• 천문학회보
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• 제40권1호
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• pp.51.1-51.1
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• 2015

Over several decades, a historical review of receiver development for radio astronomy in Korea such TRAO, SRAO and KVN will be presented.

• 수산해양기술연구
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• 제35권3호
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• pp.215-226
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• 1999

The experimented rangefinder consist of sets of V/A-Code GPS and sets of L1 C/A-code & carrier phase receivers connected by two spread spectrum radio modems in order to measure relative range and bearing between two ship antennas by real time, comparing and analyzing accuracy of both GPS receivers at the fix point on the land by means of executing zero baseline test by C/A code and by carrier phase as well as measuring distance range 5m, 10m, 15m between each other receivers. The results from the measurement of relative range and bearing are as follows as ;1. According to the results from zero baseline test, the average error by C/A-code receiver is less than 0.1m, which proves theories from published books but when each GPS receivers track different satellites, the range accuracy error becomes up to 100m by means of S/A. Because of this sudden wide range error, rangefinder is not appropriate at relative range measurement without additional modification of the algorism of the GPS receiver itself.2. According to relative range measurement by Carrier Phase and zero baseline test at static condition, the range error is less than 3.5cm in case that it passes more than 5 minutes after GPS sets can track simultaneously more than 6 satellites. Its main reason is understood that the phase center of antenna is bigger than geodetic antenna.3. When range measurement of two receivers from 5m, to 10m to 15m, the each range error is 0.340m, 0.190m, 0.011m and each standard variation is 0.0973m, 0.0884m, 0.0790m. The range error and standard variation are in inverse proportion to distance between two receivers. 4. L1 Carrier Phase GPS generally needs 5 minutes to fix and during this ambiguity search, the relative range and bearing angle is shown to be various.

• 한국멀티미디어학회논문지
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• 제7권7호
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• pp.905-912
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• 2004

세션간 공유 대역폭의 공정성을 위한 연구로 LVMPD(Layered Video Multicast with Priority Dropping)가 있다. 이 기법은 어느 한 세션에서 혼잡 발생 시 공정성에 의해 혼잡이 없는 다른 세션의 최상위 레이어도 같이 드롭된다. 따라서, 혼잡이 없는 세션은 여분의 대역폭이 있음에도 불구하고 대역폭을 효율적으로 사용하지 못한다. 본 논문에서는 공정성에 의해 발생하는 여분의 대역폭을 효율적으로 사용하기 위한 분배 기법을 제안한다. 제안 기법에서는 현재 수신자가 수신하는 최상위 레이어와 요구하는 상위 레이어를 고려하였다. 송신자는 수신자가 혼잡상태 일 때 패킷 제거 우선순위를 부여하고, 혼잡이 없는 세션의 수신자가 상위 레이어를 요구 시 레이어 추가/드롭 플래그에 값을 부여한다. 스위치는 패킷 제거 우선순위가 부여된 패킷을 제거하고, 혼잡이 없는 세션을 위해 레이어 추가/드롭 플래그가 부여된 패킷을 전송한다. 따라서, 혼잡이 없는 세션의 수신자들이 상위 레이어를 추가할 수 있도록 하였다. 실험결과, 제안 기법이 기존 기법보다 세션간 공유 대역폭을 효율적으로 사용함을 알 수 있었다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.235-240
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• 2006

Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Severe effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A L1 C/A software GPS receiver was developed consisting of a RF front-end module and a signal processing program on the PC. The RF front-end module consists of a down converter and a general purpose device for acquiring data. The signal processing program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS L1 C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.

• 전자공학회지
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• 제29권7호
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• pp.51-58
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• 2002

This paper describes functions required for implementation of digital television (DTV) broadcast receivers. The necessary functions for the DTV receiver vary with the transmission media-terrdstrial, cable and satellite. This paper briefly introduces its hardware and software structure, This paper also presents the future of DTV receivers according to the tomorrow's broadcast environment.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.385-390
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• 2006

This paper examines the sampling and jitter specifications and considerations for Global Navigation Satellite Systems (GNSS) software receivers. Software radio (SWR) technologies are being used in the implementation of communication receivers in general and GNSS receivers in particular. With the advent of new GPS signals, and a range of new Galileo and GLONASS signals soon becoming available, GNSS is an application where SWR and software-defined radio (SDR) are likely to have an impact. The sampling process is critical for SWR receivers, where it occurs as close to the antenna as possible. One way to achieve this is by BandPass Sampling (BPS), which is an undersampling technique that exploits aliasing to perform downconversion. BPS enables removal of the IF stage in the radio receiver. The sampling frequency is a very important factor since it influences both receiver performance and implementation efficiency. However, the design of BPS can result in degradation of Signal-to-Noise Ratio (SNR) due to the out-of-band noise being aliased. Important to the specification of both the ADC and its clocking Phase- Locked Loop (PLL) is jitter. Contributing to the system jitter are the aperture jitter of the sample-and-hold switch at the input of ADC and the sampling-clock jitter. Aperture jitter effects have usually been modeled as additive noise, based on a sinusoidal input signal, and limits the achievable Signal-to-Noise Ratio (SNR). Jitter in the sampled signal has several sources: phase noise in the Voltage-Controlled Oscillator (VCO) within the sampling PLL, jitter introduced by variations in the period of the frequency divider used in the sampling PLL and cross-talk from the lock line running parallel to signal lines. Jitter in the sampling process directly acts to degrade the noise floor and selectivity of receiver. Choosing an appropriate VCO for a SWR system is not as simple as finding one with right oscillator frequency. Similarly, it is important to specify the right jitter performance for the ADC. In this paper, the allowable sampling frequencies are calculated and analyzed for the multiple frequency BPS software radio GNSS receivers. The SNR degradation due to jitter in a BPSK system is calculated and required jitter standard deviation allowable for each GNSS band of interest is evaluated. Furthermore, in this paper we have investigated the sources of jitter and a basic jitter budget is calculated that could assist in the design of multiple frequency SWR GNSS receivers. We examine different ADCs and PLLs available in the market and compare known performance with the calculated budget. The results obtained are therefore directly applicable to SWR GNSS receiver design.

