• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.505-511
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• 2003

In this paper, a driving amplifier stage with 1 Watt output has been designed and fabricated, which is operating at UHF band( 470 ∼ 806 MHz) for digital TV repeater. In the driving amplifier stage, preamplifier and 1 Watt unit amplifier are integrated by one electric substrate which is 2.53 in dielectric constant and 0.8 mm thickness. When the driving amplifier stage is flown by bias voltage of 28 V DC and current of 900 mA. it has the gain of more than 53.5 dB. the gain flatness of $\pm$0.5 dB and return loss of less than -15 dB in 470 ∼ 806 MHz. Also, when two signals at 2 MHz frequency interval are input port into the driving amplifier stage with 1 Watt output, it resulted in excellent characteristics to designed specification with showing intermodulation distortion characteristics of more than 48 dBc.

• Journal of Broadcast Engineering
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• v.12 no.5
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• pp.516-524
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• 2007

In order to use limited frequency resources efficiently, a single frequency network using digital on-channel repeater(DOCR) has been studied and would be implemented. The DOCR generates strong pre-ghosts to ATSC DTV receivers. The forward filter of equalizer in ATSC DTV receivers compensates the distortion made by pre-ghosts. This process induces noise enhancement and colored noise, thereby results in the performance degradation. In this paper we propose to use a dual-feedback equalizer to combat strong pre-ghosts. The proposed equalizer has two feedback filters. One is the decision feedback filter and the other is non-decision feedback filter. The additional non-decision feedback filter decreases the noise by whitening the noise and preventing the generation of colored noise in pre-ghost channel. Thus the equalization technique of dual-feedback structure has performance enhancement in pre-ghost channel in comparison with conventional decision feedback equalizer(DFE). By simulation we analyzed the performance enhancements of DTV receiver using dual-feedback equalization structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.296-303
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• 2008

Co-existence of various wireless systems may cause frequency interference problem. For this reason, frequency sharing studies play a very important role in order to use limited spectrum resources efficiently. Especially, because a satellite system covers a global area in nature, the frequency sharing between the satellite system and terrestrial systems is essential. For satellite systems using Ka bands, we can increase spectrum efficiency by considering off-axis angles of earth station antenna. In this paper, we demonstrate the analysis result of separation distance between the satellite earth station and a terrestrial repeater, and the presented results can be used to design and implement Ka band wireless systems.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.830-844
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• 2010

In this paper, we propose an equalization digital on-channel repeater (EDOCR) with a feedback interference canceller (FIC) for single frequency network of the ATSC terrestrial DTV system. The proposed EDOCR with FIC does not have only high output power by cancelling feedback signals caused by insufficient antenna isolation through the FIC, but also shows better quality of output signals than the conventional on-channel repeaters (OCRs) by removing multipath signals existing between the main transmitter and the OCR, and residual feedback signals through an equalizer. In addition, computer simulations are provided to figure out the superior performance of the proposed EDOCR with FIC.

• Journal of Broadcast Engineering
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• v.7 no.1
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• pp.10-20
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• 2002

In order to fill the gaps in DTV coverage, KBS Technical Research Institute has researched on DTV on-channel repeating systems as well as DTV translators. The on-channel repeater can reuse frequency resources for expanding service coverage. but it has also many restricts in applications for ATSC DTV system. Thiss Paper compares two kinds of DTV on-channel repealer systems and also presents field test results of both systems. From these results, we Infer their characteristics and summarize the conditions and possibilities of the application for our broadcasting networks.

• Journal of Broadcast Engineering
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• v.10 no.2
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• pp.210-220
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• 2005

This paper presents and analyzes laboratory test results of Equalization Digital On-Channel Repeater (EDOCR) using ATSC(Advanced Television Systems Committee) terrestrial digital TV broadcasting system. The EDOCR laboratory test, which is done at CRC(Communications Research Centre) Canada, is classified to receiver test, transmitter test, and synchronization test between transmission and reception frequencies. The receiver part includes feedback signal, random noise, single echo, multi-path ensemble, and NTSC/DTV interference test. The transmitter part includes out-of channel emission, quality of transmitting signal, and phase noise test. By the field test results, the receiver part of the EDOCR eliminates average 5.5 dB of feedback or single echo signal in range of 0 to 11 ${\mu}s$ and has average 18.6 dB at TOV(Threshold of Visibility) under random noise environment. Also, the transmitter part of the EDOCR satisfies the specification of US FCC(Federal Communications Commission), and frequency difference between transmitter and receiver is zero.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.422-427
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• 2005

In this paper, Doherty amplifier is designed by the need of improving the linearity and efficiency of wireless network and repeater for WCDMA. It is designed to maintain the high linearity and efficiency at the low efficiency period of the power amplifier after analyzing Doherty technique using the active load-pull in condition of the high efficiency power amplifier implementation according to the variation of input power. CW 1-tone experimental results at the WCDMA frequency 2.11$\~$2.17 CHz shows that Doherty amplifier, which achieves pore. add efficiency(PAE) 50$\%$ at 6dB back off the point from maximum output power 52.3dBm, obtains higher efficiency of 13.3$\%$ than class AB. finding optimum bias point after adjusted gate voltage, Doherty amplifier shows that IMD3 improves 4dB.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.618-627
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• 2005

In this paper, we have compared and analyzed the performance of high amplifier using Doherty technique to improve linearity and efficiency of base station and repeater Power amplifier for WCDMA. This Doherty amplifier implements with 3dB branch line coupler and $90^{\circ}C$ transmission line The phase offset line is designed to maintain the high linearity and efficiency at the low efficiency Period of the power amplifier CW 1-tone experimental results at the WCDMA frequency $2.11{\sim}2.17GHz$ shows that Doherty amplifier which achieves power add efficiency(PAE) of 50% at 6dB back off the point from maximum output power 52.3 dBm, obtains higher efficiency of 13.3% than class AB Finding optimum bias Point after adjusted gate voltage, Doherty amplifier shows that $IMD_3$ improves 4dB.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.157-162
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• 2011

In this study, we design and implement a cavity filter for the Korea T-DMB broadcasting transmitter station and repeater system. HFSS 3 dimensional field simulation tool is used for this study. T-DMB filter has to be high quality factor Q, and cavity filter is applying in T-DMB system due to high handling power. We use HFSS simulation tool for design to obtain exact resonant frequency with easy design. A cavity filter is implemented based on the simulated results, and test results are compared with simulations. Measured resonant frequency and bandwidth are 211.8MHz and 0.1MHz, and correspond with design values.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.6
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• pp.91-97
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• 2011

In this study, we design and implement a cavity filter for the Korea T-DMB broadcasting transmitter station and repeater system. HFSS 3 dimensional field simulation tool is used for this study. T-DMB filter has to be high quality factor Q, and cavity filter is applying in T-DMB system due to high handling power. We use HFSS simulation tool for design to obtain exact resonant frequency with easy design. A cavity filter is implemented based on the simulated results, and test results are compared with simulations. Measured resonant frequency and bandwidth are 211.8MHz and 0.1MHz, and correspond with design values.