• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.48-57
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• 1999

안테나 단에서 직접 수신 신호의 디지털화가 이루어지고 그 해당 신호의 처리는 고속 디지털 신호처리기 내에서 소프트웨어로 수행되는 방식을 SWR(Software Radio)이라 한다. 그러나 현재의 기술 수준을 감안하여 보다 현실적인 SDR(Software Defined Radio) 정의가 필요하게 되었다. SDR이란 수신신호의 디지털화가 안테나 이하의 임의의 단(IF단)에서 이루어지는 무선으로 정의된다. 물론 A/D변환기등의 기술이 더욱 발전되면 궁극적으로는 SWR로 진화될 것이다. 그러면 SDR은 왜 필요한 것일까? 현재 사용중인 이동통신 단말기의 단점은 어느 한 표준 또는 방식에 종속되어 언제 어디서나 임의의 시스템에 접속되어 사용하기에는 많은 기술 종속적인 문제 및 제약을 내포하며, 사용방식에 따른 시스템의 유연성이 없고, 상용 서비스 도중에 발생되는 단말기 문제의 해결(recall service)이 어렵고, 많은 기술료를 지불해야 한다는 것이다. 부연하면 CDMA 셀룰라의 경우 퀄컴 등의 특정한 회사에 의해 기술이 폐쇠되어, 정보의 흐름이 자유스럽지 못할 뿐더러, 이로 인해 기술진화가 보다 빠르게 진행되지 못하고, 전세계적으로 많은 새로운 우수 제품의 출연에 제약이 가해진다는 것이다. 따라서 SDR(Software Defined Radion)을 도입, 하드웨어 및 소프트웨어를 개방형 구조(open architecture)로 개발한다면 정보의 흐름을 자유롭게 할 수 있고, 이로 인하여 세계적으로 다양한 신제품의 개발이 촉진되고 결과적으로 전세계 시장이 커지게 되는 일석이조의 효과를 얻을 수 있게 된다. 또한 이 같은 개방형 단말기 개발의 필요성은 최근 시장동향으로 볼 때, 기존의 단말기 회사 입장에서는 새로운 수익 모델이 필요한 시점이고, 또한 2002년경에 판매되는 단말기의 80%정도는 멀티모드타입 단말기일 것으로 예측되는 점, 그리고 금년말까지 100개 회사 이상이 SDR 포럼 멤버로 가입할 것으로 예측되는 점, 무선 인터넷 폭발적인 성장으로 복합 멀티미디어 단말기 시대가 다가오는 점 등으로 미루어 볼 때, 고객의 서비스 가치선택에 역점을 둔 기술을 중시해야 한다는 점에서 더욱 설득력을 지닌다. 따라서 이 같은 목적과 3세대 이동통신 및 인터넷 사용자의 증가, 반도체기술의 발전에 힘입어, 과거 군용 시스템에서 이용되던 SWR 기술을 상용시스템 특히 3세대 이동통신에 적용하려는 연구가 활발히 진행되고 있다. '96년 SDR 포럼이 결성되었는데, 목적은 휴대형 장치(hand-held devices), 기지국(base stations), 차량형 장치(mobile stations)를 포함하는 다중모드(multi-mode), 다중대역(multi-band) SDR을 위한 개방형 구조의 표준을 정하기 위함이다. 이 같이 public forum에 의한 표준(open architecture standard)이 정해지면 그 다음은 이를 어떻게 구현할 것인가가 문제가 될 것이다. 본고에서는 먼저 SDR 단말기 요구사항을 살펴보고, 이 요구사항들을 만족하는 SDR 단말기 구조, SDR 계층참조 모델, 그리고 기존의 단말기 구조와 SDR 계층참조 모델의 연관관계에 대해 살펴보고, 크게 두가지 종류의 단말기 즉 사용 SDR 단말기와 군용 SDR 단말기에 대해 살펴보고, 설계 절차 및 현재 시점에서 단말기 구현을 위해 해결해야 하는 기술적 과제를 살펴보고 결론을 언급한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.464-470
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• 2000

In this paper, we introduce a modified interference cancellation scheme to overcome MAI(Multiple Access Interference) in DS-CDMA. Among ICs(Interference Cancellers), PIC(Parallel Interference Canceller) requires the more stages to have the better BER(Bit Error Rate), and SIC(Successive Interference Canceller) faces the problems of power reordering and large delays. To resolve the problems of them, we propose a modified interference cancellation scheme combining SIC and PIC. The proposed interference canceller has improved the performance through the total received signal applied sorting method is fed into the initial stage. Its structure extracts the good characteristics because of the input signal removed MAI in the initial stage. The characteristics of the proposed system are as follows (1) smaller delay, and the strongest user signal is also reduced to MAI(unlike SIC), (2) it has the good BER performance only using fewer stages (unlike PIC).

