• Journal of the Korea Institute of Military Science and Technology
• /
• v.19 no.5
• /
• pp.582-589
• /
• 2016

Multi-mode monopulse system is widely used for satellite terminal like UAV because of high tracking accuracy and low size/weight profile. In order to calculate tracking error, Multi-mode monopulse system utilizes high-order mode signal, and it should have enough C/N(carrier to noise) level therefore tracking system needs narrow band filtering of received satellite beacon signal as much as possible. However, UAV suffers for beacon frequency drift derived from Doppler effect due to satellite figure 8 movement and UAV maneuvering. Therefore wideband signal processing needs to be considered in advance for exact doppler compensation and consequent time delay. In this paper, we propose the multi-stage Digital Signal processing system for beacon signal, which could minimize the signal delay under high Doppler and low C/N condition.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2012.07a
• /
• pp.225-227
• /
• 2012

무선 사운드 스피커는 서로 다른 위치에 배치되어 송신기와의 채널 환경이 서로 다르게 되어 송신기와의 거리가 상대적으로 먼 후방 스피커의 경우 사람이나 구조물에 의해 채널 환경이 열악하게 되어 전방 스피커에 비해 데이터 오류 발생 확률이 높다. 본 논문은 Multi-band orthogonal frequency division multiplexing (MB-OFDM) 기반의 무선 오디오 전송 시스템에서 무선 채널 환경이 우수한 스피커에서 무선 채널 환경이 열악한 스피커로 데이터를 전달하는 스피커 릴레이 기법을 사용할 때, packet error ratio (PER) 성능을 향상시키며 전송 시간을 감소시킬 수 있는 효율적인 스피커 릴레이 기법을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.7A
• /
• pp.682-687
• /
• 2010

The IEEE 802.15.4a specification targets the low-rate (LR) Impulse-radio (IR) ultra-wideband (UWB) system which is now widely applied in the WPANs considering rather short distance communications with low complexity and power consumption. The physical (PHY) layer uses concatenated coding with mixed binary phase-shift keying and binary pulse-position modulation (BPSK-BPPM), and direct sequence spreading with time hopping in order that both coherent and non-coherent receiver architectures are supported. In this paper, the performances of multiple access schemes compliant with IEEE 802.15.4a specification are investigated with energy detection receiver, which allow avoiding the complex channel estimation needed by a coherent receiver. However, the performance of energy detection receiver is severely degraded by multi-user interference (MUI), which largely diminishes one of the most fascinating advantages of UWB, namely robustness to MUI as well as the possibility to allow parallel transmissions. So as to improve the performance of multiple access schemes, we propose to apply the novel TH sequences as well as to increase the number of TH positions. The simulation results show that our novel multiple access schemes significantly improve the performance against MUI.

• Journal of Korea Multimedia Society
• /
• v.9 no.1
• /
• pp.51-58
• /
• 2006

In this paper, we evaluated Ultra Wideband MC-CDMA system which is the combination of DS-CDMA and OFDM systems, which have been drafting in current standardization for IEEE802.15.3a. Too many Rake Fingers are demanded in the DS-CDMA system to detect multi-path signals, which results in high system complexity. OFDM system fails to qualify for FCC certification unless frequency hopping is off. MC-CDMA has lower complexity compared to DS-CDMA and shows good performance against frequency selective fading. In addition, for a wide-band communication, less radio power per spectrum is allowed in the MC-CDMA system than in an OFDM system. The MC-CDMA system is analyzed by a numerical formula and compared with DS-CDMA and OFDM by a computer simulation.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.3 no.2
• /
• pp.53-57
• /
• 2008

This paper designed and fabricated the printed dual monopole antenna with CPW feeder for PCS and UWB(Ultra-Wide Band) band. In this paper, modified dual monopole antenna is proposed transform conventional monopole antenna to get dual band frequency. The dual monopole antennas have dual band, broad bandwidth and omni-directional radiation patterns, as it is the conventional monopole antenna. As one monopole operated a stub to match feed line with antenna, we are obtained easy an ideal impedance matching. It is increased band width of impedance. The antenna bandwidth is about 1350MHz (1.69~2.04[GHz]z]) at 1st resonance frequency, 2,670MHz (4.33~6[GHz]) at 2nd, resonance frequency, and, 3,980MHz (6.1~10.08[GHz]) at 3th resonance frequency on VSWR$$\leq_-$$2, and then we can be got not only 1.75~1.87 [GHz] PCS band but also, UWB band.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.8C
• /
• pp.806-813
• /
• 2009

