• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.368-377
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• 1999

In this paper, the wide-band CDMA transmitter for 2 GHz band is designed and implemented. The CC-OQPSK implemented as ASIC has better spectral and power efficiency than the conventional QPSK system because it has constant envelope characteristics. Good harmonics rejection characteristics and gain of 20 dB are shown on the intermediate frequency stage using double-conversion scheme. The output power of two-stage RF amplifier is +2l.14 dBm in 1.9 GHz band. It is confirmed that the electrical characteristics of the transmitter satisfy with required the specification of the wide-band CDMA transmitter for 2 GHz band.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.289-294
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• 2008

Affordable traffic capacity of each node in networks is expected to reach in Tb/s range in proportion to the rapid growth of Internet users. To transmit more than Tb/s per fiber pair, WDM should be used as well as existing TDM. To increase the capacity of transmission in WDM networks, there are two ways, increasing channel speed or channel quantity. To increase the channel quantity, there are two ways, narrow spacing or expanding transmission bandwidth. To expand bandwidth, ultra-broadband optical amplifier technology is necessary. In this paper, we introduce EDFA in effect at C/L band, FRA, and some optical amplifiers in effect at S band, and analyze the development trend of various amplification technologies.

• Journal of IKEEE
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• v.20 no.1
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• pp.54-60
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• 2016

In this paper, out-of-band emission regulations and measurement methods of terrestrial DTV broadcasting services are analyzed, and a novel method to evaluate the out-of-band emission characteristics of DTV transmitter is proposed. Experimental results show that proposed method can be easily used to measure the characteristics of DTV transmitter with inexpensive measuring equipments. With a few modifications, proposed method can be widely adopted to measure the RF performances of the general radio equipments efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.8
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• pp.713-718
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• 2013

In this paper, additional data transmission scheme was proposed based on SSB-OFDM Communication system which was know as efficient technique for bandwidth, because it used only single side band instead of double side band. When sending additional data which should be well spreaded for low power characteristics and error robustness. Gold code was selected for spreading code because it has excellent low-cross correlation characteristics. Through computer simulation, the validity was proved that proposed system is well worked with SSB-OFDM system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.344-347
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• 2013

본 고에서는 AM과 FM라디오의 디지털방송 전환을 위하여 현재 사용 중인 방송대역에서의 IN-BAND 방식 외에도 VHF 하위대역 혹은 VHF상위대역을 사용하는 OUT-Of-BAND 방식에 대해 각 전송방식의 장단점을 분석하였다. 그러나 현재 디지털라디오뿐만 아니라 TV도 UHDTV 도입을 위해 VHF상위대역 주파수 사용을 원하고 있어 DMB와 라디오와 TV의 차세대방송 주파수 요구가 상호 충돌이 예상된다. 그러므로 본 고에서는 FM의 디지털라디오 전환방법으로 VHF하위대역(TV채널 5번과 6번)에서의 OUT-Of-BAND 방법에 의한 DRM+ 전송방식 적용을 제안하고 있다, 중파라디오의 디지털방송도 동일 계열 DRM 기술 적용으로 수신기를 값싸게 제조하고 빠르게 보급함으로써 디지털라디오의 활성화 방안을 제시하고 있다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.7
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• pp.30-37
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• 2002

In this paper, we propose a new adaptive slot assignment algorithm called In-VDSA in order to guarantee the QoS(Quality of Service) of VBR(Variable Bit Rate) traffics in wireless ATM and maximize efficiency in use of wireless channels. In the proposed algorithm, the status of terminal buffers is encoded in signed number on the GFC(Generic Flow Control) field of an ATM cell header and piggybacked. And also, the number of slots to be assigned to the next frame is adjusted effectively, which is different to methods in the conventional slot assignment algorithms. As a result, we can guarantee QoS such as CLR(Cell Loss Rate) and cell delay and achieve the higher utilization of channels. The validity of the proposed algorithm has been justified in performance by analysis through simulation results using the BONeS tool and comparison with conventional methods.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.41-45
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• 2015

In this paper, the single port dual-band resonator for magnetic resonance wireless power transfer is proposed. The proposed dual-band resonator is consists of 20 turns spiral coil, a single loop, matching circuit, lumped elements, and a single port. The two sides of the matching circuit are connected to via holes. The spiral coil is operated at MF-band and single loop is operated at HF-band, respectively. We use two of the same structure resonators and simulated and the power transfer efficiency was calculated. The efficiency of simulation and measurement is above 60% at the MF and HF bands, and the distance is 100 mm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.401-407
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• 2009

The multi-band (MB) ultra-wideband (UWB) communication system divides its available frequency spectrum in 3.1 to 10.6GHz into 16 sub-bands, which leads to inherent disparities between carrier frequencies of each sub-band. For instance, the highest carrier frequency is 2.65 times higher than the lowest one. Since the propagation loss is proportional to the square of the transmission frequency, the propagation loss on the sub-band having the highest carrier frequency is approximately 7 times larger than that on the sub-band having the lowest carrier frequency, which results in disparities between received signal powers on each sub-band. In this paper, we propose a novel correlation scheme for frequency hopping (FH) MB UWB communications, where the correlation time is adaptively adjusted relative to the sub-band, which reduces the disparity between the received signal energies on each sub-band. Such compensation for lower received powers on sub-bands having higher carrier frequency leads to an improvement on the total average bit error rate (BER) of the entire FH MB UWB communication system. We analyze the performance of the proposed correlation scheme in Nakagami fading channels, and it is shown that the performance gain provided by the proposed correlator is more significant as the Nakagami fading index n increases (i.e., better channel conditions).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.331-337
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• 2016

In this paper, we analyze performances of in-band full-duplex communication system and self-interference (SI) suppression methods in environment where there exists the SI signal. The SI has to be removed to achieve required error rate performance of the system in order - propagation domain, analog domain and digital domain. In propagation domain, the SI signal is attenuated by separating transmitted and received beams physically. In analog and digital domain, after reconstruction of the SI signal using channel estimates and transmit signal, the SI signal can be cancelled from the desired signal. In this paper, assuming that the SI signal can be sufficiently reduced in propagation domain, we demonstrate that the in-band full-duplex communication system can achieve the target error rate by suppressing the SI signal in order - analog and digital domain, based on channel estimates that can be obtained by the method of Least squares.

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.178-188
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• 2009

In this paper, we propose the method which provides efficient sub-channel allocation for handoff and new call supporting multi-media service in AMC-based OFDMA system. Firstly, we apply the multi-band method which provides different AMC method according to the location of user terminals. Also, in OFDMA system environment that a base station has a lot of sub-channels, we adopt the sub-channel allocation scheme that provides a higher priority to handoff call and real-time service about handoff and new calls with multi-meida service. The simulation results show that the proposed scheme plays a role in increasing the number of new and handoff calls meeting the required blocking rate.