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.225-230
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• 2013

In a bandpass sampling (BPS), the frequency of the sampler is lower than that of the signal being sampled. In this method, the baseband spectrum directly appears by the sampling operation, so that it is not necessary to use any frequency down-converter, which makes the receiver's hardware simpler. The second-order BPS uses two identical BPS samplers, of which sampling times are offset by each other. By exploiting the relationship between two sampled signals, it can be possible to cancel the aliased signal component or the interference due to the bandpass sampling. In order to cancel the interference, an interpolant filter is used to manipulate the phase characteristics of the BPS sampled signal. In this paper, it is introduced a multiband interpolant filter which can simultaneously cancel multiple interference signals that have been aliased from multiple frequency bands. In case of no need of interference cancellation, another method is suggested to enhance the signal quality by 3dB. A computer simulation has been performed, and the feasibility of the suggested methods has been verified.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.6
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• pp.53-61
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• 2014

For monitoring the flight trajectory and the status of a launch vehicle, the mission control system in NARO space center process data acquired from the ground tracking system, which consists of two tracking radars, four telemetry stations, and one electro-optical tracking system. Each tracking unit exhibits its own tracking error mainly due to multi-path, clutter and radio refraction, and by utilizing only one among transmitted informations, it is not possible to determine the actual vehicle trajectory. This paper presents a way of generating flight trajectory via post-processing the data received from the ground tracking system. The post-processing algorithm is divided into two parts: compensation for atmosphere radio refraction and multi-sensor fusion, for which a decentralized Kalman filter was adopted and implemented based on constant acceleration model. Applications of the present scheme to real data resulted in the flight trajectory where the tracking errors were minimized than done by any one sensor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.941-944
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• 2015

In this paper study for VSAT(very small aperture terminal) LNB(low noise block). ship LNB was demanded high stability and low noise figure. We designed FEM(Front-End Module) that was operated multi-band. FEM designed was constructed in a multi-band low noise receiver amplifier, a frequency converter, IF amplifier, Voltage Control Oscillator signal generating circuit four circuit using. To convert the multi-band 2.05GHz band, it generates four local oscillator signals, the four(band1, band2, band3, band4) designed to output an IF signal developed conversion apparatus, the conversion gain 64dB, noise figure 1dB or less, output P1dB 15dBm or more, phase noise showed -73dBc@100Hz.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.6
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• pp.141-152
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• 2011

Growing efforts and interests of security techniques in a diverse surveillance environment, the intelligent surveillance system, which is capable of automatically detecting and tracking target objects in multi-cameras environment, is actively developing in a security community. In this paper, we propose an effective visual surveillance system that is avaliable to track objects continuously in multiple non-overlapped cameras. The proposed object tracking scheme consists of object tracking module and tracking management module, which are based on hand-off scheme and protocol. The object tracking module, runs on IP camera, provides object tracking information generation, object tracking information distribution and similarity comparison function. On the other hand, the tracking management module, runs on video control server, provides realtime object tracking reception, object tracking information retrieval and IP camera control functions. The proposed object tracking scheme allows comprehensive framework that can be used in a diverse range of application, because it doesn't rely on the particular surveillance system or object tracking techniques.

• Journal of the Korea Convergence Society
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• v.8 no.11
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• pp.85-91
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• 2017

This paper concerns the design of a matching module system enabling the RF signal to be harmonized between the new base stations (RRH) and the repeater in the same frequency band of the asynchronous transfer network. This matching system controls the RF Gain Control of the module while monitoring the quality of the quality. Additionally, the RF environment has been adapted accordingly to adjust the RF Gain Control to match the receiver characteristics of the relay. As a result of this study, we improved the quality of the interface between the new base stations and existing relays.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.155-161
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• 2015

As the popularity of the smartphone becomes increase, indoor smartphone positioning technology has been actively studied. The acoustic signal generated from the smartphone is received from the several microphones at the relative positioning system, and the trigger signal is proposed to mitigate the multipath effect and the effect is verified. But for the simple trigger method, there would be error occurred according to the variation of the distance or surrounding noise. In this paper, in order to resolve the problems, the dynamic trigger threshold technology is proposed and its effect is verified by the experiment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.2
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• pp.170-177
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• 2011

This paper proposes a telemetering method that transmits the real-time data together with the time-delayed data and that merges both data after flight test. The method can minimize the error data which occur in the communication environment affected by the multipath fading and transmit antenna pattern when telemetry data are received during the flight test. This method was applied to the design of the telemetry unit and the development of data merging program. By merging the resulting data of flight test and analyzing synchronization errors, its efficiency for the telemetry link is verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.429-436
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• 2017

Since the telemetry performance using the time-delayed data dissipates the wireless channel resources, we propose the spectral efficient retransmission scheme in this paper. In the proposed scheme, the telemetry data is retransmitted based on triggered memory to improve the spectral efficiency. The proposed scheme minimizes the error caused by multipath fading, antenna pattern as well as the error caused by the flight events. In the flight simulation data, we show the proposed scheme improves the telemetry performance based on spectral efficient retransmission.