• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.10
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• pp.879-882
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• 2021

The telemetry standard adopts SOQPSK-TG with excellent power and bandwidth efficiency as a modulation technique, and LDPC code with excellent performance as an error correction code. The SOQPSK-TG transmitter consists of a precoder and a CPM modulator. Rather than implementing each receiver separately, the reception performance is improved by combining the trellis and implementing it as a Viterbi decoder. In this paper, the reception performance of LDPC-encoded SOQPSK-TG was evaluated by replacing the Viterbi decoder with a max-log-map decoder capable of soft metric output. As a result of computer simulation in AWGN channel, there is an Eb/No performance gain of about more than 0.7~0.8dB compared to the conventional method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.203-205
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• 2019

위성항법시스템의 안정적인 정보 제공의 요구사항은 점차 증가하고 있지만, 의도적인 전파교란 및 자연환경에 의하여 성능이 저하된다. eLoran 시스템은 위성항법시스템의 단점을 보완하기위한 대표적인 지상파항법시스템으로 고출력 신호로 의도적인 전파교란에 강인한 장점이 있다. eLoran 시스템에서 사용자는 E-field 또는 H-field 2가지 종류의 수신 안테나를 사용 환경에 따라 적합한 것을 사용한다. 접지가 필요없고 상대적으로 주변 전자장비의 잡음에 강인한 H-field안테나는 두 개의 루프로 구성되어 루프간의 위상과 이득차이로 일정한 원형의 지향성을 가지지 못한다. 그러므로 수신한 신호의 방향에 따라 측정치의 변화가 발생하므로 H-field 안테나를 사용시에는 수신하는 신호의 방향에 따른 오차를 제거해야한다. 본 논문에서는 H-field 안테나와 송신국간의 기하학적 방향오차에 따른 오차를 제거하기 위한 후처리 필터를 제안하였다. eLoran 모의 신호생성기를 활용하여 오차를 분석하고 모델링하여 제거하는 기법을 개발하였다. 제안한 기법을 검증하기 위하여 시뮬레이션과 차량실험을 통하여 오차를 확인하고 제거하여 성능향상을 확인하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.21-27
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• 2019

In this paper, we investigate the secrecy outage probability when using a partial relay selection scheme in cooperative communication systems based on decode-and-forward with multi-relay. It is assumed that both the receiving node and the eavesdropping node receive signals at both the transmitting node and the relaying node. The two received signals are used to obtain the diversity gain using the MRC scheme. In this paper, we compute the theoretical formula of secrecy outage probability and compare the theoretical value with the simulation value to prove that equation is valid. The simulation results show how the secrecy outage probability varies with the number of relays.

• Information and Communications Magazine
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• v.28 no.8
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• pp.34-41
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• 2011

최근의 스마트폰의 보급으로 높은 전송률의 다양한 멀티미디어 서비스가 요구되는 추세이며, 이러한 사용자 단말의 서비스 품질을 보장하기 위해 작은 셀 반경을 갖는 많은 기지국들이 필요하게 되었다. 작은 셀 반경을 통해 사용자 단말과 송신기 사이의 거리를 줄이려는 노력과 더불어 릴레이협력 통신을 통해 전송률을 높이고 수신 성능을 높이려는 연구가 활발하게 진행되고 있다. 본 논문에서는 사용자 단말들이 불규칙하게 분포되어 있는 셀룰라네트워크 환경에서 사용자 단말간 협력 통신을 통한 성능 이득을 고찰한다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.175-178
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• 2000

본 연구에서는 CDMA단말기용 Receiver MMIC를 설계하였다. 전체회로는 저잡음 증폭기, 하향 주파수 혼합기 그리고 중간주파수 증폭기로 구성된다. 또한 문턱전압과 전원전압의 변화에 대해 회로의 안정성을 높이는 바이어스 보상회로를 추가하였다. 설계시 높은 선형성과 저잡음 특성을 가지도록 토폴리기를 구성하였고 설계 결과 전체 이득은 28.5dB, 저잡음 증폭기의 입력IP3는 8dBm, 하향주파수 혼합기의 입력 IP3는 0dBm이며 전체회로의 소모전류는 22.1mA이다. 레이아웃된 전체회로의 크기는 1.4$\times$1.4 [$\textrm{mm}^2$] 이다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.10
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• pp.758-765
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• 2018

