• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.233-237
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• 2017

The dual-channel receiver MMIC which is composed of LNA, Mixer, LO-amp and temperature compensation circuit is designed on a single chip. For the performance comparison, a FMCW radar transceiver module using commercial MMICs is also implemented. As a result, Multi-channel Transceiver using manufactured MMIC shows an improved performance such as noise figure and gain flatness compare to purchased MMIC.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.2
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• pp.87-92
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• 2009

In this paper, we designed and fabricated the active amplification block for the integrated antenna module. The fabricated amplification module have a proper gain and low noise figure in the band of AM/FM band, T-DMB band and GPS band, and show good isolation performance for each band. Manufactured circuits satisfied the gain performance 7 dB in AM band, 11 dB in FM band, 10 dB in T-DMB, and 17 dB in GPS band. The integrated amplification block was realized by 35 mm*35 mm size, and was shown as the same sensitivity performance as compared with a conventional reference antennas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1205-1213
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• 2006

In this paper, we analyze the IQ(In-phase/Quadrature) imbalance effects at both transmitter and receiver side of OFDM(Orthogonal Frequency Division Multiplexing) and show that IQ imbalance is the parameter to improve the performance using ML and OSIC scheme. Especially, we can archive the diversity gain due to the IQ imbalance in multipath fading environment. In addition, new preamble format is proposed, which enable estimation of the channel and IQ imbalance parameters to maximize the diversity gain. Significant performance improvement is achieved by using the ML(Maximum Likelihood)and OSIC(Ordered Successive Interference Cancellation) with compensation compared to a standard receiver with no compensation for IQ imbalance and proposed channel estimation scheme achieves the better performance improvement than conventional.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.78-84
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• 2012

In this paper, we introduced the design technique about a Ka band receive module for millimeter wave seekers. The receiver module consists of a waveguide, circulator and transition for antenna connection, and a limiter and gain control amplifier for receiver protection. This module is comprised of a sum, azimuth and elevation channel for receiving monopules signal, and a SLB channel for the acquisition of jamming signal. In this paper, receiver gain and range of gain control dependent on ADC nonlinear characteristic was analyzed and designed for wide dynamic range receive. In the test result of the fabricated Ka-band receive, the frequency band is 1 GHz, the noise figure is as low as 8.2 dB, the gain is $56{\pm}2dB$, the dynamic range is 135 dB, the gain congtrol is more than 86 dB, the channel isolation is more than 35 dB.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.218-226
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• 2022

The main characteristics of the underwater acoustic channel have varying multipath and fast fading. Especially, Frequency Shift Keying (FSK) signals with multiple frequency bands caused loss of information bits allocated on the specific frequencies due to selective fading phenomenon. Therefore, this paper proposes frequency gain control algorithm based on preamble error rates. The proposed algorithm estimates optimal gain value in the range of preamble error rate with less than 10 % for specific faded frequency. By employing turbo equalized FSK signals with rate of 1/3, the experiment was conducted on a lake in Munkyeong city with distance of 300 m to 500 m. The result confirms that packets are decoded successfully by applying proposed algorithm as increasing number of iterations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1737-1743
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• 2006

OCR(On channel repeater) provides the high frequency reuse efficiency for allocating frequency bands to repeaters because the frequency of input and output signals of OCRs is the same. However the oscillation probability of OCRs is high due to the same input and output frequency. In order to prevent a repeater from oscillating, we must keep the antenna isolation higher than the gain of the repeater with a some margin. In this paper we simulated the effects of the amplitude, phase and time delay of feedback signals (m the characteristics of non-regeneration OCR. Simulation results show that the highest probability of oscillation is occurred when the gain of a repeater is the same value of the isolation. From the simulation results, we know that the phase of feedback signals can be adjusted to reduce the possibility of oscillation if a non-regeneration repeater has a narrow operation bandwidth or a signal bandwidth is narrow. As the time delay increases, the probability of oscillation and the fluctuation of gain over a certain frequency band increase also. The effects of the amplitude and phase of feedback signals on S/N of 8-VSB signal for generation and non-generation repeater were tested. The measured results show that the set-top can receive 8-VSB signal when the received signal power is $17{\sim}18dB$ higher than the noise power. When the isolation is almost same as the gain of the repeater, then the set-top can not receive 8-VSB signals due to the oscillation of the repeater. And the phase of feedback signals affects S/N at the output of the repeater when the isolation is $11.75{\sim}13.75dB$ larger than the gain of the repeater. In this case the set-top can not receive 8-VSB signal of at $48^{\circ}\;and\;347^{\circ}$ of the phase of feedback signals. However the phase of feedback signals can not affect the S/N of 8-VSB signals of the generation repeater because of the demodulation and modulation process of the generation repenter. The set-top can not receive 8-VSB signals when the amplitude of feedback signals is $12.6{\sim}13.6dB$ larger than the wanted signal power at the input port of the repeater. It's because that the amplitude of feedback signals saturates the front end of the repeater.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.12
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• pp.777-779
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• 2014

In this paper, we consider IOTA-OFDM/OQAM system that improves the transmission power and rate efficiency of conventional OFDM system and propose DF relaying cooperative communication scheme based on the IOTA-OFDM/OQAM system. In the proposed scheme, the destination receives orthogonal signals from source and relay simultaneously and combines using MRC. We demonstrated that the proposed schemes get better BER performance than conventional system because of the diversity gain.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.209-212
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• 2002

본 논문에서는 위성방송 수신용 광대역 저잡음 증폭기를 설계 및 구현하였다. 전산모의 실험용 소프트웨어를 사용하여 저잡음 증폭기를 설계하였고, 제작된 저잡음 증폭기의 전기적 특성을 네트워크 분석기와 Noise Figure 분석기를 사용하여 측정하였다. LNA단의 Noise Figure에 중점을 두고 샘플을 제작하여 측정한 길과 전산모의실험에서 나온 데이터는 0.46㏈이하였고 전체 시스템에서 측정된 Noise figure는 0.6㏈정도의 좋은 길과를 나타내었지만, 반면에 이득과 반사손실의 결과가 약간 떨어짐을 보였다 위성 인터넷 등 위성을 이용하는 통신 인구의 급격한 증가와 더불어 구현된 저잡음 증폭기를 사용한 LNB(Low Noise Block down converter)가 널리 응용될 것으로 기대된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.49-50
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• 2013

In wireless environment, to provide more efficient service area is need to maintain proper location of wireless LAN AP. Since structural effect corresponding to location of arbitrary scatterers must be considered. Using FDTD method, an obstacle in scattering field should be considered and its diffraction effect for some cross wall is estimated between transmitter and receiver point.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1803-1811
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• 2001

In this paper, Forward Error Correction(FEC) that is satisfied with ITU-T Recommendation J.83, Annex B(North American Data Over Cable Service Interface Specifications(DOCSIS) for Multimedia Cable Network System(MCNS)) is analyzed. The FEC consist of Reed-Solomon(RS) layer, interleaving layer, randomization layer, and trellis coded modulation(TCM) layer. The effects of quantization of input symbol and of trace-back depth in the Viterbi decoder are simulated over AWGN channels.