This paper presents a modem chip design for high-speed wireless communications. Among the high-speed communication technologies, we design the UWB (Ultra-Wideband) modem SoC (System-on-Chip) Chip based on a MB-OFDM scheme which uses wide frequency band and gives low frequency interference to other communication services. The baseband system of the modem SoC chip is designed according to the standard document published by WiMedia. The SoC chip consists of FFT/IFFT (Fast Fourier Transform/Inverse Fast Fourier Transform), transmitter, receiver, symbol synchronizer, frequency offset estimator, Viterbi decoder, and other receiving parts. The chip is designed using 90nm CMOS (Complementary Metal-Oxide-Semiconductor) procedure. The chip size is about 5mm x 5mm and was fab-out in July 20th, 2009.

• Journal of Satellite, Information and Communications
• /
• v.11 no.4
• /
• pp.107-113
• /
• 2016

In this paper, we suggest a design method of a wide-band Butler matrix working at 5.9 GHz for V2X communication antennas. Since V2X communication needs beam-forming and beam-steering antennas to make transportation systems, mobile comm platforms, saturated frequency-resources, and signal TX-and-RX smart, multi-functional, resolved, and efficient utmost, respectively, the proper Butler matrix and its radiating elements as a low-profile geometry are realized. The constitutive components of the basic Butler matrix of a narrow band are designed first. And then, it is extended to a wide-band version to make its frequency-shift less affected by the event of the antenna system being mounted on a car body. The beam-forming and beam-steering performance is presented as the common feature tagged along with the different bandwidths of the frequency responses as the comparison between the narrow- and wide-band cases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.12
• /
• pp.1113-1119
• /
• 2013

In this letter, a new approach is proposed for the design of a multi antenna for MIMO wireless devices. The proposed antenna covers various LTE(Long Term Evolution) service bands: band 17(704~746 MHz), band 13(746~787 MHz), band 5(824~894 MHz), and band 8(880~960 MHz). The proposed main antenna consists of a conventional monopole antenna with an inverted L-shaped slit for wideband operation. The proposed the LTE sub antenna is based on a switch loaded loop antenna structure, with a resonance frequency that can be controlled by capacitance of a logic circuit. The tuning technique for the LTE Rx antenna uses a RF MEMS(Micro-Electro mechanical system) to match the impedances to realize the bands of interest. Because the two proposed antennas are polarized orthogonally to each other, the ECC(Envelope Correlation Coefficient) characteristic between two antennas was measured to be very low (below 0.06) with an isolation characteristic below -20 dB between the two antennas in the operating overall LTE bands. The proposed antenna is particularly attractive for mobile devices that integrate LTE multiple systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5A
• /
• pp.494-499
• /
• 2008

In this study, a Software Defined Radio(SDR) technology-based digital filtering technique applicable to a multiple channel processing system such as a wireless mobile communication system using Code Division Multiple Access(CDMA) technology is proposed. The technique includes a micro-processor to redesign Finite Impulse Response(FIR) filter coefficients according to specific system information and to download the filter coefficients to one digital Band Pass Filter(BPF) to reconfigure another system. The feasibility of the algorithm is verified by implementing a multiple channel signal generator that is reconfigurable to other system profiles, including those for a CDMA system and a WCDMA system on identical hardware platform.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.64 no.3
• /
• pp.116-120
• /
• 2015

In this paper, a step type driver dipole antenna with a tapered balance and unbalance (balun) by a coplanar waveguide (CPW) to coplanar strip (CPS) transition is proposed. The proposed antenna consisted of step type driver, a CPW to CPS transition and tapered balun. The proposed antenna is realized the multi and wide resonate frequency band to introduce the step type driver and tapered balun. The step type driver is acted as a director too. This antenna could be more easily designed than the conventional printed quasi-Yagi dipole antenna. The operating frequency bandwidth was 650 [MHz] (2.65~3.3 GHz), 900 [MHz] (4.7~5.6 GHz) under a return-loss criterion of less than 10 dB. The measurements of the proposed antenna exhibited good results in the wideband operating frequency and radiation pattern. The proposed antenna can support wireless communications applications.