. However, because semi-active systems are guaranteed stable, these issues are typically neglected in the control design. This work achieves active control with smart sensors in an experimental setting. Because active systems are not inherently stable, all the elements of the control loop must be addressed, including data acquisition hardware, processing performance, and control design at slow sampling rates. The sensing hardware is shown to have a significant impact on the control design and performance. Ultimately, the smart sensor active control system achieves comparable performance to the traditional tethered system.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
• /
• pp.516-519
• /
• 2003

3kW photovoltaic (PV) systems and data acquisition system are constructed for performance analysis of PV system at field demonstration test center (FDTC) of Korea. As climatic and irradiation conditions are varied, the performance characteristics of PV system are collected and analyzed in data acquisition system. From these results, the performances of gird-connected power conditioning system (PCS) fur PV system have been evaluated and analyzed. Furthermore, performance indices of grid-connected PCS e.g. output power, efficiency, loss factor, and the other index at the site are reviewed.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
• /
• pp.252-255
• /
• 2000

In this paper, a fast pseudo-noise (PN) code acquisition with novel adaptive architecture is presented in direct-sequence spread- spectrum (DS-SS) systems. Since an existing acquisition system has a fixed correlation tap size and threshold value, this system cannot adapt to various mobile communication environments and results in a low detection probability or a high false alarm rate and long acquisition time. Therefore, if a correlation tap size and a threshold value can be controlled adaptively according to received signals, problems of ail existing system will be solved. The system parameter varies adaptively by using constant false alarm rate (CFAR) algorithm well known in a field of detection and proposed signal-to-noise ratio (SNR) measurement system. By deriving formulas of the proposed system, the performance is analyzed.

• 한국국방경영분석학회지
• /
• 제30권1호
• /
• pp.168-188
• /
• 2004

Integrated Logistic Support (ILS) is a management and technical process whereby all the diverse elements needed to fully operate, maintain, and totally support a materiel system in the field are identified, developed, and deployed simultaneously and on an equal priority with the item of materiel being supported. The test and evaluation (T＆E)of ILS act the important role of reduction of life-cycle cost and keeping of good performance for weapon system. In this article, we suggest the alternatives for improvement in the test and evaluation of ILS during weapon system acquisition. It is hoped that this research is valuable and beneficial to persons related weapon system acquisition, in order to maximize the efficiency of defense acquisition management by reducing the life-cycle cost and enhancing the quality of weapon system.

• 전자공학회논문지A
• /
• 제33A권7호
• /
• pp.44-54
• /
• 1996

In DS/SS systems it is necessary to synchronize the locally generated despreading signal with the received spreading signal to demodulate the received signal. The synch process between the two signals is usually accomplished in two steps : first acquisition then tracking. In this paper, an acquisition system aided by the neural network is proposed for the rapid and exact acquisition in DS/SS. the neural netowrk is composed o fthree-layered perpecptrons and trained by the backpropagation algorithm. The performance of the proposed system is analyzed and compared with ones of conventional systems using the sequential estimation technique under an additive while gaussian noisy channel. In all of th econsidered simulations, the proposed system outperforms conventional systems.

• ETRI Journal
• /
• 제30권4호
• /
• pp.495-505
• /
• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• 지능정보연구
• /
• 제1권2호
• /
• pp.123-137
• /
• 1995

Most of solution methods in scheduling attempt to generate good solutions by either developing algorithms or heuristic rules. However, scheduling problems in the real world require considering more factors such as multiple objectives, different combinations of heuristic rules due to problem characteristics. In this respect, the traditional mathematical a, pp.oach showed limited performance so that new a, pp.oaches need to be developed. Expert system is one of them. When an expert system is developed for scheduling one of the most difficult processes faced could be knowledge acquisition on scheduling heuristics. In this paper we propose a method for the acquisition of knowledge on the selection of scheduling heuristics using Dempster-Shafer Theory(DST). We also show the examples in the multi-objectives environment.

• Journal of Electrical Engineering and Technology
• /
• 제6권5호
• /
• pp.723-730
• /
• 2011

The GPS modernization program offered a new civil signal on the L2 band, and the first modernized GPS Block IIR satellite was launched in September 2005. Currently, eight GPS Block IIRM satellites and two Block IIF satellites transmit L2C signal. The L2C signal contains two codes of CM and CL that are much longer than the L1 C/A code. Thus, the acquisition of the CM and CL codes takes more time compared with that of L1 C/A code. Under the assumption that the L2C signal is strong enough for detection, this paper suggests rapid acquisition methods for the GPS L2C signals for software receivers and compares its performance with that of other methods.

• 한국국방경영분석학회지
• /
• 제36권2호
• /
• pp.53-69
• /
• 2010

국방무기체계획득사업 관리의 목적은 궁극적으로 요구된 성능, 예산, 전력화시기를 충족시키는 것이다. 2006년 출범한 방위사업청은 무기체계 획득사업을 효율적으로 수행하기 위해서 통합사업관리제를 도입하여, 방위력개선사업 관리를 위한 프로젝트 조직이 61개가 운영 중에 있다. 하지만 한국적인 국방획득환경에서의 프로젝트 관리 측면에서 실증적인 분석연구가 미흡한 것이 현실이다. 따라서 본 연구는 무기체계획득사업관리를 하나의 프로젝트로 인식하고, 프로젝트관리 연구에서 제시된 프로젝트 성공요인(CSF : Critical Success Factors)과 무기체계획득사업관리의 관계에 대해서 알아보았다. 연구 결과 전체적으로는 의사소통, 사용자 참여, 명확한 요구사항 변수가 프로젝트 성공에 영향을 주는 것으로 분석되었다. CSF 요소는 사업추진단계별, 사업의 특성, 규모에 따라서 프로젝트 성공에 미치는 영향이 각각 다르다는 것을 실증적으로 증명하였다. 이번 연구 결과를 통해서 통합사업관리팀이 무기체계획득사업 수행 시 사업 단계, 특성, 규모에 따라서 중점 관리 분야를 식별한 것이 이 논문의 의의라고 생각한다.