• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.761-769
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• 2009

In this paper, we report on the channel capacity and diversity gain of the vehicle on-glass antenna for FM radio reception. The correlation coefficient and channel capacity were obtained using the simulated 3D radiation pattern of each antenna and the Rayleigh channel model for urban environment. To examine the channel capacity we used two antennas which are a simple straight antenna and L-type antenna. Then we observed the available channel capacity by varying the position of feeds and the shape of the L-type antenna. The sample antenna, which has a maximum feed distance with different polarizations, was built and the receiving performance was measured in the weak FM field area. From the results we confirmed that the distance between the feeds should be placed as far as possible for the high channel capacity. If the distance between the feeds are greater than a certain threshold value than the polarizations of the two antennas are getting more important for determining the channel capacity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.291-298
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• 2017

In this paper, we derive the achievable degrees of freedom (DoF) for multiple-input multiple-output (MIMO) Z-interference channels (Z-IC) with reconfigurable antennas at the receivers, assuming that channel state information is not available at the transmitters. We propose a new linear scheme to align interfering signals and to decode desired signals through the designed preset mode switching pattern of reconfigurable antennas at the receivers. The key idea of our scheme is to use interfering signals as a side information at the interfered receiver by being silent at the corresponding transmitter during some time slots. Consequently, it is shown that the reconfigurable antennas at the receivers can bring a DoF gain if the number of preset modes is greater than the number of RF chains at the receivers.

• The Journal of the Acoustical Society of Korea
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• v.31 no.2
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• pp.107-113
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• 2012

In this paper, we have analyzed the performance of space diversity technologies using experimental data in order to analyze the usability of space diversity techniques in underwater channel environments. After analyzing the experimental data we found out that high diversity gain should not be expected when using a stationary transmitter with a stationary receivers in swallow underwater channel. And we also find out that the distance between sensors should be at least 8 wavelengths apart to take advantage of diversity gain in underwater moving channel environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.462-468
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• 2012

In this paper, an adaptive digital automatic gain control(AGC) algorithm with two stages is proposed. AGC technique is crucial for mobile communication equipment because path loss in wireless channel and gain fluctuation in receiver front-end continuously change the received signal strength. Furthermore, adaptive criteria should be applied to the design of AGC algorithm in order to support many waveforms with one SDR communication device. With these reasons, a two-stage structure is proposed to satisfy both flexibility and adaptiveness. Compared with conventional method, it also requires shorter convergence time. Numerical results show that the gain value of variable gain amplifier(VGA) is converged within proper time and proposed scheme controls the input level of analog to digital converter(ADC) to be stable during long range of time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.924-934
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• 2018

This paper describes the development and measurement results of C-band planar active phase array antenna for detecting and tracking radar(weapon-locating radar). The antenna is designed with 14 sub-arrays(12 main channels and 2 sidelobe blanking channels and approximately 3,000 elements of transmit-receive channel) to generate transmit and digital receive patterns. Using a near-field measurements facility, G/N, transmit patterns, and received patterns are measured. Receive patterns are implemented with digital beamforming by signal processing. The measurement results demonstrate that antenna design specifications were fulfilled.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.113-119
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• 2010

In this paper, the considered cognitive radio system has a pair of PT-PR and a pair of ST-SR. In first time slot(1 Phase), PT broadcast signal $x_p$ to PR, ST and SR. Then, each receivers(PR, ST, SR) decode received signal $x_p$. In second time slot(2 Phase), ST combine decoded signal ${x_p}^{\prime}$ and signal $x_s$, and it broadcast combined signal to PR and SR. PR and SR decode combined signal. At this time, PR can achieve diversity gain, due to using MRC, it combine 'received and decoded signal ${x_p}^{\prime}$ at 1 phase' and 'detected signal $x_p$ at 2 phase'. SR use linear combining technique and it can obtain $x_s$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.522-529
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• 2002

MMIC circuits in whole receiver system was fabricated based on GaAs pHEMT technology. And a V-band downconverter module was fabricated by integrating these circuits. The downconverter module consists of a LO drive power amplifier which generates 24dBm output power, a low noise amplifier(LNA) which shows 20 dB small signal gain, an active parallel feedback oscillator which generates 1.6 dBm output power, and a cascode mixer which shows over 6dB conversion gain. The good conversion gain performance of our mixer made no need to attach any IF amplifier which grows conversion gain. Measured results of the complete downconverter show a conversion gain of over 20 dB between 57.5 GHz and 61.7GHz without IF amplifier.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.3
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• pp.53-59
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• 2000

A received signal in mobile communication environments exhibits variation in both amplitude and phase due to the multipath fading. Therefore we analyzed the performance of DS/CDMA(Direct Sequence/code Division Multiple Access) DPSK(Differential Phase Shift Keying) system for the variations of PLL(Phase Locked Loop) gain with Tikhonov probability density function, assuming that the phase difference between transmitter and receiver signals is phase error. As a result, it is discovered that the performance of system could be improved by the control of PLL gain in compared with the DPSK system which does not consider the phase error. If the PLL gain is 1dB, the difference of two systems is 4.8dB and 0.4dB at 7dB. and if 30dB, it coincides. From above, it

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.464-473
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• 2012

In this paper, we derive the gain of network coding when it is utilized for retransmission in wireless networks. To the end, we derive the outage probability of the network-coded transmission and express the diversity order as a function of the number of nodes and the node's listening probability. From the outage probability, we formulate the ${\epsilon}$-outage capacity. The network-coding gain is the ratio of the ${\epsilon}$-outage capacities between network-coded and non-coded transmissions. Under our system model, we find that the network-coding gain is a function of the diversity order. Moreover, when there are infinitely many nodes, we show that the network coding gain approaches $0.25{\epsilon}^{-1}$.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.130-132
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• 2011

본 논문은 지상파 방송망 내 전계강도가 낮은 지역에 최소한의 데이터 전송률을 보장하기 위한 계층변조와 다중경로 채널 극복 및 수신 성능 향상을 위한 다중 안테나 수신기법을 SFN에 적용하여 제안하였다. 계층변조는 기존의 데이터 스트림에 부가적인 데이터 스트림을 삽입함에 따라 지상파 3D HDTV 방송 서비스는 더 많은 유효 전송률을 확보하고 고품질 비디오 서비스를 제공할 수 있었다. 그러나 기본 서비스의 품질을 유지하면서 부가적인 서비스의 품질을 보장하기 위한 대책이 필요하다. 그래서 송, 수신 안테나의 이득을 올리기 위해 다중 안테나 사용 방식을 채용하고, 그 수신 성능을 다중 안테나 위치에 따라 비교해 보았다. 그 결과, 수신 안테나가 한 쪽의 송신 안테나에 가까워질수록 실질적인 SNR이 증가하여 BER 성능이 향상되는 것을 확인하였다.