• Journal of electromagnetic engineering and science
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• 제16권4호
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• pp.199-205
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• 2016

We present a novel schematic using a 3-dB coupler to transmit radiofrequency (RF) power to two receivers selectively. Whereas previous multiple receiver supporting schemes used hardware-switched methods, our scheme uses a soft power-allocating method, which has the advantage of variable power allocation in real time to each receiver. Using our scheme, we can split the charging area and focus the RF power on the targeted areas. We present our soft power-allocating method in three main points. First, we propose a new power distribution hardware structure using a FPGA (field-programmable gate array) and a 3-dB coupler. It can reconfigure the transmitting power to two receivers selectively using accurate FPGA-controlled signals with the aid of software. Second, we propose a power control method in our platform. We can variably control the total power of transmitter using the DC bias of the drain input of the amplifier. Third, we provide the possibility of expansion in multiple systems by extending these two wireless power transfer systems. We believe that this method is a new approach to controlling power amplifier output softly to support multiple receivers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2371-2388
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• 2015

In this paper, we investigate the performance evaluation of three dimensional (3D) multiple-input multiple-output (MIMO) systems with an adjustable base station (BS) antenna tilt angle and zero-forcing (ZF) receivers in Ricean/Lognormal fading channels. In particular, we take the lognormal shadow fading, 3D antenna gain with antenna tilt angle and path-loss into account. First, we derive a closed-form lower bound on the sum rate, then we obtain the optimal BS antenna tilt angle based on the derived lower bound, and finally we present linear approximations for the sum rate in high and low-SNR regimes, respectively. Based on our analytical results, we gain valuable insights into the impact of key system parameters, such as the BS antenna tilt angle, the Ricean K-factor and the radius of cell, on the sum rate performance of 3D MIMO with ZF receivers.

• 한국위성정보통신학회논문지
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• 제3권2호
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• pp.38-42
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• 2008

2005년 DVB-S2 규격이 최종 마무리 되었지만 이미 보급된 기존의 수많은 DVB-S 수신기는 새로이 완전한 DVB-S2 수신기로 교체되기까지는 여전히 DVB-S 신호는 수신되어야 한다. 이를 위해서 방송사업자는 기존의 DVB-S 수신기에는 DVB-S 신호를, DVB-S2 수신기에는 DVB-S2 신호를 전송해야 한다. DVB-S2 수신기에서 DVB-S서비스를 수용하기 위해서는 DVB-S2 chip에 DVB-S 모듈이 구현되어야 한다. 이런 역호환성을 위해서 시스템에서는 계층적 변조 방식을 적용해야 하며, 시스템 마진을 만족하기 위해 본 논문에서는 편향각에 따른 시스템의 성능을 분석하였으며 또한 성능을 검증해 보았다. 그리고 본 방식을 검증하기 위해서 FPGA chip을 이용하여 테스트베드를 구현하였으며 이를 보인다.

• 수산해양기술연구
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• 제41권3호
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• pp.213-221
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• 2005

In order to get more accurate GPS position with the changes of the inner configuration setting of GPS receiver, the authors carried out measurements of the position at known it with one antenna and two GPS receivers manufactured by same company. We have investigated the accuracies of positions according to the change of the maskangle and receiving mode of output data in inner configuration of GPS receivers, and analyzed the relationships between numbers of satellites visibility and maskangles, and values of HDOP and maskangles. When the maskangles in inner configuration were set below 20 degree, the accuracies of positions were high. But if they were became bigger than 25 degree, standard deviations ot position errors and HDOPS of positions were became bigger. Numbers of satellites visibility(y) and maskangles(x) have relations with a formula, y = -0.1662x+9.9225, and values of HDOP(y) and maskangles(x) have relations with a formula, y = 0.6035 $e^{0.0517x}$. The results of position accuracies observed by two GPS receivers to the known position at same time were that average errors of position fixs by GPS receiver configured with NMEA0183 mode were 6.7m and standard deviations were 1.5m, and them by GPS receiver configured with binary mode were 5.0m and standard deviations were 1.1m respectively.