• Journal of Sensor Science and Technology
• /
• v.25 no.3
• /
• pp.189-195
• /
• 2016

In this paper, we newly introduce a visible light communication (VLC) repeater using the LED array in an LED lamp. The LED array is used for a light source in the repeater, which radiates light both for illumination and data transmission. A VLC repeater is made by adding some electronic circuits to the LED array including a photodetector, a demodulator, and a modulator. The repeater is installed on the ceiling of a room like a conventional LED lamp, receives the VLC signal from an arbitrary transmitter, recovers data, and radiates the signal to wide area in the room. We used a carrier frequency of 100 kHz for the uplink from a transmitter to the repeater, and 500 kHz for the downlink from the repeater to a receiver. The repeater is useful for increasing the transmission path to wide area over the obstacles that may exist between VLC transmitters and receivers.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2002.11a
• /
• pp.177-181
• /
• 2002

In this paper, the cancellation or suppression of the feedback interference from Tx antenna using the same frequency is studied. The major problems on the wireless communication system using the same frequency or on-frequency repeater (OFR) are the coupling and isolation between Rx and Tx antenna. In order to increase the isolation between Rx and Tx antenna and to Prevent the self-oscillation of the receiver system, this paper is verified the possibility of the application of interference cancellation system and proposed the design method of the OFR using interference cancellation system.

• 한국정보통신설비학회:학술대회논문집
• /
• 2006.08a
• /
• pp.35-38
• /
• 2006

Using the repeaters is indispensable to WiBro services. Repeater types are distinguished by usage, output power and required performance. In the paper, we have studied on the WiBro digital optic repeater design which has excellent performance characteristic than any other repeaters. WiBro has specific characteristic on modulation method TDD(Time Division Duplex)/OFDMA(Orthogonal Frequency Division Multiple Access) so that it demands specified H/W to design WiBro repeater. Switching technique has been introduced because of TDD characteristic in each amplifier on the repeater. Time Advance technique has been considered because of OFDM characteristic among RAS(Radio Access Station) and repeater. In this paper, we have studied on these techniques to increase repeater cell coverage and distance between RAS and repeater.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.10
• /
• pp.1737-1743
• /
• 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 Transactions of the Korean Institute of Electrical Engineers P
• /
• v.67 no.4
• /
• pp.221-226
• /
• 2018

In this paper, the power transfer efficiency analysis based on the resonant repeater in a magnetic resonance wireless power transfer system is proposed. The efficiency of the magnetic resonance method was verified by comparing the general frequency with the resonance frequency. The resonance repeater was arranged to increase the efficiency and increase the transfer distance. When using resonant repeaters, the maximum efficiency increase is about 36.23[%] and the transfer distance was extended to more than 20[cm]. Through this study, confirmed the effect of using resonance repeaters in wireless power transfer system. As a result, it can be expected that the overall technology related to wireless power transfer system will be more valuable for energy-IT technology.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.37-40
• /
• 2003

The 1.63㎓, 2.33㎓ dual-band PLL frequency synthesizer has been developed for applications to the miniature repeater. The miniature dual-band repeater will be used at shopping mall, basements and underground parking lots. The in-loop 1.63㎓, 2.33㎓ dual-band PLL frequency synthesizer has been developed by designing Si BJT VCO and PLL loop circuits with Colpitts. The prototype of 1.63㎓, 2.33㎓ dual-band PLL frequency synthesizer of size 19${\times}$19${\times}$8(mm) has shown operating frequencies of 1.63㎓, 2.33㎓ ranges, RF output of 1dBm(PCS), 1dBm(IMT-2000), phase noise of -100 dBc/Hz(PCS), -95dBc/Hz(IMT-2000) at 10KHz offset, harmonics suppression of -24dB c(PCS), -15dBc(IMT-2000).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7A
• /
• pp.725-733
• /
• 2006

In this paper, we propose an algorithm which makes the frequency of output signal synchronize with frequency of input signal in Equalization Digital On-channel Repeater (EDOCR) system which was proposed to overcome the disadvantage of conventional Digital On-Channel Repeater (DOCR). Also, we verify the algorithm by using the mathematical equivalent model and analysis the performance by implying the algorithm to EDOCR. The main idea is to use the frequency offset information, which comes from carrier recovery in the receiving part of EDOCR, when the demodulated symbol is re-modulated in transmitting part. Based on the proposed algorithm, EDOCR not only makes the output signal synchronized with input signal in frequency but also emit the output signal which satisfies the ATSC transmission standard without additional equipments such as Global Positioning System (GSP).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.12
• /
• pp.1252-1263
• /
• 2009

In this paper, in order to improve a service quality and to broaden the service coverage in the mobile communication system a study on a digital RF repeater employed with an Interference Cancellation System(ICS) is performed. The digital RF repeater employed with an ICS is implemented to remove interference and feedback signals which are disadvantages of a conventional(or general) RF repeater. This thesis presents the design and experiments of the new wireless repeater. The proposed wireless repeater consists of a RF repeater mounted with digital engine. The digital ICS engine consists of a DSP and FPGA. The digital engine and RF circuit are designed into a one-piece. After developing hardware through the digital platform they are also designed and fabricated into a one-piece in order to apply a best performance repeater system. The method of removing interference and feedback signals is an adaptive IF technique employed with a LMS algorithm. The powerful performance and fast convergence speed is obtained by using this method.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.6
• /
• pp.295-302
• /
• 2011

In this paper we consider technological requirements to broadcast digital television signals using single frequency networks(SFN) in the Advanced Television Systems Committee(ATSC) transmission systems and propose Interference Cancellation Digital On Channel Regenerative Repeater(IC-DOCR) thar overcomes the limitation of EDOCR(Equalization Digital On Channel Repeater) proposed by ETRI. The proposed IC-DOCR maintains the benefits of EDOCR that have good output signal quality removing multi-path, additive white Gaussian noise(AWGN). In additional, since the Interference Cancellation algorithm using the 8-VSB symbol demodulation of received signal removes the Interference of feedback signal, IC-DOCR improve the weakness of EDOCR that have low isolation between receive and transmit antenna so that can overcome the limitation of output signal power. we did analysis and verification of the proposed system performance using computational simulation.

• ETRI Journal
• /
• v.31 no.4
• /
• pp.357-364
• /
• 2009

In this paper, we propose a novel equalization on-channel repeater (OCR) with a feedback interference canceller (FIC) to relay terrestrial digital multimedia broadcasting signals in single frequency networks. The proposed OCR not only has high output power by cancelling the feedback signals caused by insufficient antenna isolation through the FIC, but also shows better output signal quality than the conventional OCR by removing multipath signals existing between the main transmitter and the OCR through an equalizer. In addition, computer simulations and laboratory test results demonstrate that the proposed OCR successfully cancels feedback signals and compensates channel distortions and provides a higher quality transmitting signal with higher output power than conventional OCRs.