This paper presents a 24-GHz frequency-modulated continuous wave(FMCW) radar transceiver with two Rx and one Tx channels in 65-nm complementary metal-oxide-semiconductor(CMOS) process and implemented it on a radar system using the developed transceiver chip. The transceiver chip includes a $14{\times}$ frequency multiplier, low-noise amplifier, down-conversion mixer, and power amplifier(PA). The transmitter achieves >10 dBm output power from 23.8 to 24.36 GHz and the phase noise is -97.3 GHz/Hz at a 1-MHz offset. The receiver achieves 25.2 dB conversion gain and output $P_{1dB}$ of -31.7 dBm. The transceiver consumes 295 mW of power and occupies an area of $1.63{\times}1.6mm^2$. The radar system is fabricated on a low-loss Duroid printed circuit board(PCB) stacked on the low-cost FR4 PCBs. The chip and antenna are placed on the Duroid PCB with interconnects and bias, gain blocks and FMCW signal-generating circuitry are mounted on the FR4 PCB. The transmit antenna is a $4{\times}4$ patch array with 14.76 dBi gain and receiving antennas are two $4{\times}2$ patch antennas with a gain of 11.77 dBi. The operation of the radar is evaluated and confirmed by detecting the range and azimuthal angle of the corner reflectors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.941-950
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• 2011

In this paper, we analysis the end-to-end performance of the incremental cooperative communication with relay selection. In the conventional cooperative scheme, the source(S) broadcasts the signal to the relay(R) and the destination(D) at 1st phase, and the R forwards the signal to the D at 2nd phase. Although this scheme can improve performance and provide diversity gain, it suffers from decreasing spectrum efficiency. In order to overcome this problem, the incremental cooperative model can be used. In this paper, we study two incremental cooperative method : the first uses ARQ with threshold SNR and the second uses HARQ with channel coding. we also evaluated performance of the incremental cooperative communication based on the R arrangement by using both methods.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.9-15
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• 2013

Recent works on ad hoc network study have shown that achievable throughput can be made to scale linearly with the number of receive antennas even if the transmitter has only a single antenna. In this paper, we propose a non-parametric linear minimum mean square error (MMSE) receiver for achieving further gain in performance when the channel state information at receiver (CSIR) of interferers is imperfect. The key feature to make our approach effective is to exploit the autocorrelation of the received signal. In fact, by incorporating the desired channel information on top of the observations including interference and noise only, the proposed method achieves large fraction of the optimal MMSE transmission capacity without transmission rate loss. From the SINR analysis as well as transmission capacity simulations in realistic ad hoc network system, we show that the proposed non-parametric linear MMSE receiver brings substantial performance gain over existing multiple receive antenna algorithms.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.75-80
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• 2011

In the cooperative communication, The relay that transmit signal to destination can achieve diversity gain. But transmitter and relay must have own frequency to transmit signal to destination. If Relay is secondary user and does not have own frequency, relay can't transmit signal to destination. So, To analysis performance of cognitive radio We need to consider detection probability of secondary user. In the paper we propose cooperative communication system considering detection probability. And to compare proposed system and conventional, we also simulate incremental cooperative communication. Through the simulation result, we can know that BER performance of proposed scheme is better than incremental relaying in the cognitive radio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1606-1616
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• 2004

This paper introduces a technique for generating an appropriate template signal via modeling of minimum-phase stable ARMA (Auto-Regressive Moving Average) system for coherent impulse communication systems. It has been well known that the transmitted impulse signal becomes deformed because of dispersive and resonant characteristics. Accordingly, in spite of using ideal template signal at the correlator, these impairments degrade overall performance attributed to low level of coherence. To increase the degree of coherence, our proposed scheme realizes A3U system derived by Gaussian pulse signal, which simulates the overall characteristic of transfer function in between transmit and receive wideband antennas so as to generate an appropriate template signal in a form of output. The performance of proposed scheme will be shown in results from computer simulations to verify its affirmative impact on impulse communication system with regarding several distinctively shaped antennas.